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2023 Solved Old Paper (BOT - 204)

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SEE ANSWER  https://mscbotanysemiimgsubikaner.blogspot.com/2024/06/osmotic-potential.html SEE ANSWER  https://mscbotanysemiimgsubikaner.blogspot.com/2024/06/transpiration-is-necessary-evil.html SEE ANSWER  https://mscbotanysemiimgsubikaner.blogspot.com/2024/06/donnan-equilibrium.html SEE ANSWER  https://mscbotanysemiimgsubikaner.blogspot.com/2024/06/salt-respiration.html SEE ANSWER  https://mscbotanysemiimgsubikaner.blogspot.com/2024/06/four-non-leguminous-nitrogen-fixing.html SEE ANSWER  https://mscbotanysemiimgsubikaner.blogspot.com/2024/06/hup-genes.html SEE ANSWER  https://mscbotanysemiimgsubikaner.blogspot.com/2024/06/apical-dominance.html SEE ANSWER  https://mscbotanysemiimgsubikaner.blogspot.com/2024/06/foolish-seedling-disease.html SEE ANSWER  https://mscbotanysemiimgsubikaner.blogspot.com/2024/06/four-day-neutral-plants.html SEE ANSWER  https://mscbotanysemiimgsubikaner.blogspot.com/2024/06/senescence.html SEE ANSWER  https...

Essay on Abscisic Acid

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Abscisic Acid (ABA):- > It is found in older leaves, apical buds and seeds. > Both GA and ABA hormones work opposite to each other. > ABA inhibits the biosynthesis of the hormone GA. 1. Discovery of Abscisic Acid:- - Torsten Hemberg (1940) reported that dormant potato tubers and buds of ash (Fraxinus excelsior) contained inhibitor (rather than stimulators) that blocked the effects of IAA. When the buds germinated, the amount of these inhibitors decreased.  - Eagles and Wareing (1963) isolated an inhibitor from the birch (Betula pubescens) leaves held under short day conditions. When this substance was reapplied to the leaves of birch seedlings, apical growth was completely arrested. As this substance induced dormancy, they named it as ‘dormin’.  - Cornus and Addicot (1963) isolated this compound from the shedding bolls of cotton plant. - Ohkum (1965) isolated an inhibitor from cotton fruits and named it ‘abscisin II’.  - Cornforth (1965) demonstrated that both Do...

Active Uptake of Minerals

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Active Absorption (Active Uptake) :- Ø   It has often been observed that the cell sap in plants accumulates large quantities of min­eral salts ions against the concentration gradient. It  is an active process which involves the expenditure of metabolic energy through respiration. Ø   Following evidences favor this view:- i.  The factors like low temp., deficiency of O 2 , metabolic inhibitors etc. which inhibit metabolic activities like respiration in plants also inhibit accumulation of ions. ii.  Rate of respiration is increased when a plant is transferred from water to salt solution. It is called salt respiration. a. The Carrier Concept:-  According to this theory the plasma membrane is impermeable to free ions. But some compounds present in it acts as carrier and combines with ions to form carrier-ion-complex which can move across the membrane. On the inner surface of the membrane this complex breaks releasing ions into the cell while the carrier go...

Two Theories of Mechanism of Stomatal Movement

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Mechanism of Stomatal Movement:- > Stomata function as turgor-operated valves because their opening and closing movement is governed by turgor changes of the guard cells.  > Whenever, the guard cells swell up due to increased turgor, a pore is created between them. With the loss of turgor the stomatal pores are closed. > Stomata generally open during the day and close during the night with a few exceptions. >The important factors which govern the stomatal opening are light, high pH or reduced CO2 and availability of water. The opposite factors govern stomatal closure, viz., darkness, low pH or high CO2 and dehydration. > There are three main theories about the mechanism of stomatal movements: 1. Classical Starch Hydrolysis Theory:- - The main features of the theory were spelled out by Sayre (1923).  - It was modified by Steward (1964).  - The guard cells contain starch.  - At low carbon dioxide concentration (in the morning achieved through photosynthe...