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253 Cards in this Set
- Front
- Back
Types of water in soil |
Hygroscopic , Combined, Gravitational, Capillary |
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____________ water is held very tightly around soil particles by adhesive forces |
Hygroscopic |
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Meaning of hygroscopic water |
water held very tightly around soil particles by adhesive forces |
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Meaning of combined water |
Water present in form of hydrated oxides of Al,.Si, etc. |
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What is combined water? How much of it available to plants? |
Hygroscopic and combined. Not available to plants |
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Meaning of gravitational water |
Due to gravitational force, some amount of water goes beyond through the large pores between soil particles, goes beyond the reach of roots of plants and reaches the water table |
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Which type of water is available to plants? |
Capillary water |
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What is capillary water? |
In between small, colloidal soil particles, very small spaces (capillaries) are present. The water in this spaces is known as capillary water available for absorption. |
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Diffusion is obvious in ____________. Give reason- |
Gases and liquids due to high KE |
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Define Simple Diffusion |
Movement of ions, atoms, or molecules of solutes, liquids or gases from region of hugher concentration to region of lower concentration till equilibrium is reached. |
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Which of Diffusion, facilitated diffusion and active transport is not dependent on living system? |
Diffusion |
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In diffusion, particles move in a ____________ fashion. |
Random |
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Comment on probability of diffusion w.r.t. solids. |
Diffusion in solids is more likely than diffusion of solids |
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Why is diffusion very very important in plants? |
It is the only means for gaseous movement within body |
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Factors affecting diffusion rates |
1. Concentration gradient 2. Permeability of separating membrane 3. Temperature 4. Pressure 5. Size of substances |
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Diffusion pressure is (cause/ result) of diffusion |
Cause |
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Define diffusion pressure |
Potential ability of solid liquid or gad to diffuse from an area of its greater concentration to an area of lesser concentration |
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DP proportional to - |
Number of diffusing molecules |
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Effects of adding solutes to water |
DP reduces |
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What is DP of pure water? |
1236 (Maximum) |
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What is facilitated diffusion? |
Selective transport of large molecules across cell membrane assisted by special proteins (porins) without expenditure of energy |
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Water soluble substances are transported across membranes by ___________ ___________ aquaporins. |
8 different |
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Diffusion of a substance across cell membrane primarily depends on its _______________. |
Solubility of lipids |
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Which substances diffuse through cell membrane faster? |
Fat soluble/ Hydrophobic |
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Which substances find difficult to diffuse through cell membrane ? |
Substances that have a hydrophilic moeity |
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Porins facilitate diffusion by setting up a concentration gradient - True or False giving reasons |
False - They do set up a gradient, a gradient should already be present |
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How do porins help in transport? |
The proteins form channels in the membrane for molecules to pass through. Some channels are always open others can be controlled. |
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Give types of passive transport with meaning |
Symport - 2 molecules in same direction Anti port - 2 molecules in Opp. Direction Uniport - 1 molecule membrane independently |
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Factors increasing active transport |
Higher rate of respiration - more ATP - more salt accumulation |
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Factors reducing active transport |
Respiratory inhibitors, Low O2 content |
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What the proteins used for active transport known as? |
Pumps |
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Transport from lower to higher concentration to lower concentration also known as - |
Uphill transport |
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Compare diffusion, facilitated diffusion and active transport w.r.t. to above points |
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Water has ________________ so it can move up by capillary action. |
High surface tension |
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Water has ________________ which enables to form a continuos stream of water. |
High tensile strength |
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Water has high ____________, ____________, ____________, hence it acts as temperature stabilizer. |
Specific heat, heat of fusion, heat of vaporization |
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Water has high Specific heat, heat of fusion, heat of vaporization so it can act as _____________. |
