Photophosphorylation & Chemiosmosis
Photophosphorylation/ Chemiosmosis. (Peter Mitchell 1961) The production of ATP in the chloroplast or in other membranes during light reaction is called photophosphorylation. Photophosphorylation occurs in ATP-synthase complex or coupling factor (CF) located in stroma thylakoid membranes. The coupling factor is also responsible for transport of H+ from the thylakoid channel to the stroma. The electron […]
Light Dependent Reaction-Z scheme
Electron transport actually begins with the arrival of excitation energy at the photosystem II reaction center chlorophyll, P680, which is located near the lumenal side of the reaction center. As a consequence of this initial endergonic excitation process, P680* can rapidly (within picoseconds, 10−12 s) transfer electrons exergonically to pheophytin(Pheo). Pheophytin considered the primary electron […]
Emerson Enhancement Effect
By the late 1950s, several experiments were puzzling the scientists who studied photosynthesis. One of these experiments carried out by Emerson, measured the quantum yield of photosynthesis as a function of wavelength and revealed an effect known as the red drop. If the quantum yield is measured for the wavelengths at which chlorophyll absorbs light, […]
Light and Photosynthesis
Light is the visible portion of spectrum. Light Has Characteristics of Both a Particle and a Wave A wave is characterized by a wavelength, denoted by the Greek letter lambda ( ƛ ), which is the distance between successive wave crests. The frequency, represented by the Greek letter nu ( v ), is […]
LEAVES ARE PHOTOSYNTHETIC MACHINES
The leaves are modified for maximum absorption of light. Anatomy of leaf Epidermis: The leaf is sheathed with upper and lower epidermis. The exposed surfaces of the epidermal cells are coated with a cuticle. Mesophyll The photosynthetic tissues are located between the two epidermal layers and are consequently identified as mesophyll (meso,middle; phyll,leaf) tissues. Palisade […]
Photosynthesis; Introduction
Photosynthesis is the fundamental basis of competitive success in green plants and the principal organ of photosynthesis in higher plants is the leaf. It is the process in which plants utilize carbon dioxide and water as raw material in the presence of light and chlorophyll convert them into glucose (carbohydrates) and release oxygen as a […]
PHOTORECEPTORS ABSORB LIGHT
Photoreceptors are defined as pigment molecules that process the energy and informational content of light into a form that can be used by the plant. A pigment that contains protein as an integral part of the molecule is known as a chromoprotein. Thus, photoreceptors typically are chromoproteins. The chromophore (Gr. phoros, bearing) is that portion […]
COHESION TENSION THEORY
This theory was proposed by Dixon according to this theory a number of forces responsible for upward movement of sap in plants. The most widely accepted theory for movement of water through plants is known as the cohesion theory. Transpiration Pull What is the driving force? According to the cohesion-tension theory, the driving force for […]
TRANSPIRATION
Loss of water in the form of vapours from plant surface. The loss of water due to transpiration is quite high. Rather 98-99% of the water absorbed by a plant is lost in transpiration. Hardly 0.2% is used in photosynthesis while the remaining is retained in the plant during growth. TRANSPIRATION IS DRIVEN BY DIFFERENCES […]
Water loss from Leaf
After water has evaporated from the cell surface into the intercellular air space, diffusion is the primary means of any further movement of the water out of the leaf. The waxy cuticle that covers the leaf surface is a very effective barrier to water movement. It has been estimated that only about 5% of the […]