Some Important Facts on Physiology and Biochemistry

DPD can become zero (fully turgid cell). TP can also become zero (flaccid cell) but O.P. of a cell can never be zero.

Cryoscopic osmometer:

Measures osmotic potential of solution by measuring its freezing point.

Tensiometer:

Instrument for measuring soil water tension.

Psychorometer:

To mearene relative humidity as well as transpiration.

Manometer:

To measure pressure like root pressure.

Barometer:

To measure atmospheric pressure.

Porometer (F. Dawin, 1912):

To measure the size of stomata.

Potometer:

To measure the rate of transpiration.

Atmometer:

To measure pull caused by evaporation of water from a porous pot.

Term guttation was coined by Bergerstein (1887).

COCl₂ Paper Method (Hygrometric method, Stahl, 1894)-Used to compare the rates of transpiration.

Blue light of visible light promotes stomatal opening.

Plants growing at high altitudes exhibit xeromorphy i.e., adaptation to minimise transpiration.

Transpiration ratio:

The amount of water lost per unit of dry matter produced during the growing season of a plant.

Stomatal frequency:

Number of stomata per unit area of leaf its value is 1000 – 60,000/ cm² or 10 – 600/mm².

Permanent wilting coefficient (PWP or PWC):

Amount of soil water at which the plants growing in it show first signs of permanent wilting.

Antitranspirants:

Chemicals which have been found to reduce the rate of transpiration without affecting CO₂ uptake. They may be metabolic inhibitors (e.g., ABA-Abscissic acid, PMA – Phenyl mercuric acetate and Aspirin) or film forming anti-transpirants (e.g., silicon emulsions and some low viscosity waxes).

Selectively or differentially permeable membrane:

Membrane which is normally semipermeable but allows selective transport of certain solutes.

SPAC (Soil Plant Atmosphere Continuum):

Plants function as living connecting system between soil water and*atmospheric water.

Stephen Hales (1676 -1761)-Father of Plant Physiology, coined the term root pressure.

Yon Mohl:

Gave diagrammatic representation of size of stoma at different times of the day.

Transpiration flux: The quantity of water transpired by a unit area of leaf surface in a unit time.

Pfeffer:

Proposed term ‘osmotic pressure’. Nollet : Coined term “osmosis”.

TP = 0 in plasmolysed cell.

Deplasmolysis:

A plasmolysed cell regains normal condition if placed in a hypotonic solution.

Slatyer and Taylor:

Proposed concept of water potential.

Cohesive force of attraction between water molecules is upto 300 bars.

In Saxifraga-Rate of guttation is high during flowering.

Active hydathode lack cuticle over specialized cells.

Lactuca scariola and Sylphium laciniatum are called compass plants as their leaves lie vertically in north-south direction.

In Colocasia antiquorum, guttation is a normal process.

Transpiration is old stems and fruits take place through lenticels.

Osmotic pressure can be calculated by following relationship OP = cRT (where c = molar concentration of solution, R is gas constant and T is absolute temperature -273°C).

Root pressure is absent in Gymnosperms.

When the transpiration pull is exerted, a negative pressure or tension is generated in the xylem.

Isotonic solution:

Solution which has concentraton similar to that of cell sap.

Steward (1964):

Proposed starch sugar hypothesis.