Temperature stabilizer |
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In what activities is water required w.r.t. reproduction and gaseous exchange? (4) |
Movement of gametes, stomatal movements, dehiscence of fruits, germination of seeds |
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How does water help aquatic plants? |
Transparent, so light passes - photosynthesis |
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Percentage of water in 1. Watermelon 2. Most herbaceous plants |
1. 92% 2. 10-15% of fresh weight as dry matter |
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Is a seed actually dry? Give reason |
No, it has water. Otherwise, it wouldn't be alive and respiring |
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Give amount of absorption of water by 1. A mature corn plant 2. Mustard plant |
1. About 5 L/ day 2. = Body weight / 5 hr |
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Water is a limiting factor for _____________ and ____________ in both ____________ and ___________ environments. |
Plant growth, productivity, agricultural, natural |
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Examples of membranes 1. Freely Permeable 2. Semi Permeable 3. Selectively Permeable 4. Impermeable |
1. Cell wall 2. Parchment paper, Egg membrane 3. Cell membrane, tonoplast 4. Suberin in cork and endodermis, cuticle |
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What do the following membranes allow to pass? 1. Freely Permeable 2. Semi Permeable 3. Selectively Permeable 4. Impermeable |
1. Solvent, solute 2. Solvent 3. Solvent, some selected solutes 4. None |
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Water always goes from _________ to ___________. |
Hypotonic to hypertonic |
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Concentration of solution is given by _______________. Its unit is ______________. |
Osmolarity, milliosmoles/litre |
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Formula of osmolarity |
Moles of solute / volume of solvent in litres |
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Define osmosis |
Diffusion of water or solvent from a solution of lower concentration to a solution of higher concentration or from pure solvent to solution through semi-permeable membrane |
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Type of surrounding solution for following condition 1. Turgid 2. Flaccid 3. Plasmolysed |
1. Hypotonic 2. Isotonic 3. Hypertonic |
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What happens when cell is kept in - 1. Hypotonic 2. Hypertonic 3. Isotonic |
1. Endosmosis - Turgid 2. Exosmosis - Plasmolysed 3. No net flow - Equal in and out - Flaccid |
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In plant cells, the _____________ contributes to solute potential of cell. |
Vacuolar sap |
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In plant cells, the vacuolar sap contributes to ___________ of cell. |
solute potential |
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At equilibrium, both cell and surrounding should have same ______________. |
Water potential |
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Which is the most accepted mechanism used for Translocation of sugar from source to sink? Who put it forward? |
Pressure/ mass flow hypothesis by E. Munch |
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Process of mass flow hypothesis |
Glucose - Sucrose - Companion cells - Sieve tube (active transport) - hypertonic - water from xylem - OP increase - decrease at sink - active transport - glucose - energy use - water to xylem |
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Loading of phloem sets up a __________________ that facilitates _______________ in phloem. |
Water potential gradient, mass movement |
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Which experiment is used to identify the tissues through which food is transported? |
Girdling |
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What is done in girdling? |
On the trunk of a tree, ring of bark upto a depth of phloem layer is removed. |
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Girdling shows that _________ is the tissue responsible for Translocation of food and that transport takes place in _______ direction. |
Phloem, one (Note: in this experiment, it shows unidirectional, answer is not wrong) |
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Since the source-sink relationship is ________, (depending on _____________) direction of movement in phloem is bidirectional. |
Variable, season or plant's needs |
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Movement in phloem is _________ directional. |
Bi |
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Compare C3 and C4 plants in terms of efficiency of carbon fixation into sugar |
C4 are twice efficient than C3 |
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Compare C3 and C4 plants in terms of water loss during photosynthesis (CO2 fixation) |
C4 loses only half as much water as C3 for same amount of CO2 |
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Environmental factors affecting transpiration |
Temperature, light, humidity, wind speed |
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Effect of humidity on transpiration |
More humidity less transpiration |
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Least transpiration occurs at _____________ humidity. |
100% relative |
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Plant factors affecting transpiration |
Number and distribution of stomata, percent of stomata open, water status of plant , canopy structure, etc. |
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Transpiration driven ascent of xylem sap depends mainly of following properties of water: |
Cohesion, Adhesion, Surface Tension, Tensile Strength, Capillarity |
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Cohesion, Adhesion, Surface Tension give water high __________ and high __________. |
Tensile strength, Capillarity |
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Measurements reveal ghat forces generated by transpiration can create pressures sufficient to lift xylem sized column of water over ___________ high. |
130 m |
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Who called transpiration necessary evil and unavoidable evil respectively? |
Curtis, Steward |
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Mesophyll with intercellular spaces and stomata are essentially meant for ___________, but the _____________ is unavoidably responsible for transpiration. |
Gaseous exchange, leaf anatomy |
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Benefits of transpiration (key words) |
1. Cooling effect 2. Mineral Nutrition 3. Water movement 4. Optimum turgidity |
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Which benefit of transpiration has exception? The exception is related to _____________. |
Optimum turgidity, succulent plants |
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Transpiration cools surface by ____________ degrees by ___________. |
10 to 15, evaporative cooling |
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Transpiration supplies water for __________________. |
Photosynthesis |
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Transpiration maintains _________________ of plants by keeping cells turgid. |
Shape and structure |
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Each gram of water adsorbs ______________ heat from leaf and its environment. |
580 cal |
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Transpiration is important for miner Nutrition because - |
Minerals are transported through transpiration stream |
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Transpiration provides an efficient means of ____________ and ___________ of salts absorbed by roots. |
Transport and distribution |
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Water absorbed is translocated through xylem vessels in a ______________. |
Continuous water column |
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Transpiration maintains ___________ in cells. |
Optimum degree of turgidity |
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Plants cells function best when there is some water __________ (deficit/excess) |
Deficit |
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How much amount of water absorbed is lost through transpiration? What is the effect? |
98%, large amount of energy wasted |
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Transpiration causes water deficit and plants suffer from ___________ due to ______________. |
Injury, dessication |
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If amount of water lost exceeds the amount of water absorbed, then it causes ____________. |
Wilting of leaves |
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What cannot be explained by transpiration? |
Movement of food |
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Succulent plants store water in _______________. |
Special water storage tissues |
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Stomata movement are brought by changes in ____________. |
Volume and shape of guard cells |
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Guard cells absorb water from ____________. |
Subsidiary cells |
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What happens to the shape of guard cells when they absorb water? |
Pressure on walls causes thin outer wall to bulge out and inner walls to crescent shape |
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Who proposed the proton transport concept? It explains ____________. |
Levitt, mechanism of opening and closing of stomata |
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According to proton transport concept, the opening and closing of stomata takes place as a result of ______________. |
Active transport into and out of guard cells |
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Which 2 major compounds are involved in opening and closing of stomata? |
Starch, CO2 |
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During day, starch is converted into __________ in ___________ which in turn dissociates into _________. |
Malic acid, cytoplasm of guard cells, H+ and malate ions |
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H+ ions given out of cells and ___________ from ________ enter into guard cells. |
K+ ions, subsidiary cells |
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The intake of K+ ions is balanced by intake of _____. This raises __________ of guard cells. |
Cl- ions, osmotic pressure |
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Answer w.r.t. mechanism of opening and closing of stomata: At night photosynthetic activity ceases. What is the effect? (Minor level) |
CO2 concentration increases pH becomes acidic 5.0 |
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In presence of CO2, an inhibitor hormone _____________ functions and inhibits Uptake of K+ and Cl- ions by - |
Abscissic acid (ABA) 1.Changing diffusion 2. Changing permeability of guard cells |
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Who proposed Starch sugar hypothesis? It explains ____________. |
Steward, mechanism of opening and closing of stomata |
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Explain starch sugar hypothesis for opening of stomata |
Day - chloroplasts in guard cells - photosynthesis - sugar - OP increase - Endosmosis |
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Explain starch sugar hypothesis for closing of stomata |
Night - sugar to starch - increase TP - exosmosis |
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Mention the parts of stomatal apparatus with numbers |
1. 2 Guard cells 2. 1 Stoma 3. Many accessory or subsidiary cells |
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Guard cells are ______________. What is the speciality of these cells w.r.t. other cells of the tissue type? |
Modified Epidermal cells, presence if chloroplasts |
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Shape of guard cells |
Dicot - kidney shaped Monocot - Dumbbell shaped |
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How many nuclei do guard cells have? How is the cytoplasm? |
1, peripheral granular |
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Comment on walls of guard cells |
1. Inner - Thick, elastic 2. Outer - Thin, elastic, Permeable |
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Inner wall of guard cells is thick due to _____________. |
Presence of secondary wall layer |
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Opening of stoma is also aided due to _________________ of guard cells |
Radial orientation of cellulose microfibrils in cell walls |
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What is a stoma? |
Elliptical pore formed due to specific arrangement of guard cells |
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What are accessory cells? |
Cells immediately surrounding guard cells |
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____________ are reservoirs of K+ and Cl- ions. |
Accessory cells |
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Subsidiary cells are reservoirs of ___________. |
K+ and Cl- ions |
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Which gases are exchanged through stomata? |
CO2 and O2 (Note: not H2O because it is only diffused out - not involved in exchange) |
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Which gas only diffuses out through stoma? |
Water vapours |
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How much percent of water absorbed is utilized by plants? |
2% |
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Define transpiration |
Evaporative loss of water in form of water vapour by aerial parts of plants |
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Mention types of transpiration with percentage transpiration through each |
1. Cuticular - 8-10% 2. Lenticular - 0.1% 3. Stomatal - 80-90% |
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What is cuticle? |
Cuticle is waxy coating on epidermis of leaves |
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Thickness of cuticle varies from plant to plant - True or False |
True |
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Function of cuticle |
To Check transpiration |
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Actual cuticular transpiration takes place through _______ |
Cracks in cuticle or by diffusion through thin areas of cuticle |
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Factor affecting Rate of cuticular. Give one application |
It is inversely proportional to thickness of cuticle. In xerophytes, cuticle is thicker to decrease water loss |
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Lenticular respiration occurs in - |
Older bark Pericarp of woody fruits Pneumatophores |
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Give the types of leaves based on location of stomata |
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Stomata connect - |
Intercellular spaces between spongy tissues to atmosphere |
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Diffusion can account for only _____________ movement of molecules. |
Short distance |
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Movement of molecules across a typical plant cells (about _________) takes approximately ________. |
50 microns, 2.5 sec |
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Water, minerals and food are generally moved by ______________ system. |
Mass or bulk flow |
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What is mass flow? |
Mass flow is the movement of substances in bulk or en masse from one point to another as a result of pressure differences between the two points |
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What is characteristic of mass flow? |
Substances in solution or in suspension are swept along at same pace |
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Bulk flow can be achieved by ___________ or _________. |
Positive hydrostatic pressure, negative hydrostatic pressure |
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Give one example each of - Positive hydrostatic pressure, negative hydrostatic pressure |
1. Garden hose 2. Suction through straw |
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Define Translocation |
The bulk Movement of substances through the conducting or vascular tissues of plants is called Translocation |
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Colour of root hair |
Colourless |
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Layers of cell wall of root hair |
Outer pectin, inner cellulose (OPIC) |
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Pathway of water was given by ____________. |
E. Munch |
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According to E. Munch, what is the path of water? |
Soil - Epidermis - Cortex - Endodermis - Pericycle - Xylem |
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What are the main pathways of water? |
1. Apoplast 2. Symplast 3. Transmembrane |
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Apoplastic movement of water takes place through - |
Cell walls and intercellular spaces |
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____________ pathway does not involve crossing cell membrane. |
Apoplast |
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Choose correct option in each w.r.t. to apoplast - 1. Osmotic/ Non-osmotic 2. Dependent/ Independent of gradient 3. Due to absorption/ imbibition |
1. Non-Osmotic 2. Dependent 3. Imbibition |
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Apoplast is continuous movement throughout the transport - True or False giving reason |
False - Apoplast is continuous movement throughout the plant, except the casparian strips |
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Which pathway of water is faster and why? |
Apoplast - because it provides no barrier to water movement |
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Xylem and phloem are parts of _____________ pathway. Why? |
Apoplast - they are non living conduits |
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What is symplastic pathway? |
Symplastic system is the system of interconnected protoplast through plasmodesmata |
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What is symplast? |
Neighbouring cells are connected through cytoplasmic strands that extend through plasmodesmata and form cytoplasmic network call symplast. |
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Symplastic movement is aided by ______________. |
Cytoplasmic streaming |
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Which layer of root cells is impervious to water and why? |
Endodermis. - band of suberised matrix called casparian strips |
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Movement of water through root layers is ultimately ___________ in __________. |
Symplastic, endodermis |
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Transmembrane pathway of water is through ____________. |
All layers of cell (including tonoplast) |
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How are mycorrhiza useful for plants in absorption of water? |
Very large surface are |
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Give example of obligate association of plant with mycorrhiza |
Pinus seeds cannot germinate without mycorrhiza |
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Factors affecting water absorption |
1. Availability of soil water 2. Concentration of soil solution 3. Soil aeration 4. Soil temperature 5. Osmotic pressure of root hair 6. Root anatomy 7. Transpiration |
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How does availability of soil water affect absorption? |
Decrease in soil water below the permanent wilting percentage causes considerable decrease in absorption of water. |
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How does concentration of soil solution affect absorption? |
Increased concentration of soil due to presence of salts inhibits |
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What is physiologically dry soil? |
Soil in which water is concentrated. Having high osmotic pressure. Here water is physically present, but not available for absorption |
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How does soil aeration affect absorption? |
Low O2 and high CO2 retards growth and disturbs metabolism. Retards rate of absorption |
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Optimum range of soil temperature is ______________ for maximum water absorption. |
20℃ to 30℃ |
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How does osmotic pressure of root hair affect absorption? |
More OP more rate of absorption |
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How does root anatomy affect absorption? |
Less root hair, thick walled cortical cells, casparian strips reduce rate of absorption |
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How does transpiration affect absorption? |
High rate of transpiration more absorption rate |
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What are the two theories explaining why root cells are hypertonic? |
1. Active Osmotic Theory 2. Passive Transpiration Theory (AOPT) |
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According to active Osmotic Theory, root hair and cortical cells are hypertonic due to - |
Metabolic activities in the living cells of root utility ATP |
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In active osmotic theory, after absorption water is transported to next cells due to __________. |
DPD |
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According to active Osmotic Theory, root cells alternately become _______________. |
Flaccid and turgid |
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According to passive transpiration theory, what is major factor for absorption of water? |
Suction or cohesive pull developed by the leaves due to transpiration develops water deficit and draws water from the petiole which pulls water from the stem |
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According to which theory of absorption, metabolic energy is not used? |
Passive transpiration theory |
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Role of root in absorption according to passive transpiration theory |
Only ad physical absorbing organ providing surface area for absorption |
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Role of root in absorption according to passive transpiration theory |
Only ad physical absorbing organ providing surface area for absorption |
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One atmospheric pressure raises a column of water up to _______ m or ______ feet |
10.3 m, 34 feet |
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Height of 1. Californian Sequoia plant 2. Australian Eucalyptus plant |
1. 111.6 m or 366.2 feet 2. 114.4 m or 374 feet |
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In a well watered potted tomato plant, cut the stem close to root. What will you observe? |
Exudation/ bleeding of xylem sap from stump |
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How can we measure the rate of exudation from cut stump? What else can be determined? |
Fix a rubber tube to cut stem as a sleeve and collect, composition of exudates |
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Root pressure is a (positive/ negative) pressure, responsible for - |
Positive, pushing up water to small heights in stem |
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Who explained Root pressure? |
Priestly |
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What was Priestly's explanation of root pressure? |
Priestly explained that a sort of hydrostatic pressure develops in the root due to accumulation of absorbed water |
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What is guttation? |
Water loss in its Liquid phase through intact plant parts is known as guttation |
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Guttation is observed in - |
Grass blades, fern leaflets, leaves of many herbaceous plants |
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Excess water in tips of Grass blades, fern leaflets, leaves of many herbaceous plants etc collects in form of ____________ around special openings called _____________ of __________. |
Droplets, hydathodes, veins |
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Exuded water from guttation often contains __________. What is the further consequence? |
Calcium salts, water evaporates off, white crust remains on surface |
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Hydathodes are also known as ___________. |
Chalk glands |
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2 facts confirming root pressure: |
1. Living cells are essential in the root for root pressure to develop 2. Oxygen supply effects root pressure |
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What is magnitude of root pressure? |
Less than 2 atm |
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How is root pressure measured? |
By manometer sealed over cut stump |
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Root pressure is sufficient only for ____________. |
Herbs and shrubs |
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Root pressure is not applicable to plants taller than __________ |
20 m or 68 feet |
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Comment on root pressure in tall connifers and other gymnosperms |
Absent |
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Root pressure is absent in _________. |
Tallest plants like conifers and other gymnosperms |
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Season dependence of root pressure. So Why root root pressure is not applicable? |
During summer root pressure is lowest when transpiration rate is very high, wheras during spring it is highest when transpiration rate is low. Actually in summer aerial parts of plants need maximum water |
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What cannot be explained by root pressure theory? |
Root pressure theory cannot explain ascent of sap through xylem elements which is dead lignified tissue |
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Capillarity theory is a (physical/ living) theory |
Physical |
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Who gave Capillarity theory? |
Boehm |
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According to Boehm water rises in narrow tube by - |
Capillarity develop because of force of surface tension just as oil rises in the wick of an oil lamp |
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According to Capillarity theory, water continues to rise until - |
Forces of Adhesion and cohesion are balanced by downward force of gravity |
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In a 1 micron Capillary, water rises to a height of ___________, only due to ____________. |
29 m, resistance to flow of water |
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Demerits of Capillarity theory |
1. Distance to which water can rise is limited 2. Tube must be open, hollow and open at both ends. In gymnosperms and pteridophytes, xylem is vessel less and tracheids have cross walls at ends 3. Requires free surface, but xylem not in direct contact with water 4. Requires uniform diameter, but not so in xylem 5. Thinner capillary, more rise distance. Opposite in xylem. |
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Who proposed cohesion theory? |
Dixon and Jolly |
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Magnitude of cohesive force of water ___________ |
350 atms |
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Cell with shrunken protoplasm is called ____________. |
Plasmolysed cell |
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Water is first lost from ___________ and then from __________. |
Cytoplasm, vacuole |
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When Plasmolysed cell is placed in hypotonic solution, it reabsorbs by _______________, its protoplast resumes original shape. This is known as ___________. |
Endosmosis, deplasmolysis |
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What is osmotic pressure? |
Pressure applied to stop osmosis or the pressure needed to prevent passage of pure water through semi-permeable membrane |
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OP is proportional to - |
Solute molecules in given amount of solvent |
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Compare OP of hypertonic and hypotonic solution |
OP of Hypertonic more than OP of hypotonic |
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Give relationship between osmotic pressure and osmotic potential |
Numerically equal, opposite in sign. Osmotic pressure is positive pressure applied, osmotic potential is negative |
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Give alternate name and symbol for osmotic potential |
Solute potential - Psi(s) |
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Define turgor pressure |
The hydrostatic pressure that develops due to endosmosis inside plant cell |
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Define pressure potential |
The pressure exerted by protoplasts due to entry of water against rigid walls |
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______________ is ultimately responsible for enlargement and extension growth of cells |
Turgor pressure |
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After endosmosis, why doesn't cell rupture? |
Rigidity of cell wall |
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What is wall pressure? |
Protoplasts exert pressure potential on wall. Cell wall is rigid and develops an equal and opposite pressure on cell contents known as WP |
|
Relate TP, WP and OP |
In fully turgid cell, TP=WP=OP |
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Give full form of DPD, along with alternate names and abbreviations |
Diffusion pressure deficit Suction force (SF) Suction pressure (SP) |
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What is DPD? |
Difference between DP of pure water (1236) and that of solution |
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DPD is proportional to |
Solute |
|
Give formulae of DPD |
DPD = DP (pure water : 1236) - DP (solution) = OP - TP (WP) |
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DPD in a fully turgid cell is _______ |
Zero |
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When DPD =0, what happens? |
Endosmosis stops |
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Water potential is denoted by _______ and is measured in _______. |
Psi(w), pressure units like pascals |
|
Pressure potential is denoted by |
Psi (p) |
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What is value of water potential at atmospheric pressure? |
Psi(w)=Psi(s) |
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What is water potential? |
Chemical potential of water or potential energy of water |
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Water potential is proportional to |
Solvent |
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Give formalae for water potential |
Psi(w) = Psi (s) + Psi(p) = - OP + TP = - DPD |
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Define solute potential |
Magnitude of lowering of water potential due to dissolution of solute is called solute potential |
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If pressure greater than atmospheric pressure is applied to solution, it's water potential (increases/decreases) |
Increases |
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State whether positive or negative: 1. Pressure potential 2. Solute potential |
1. Usually positive 2. Always negative |
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Comment on movement of water w.r.t. to following: 1. Concentration 2. OP 3. Psi(s) 4. DPD 5. Psi(w) |
1. Po to per 2. Less to more 3. More to less (less negative to more negative) 4. Less to more 5. More to less (less negative to more negative) |
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Which are the first and second physical processes to occur? |
Imbibition and Diffusion respectively |
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What is imbibition? |
Adsorption of water by hydrophilic compounds |
|
What happens in Adsorption? |
Water gets tightly adsorbed on surface of compounds without forming a solution. So, compounds show swelling |
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Meaning of imbibant and imbibant |
1. Imbibant - substance/solid/colloid which adsorbs water 2. Imbibate - adsorbed liquid |
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What is heat of wetting? |
Water molecule get highly adsorbed and become immobilized and lose most of kinetic energy in form of heat |
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After imbibition, imbibant increases in ___________. |
Volume |
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Pre-requisites for imbibition |
1. Water potential gradient 2. Affinity Between imbibant and liquid |
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Examples of imbibants |
Proteins, cellulose, pectic compounds, starch, gum, dry seeds |
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Why is glucose converted into Sucrose for transportation? |
Sucrose is osmotically active |
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Give following values for pure water and mention whether maximum or minimum 1. DP 2. OP 3. DPD 4. Psi (w) |
1. 1236 (Max) 2. 0 (Min) 3. 0 (Min) 4. 0 (Max) |
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Give stages of plasmolysis with description |
1. Limiting - Normal Cell 2. Incipient - Protoplasm withdraws from corners 3. Evident/ Existing/ Obvious - Complete detachment from cell membrane (LIE) |
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Magnitude of ___________ of water is 350 atms |
Cohesive force |
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Water has great cohesive force due to ___________. |
Hydrogen bonds |
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Cohesive and adhesive properties developed form ____________ in xylem. |
Unbroken continuous water column |
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How is a continuous column of water maintained in xylem? |
Xylem vessels are short,wide and without end walls. They are placed one above the other and form a tubular structure which extends from the root to the top of the plant. OR Adhesive and cohesive forces, continuous anastomizing network of xylem elements |
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Transpiration pull develop a (positive/negative) pressure or ___________ of about ______ atm in xylem sap. |
Negative, tension, 20 |
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H-bond is very (weak/strong). |
Weak |
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Although, H-bond is very weak, how does is account for strong cohesion? |
When present in large numbers as in water, a very strong mutual cohesive force is developed |
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According to cohesion theory, what causes pulling force for water? |
Water lost from mesophyll due to transpiration - increase OP - tension - pulling force |
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What is the supposed demerit of cohesive theory? |
Due to variations in temperature/ atmospheric pressure, air bubbles may break continuity of water column |
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How do xylem vessels allow collateral flow? |
Tracheids and vessels are pitted. These pits connect adjacent cells with one another and allow collateral water flow |
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Who showed that under normal conditions, no air bubbles are present in xylem even in last stage of wilting? |
Renner and Bode |
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What was Renner and Bode's observation? |
Under normal conditions, no air bubbles are present in xylem even in last stage of wilting |