The role of ABA signaling during water stress in the guard cells in presence and absence of ABA;

a) Anion effl¬ux leads to depolarization of the plasma membrane, which drives K+ effl¬ux. The eff¬lux of ions (A– and K+) reduces the turgor pressure of guard cells, resulting in stomatal closure.

b) Both OST1 and CPKs phosphorylate and thereby activate plasma membrane anion channels, leading to ef¬flux of anions (A–). But  this process can be inhibited directly by PP2Cs 

c) Inhibition of PP2C activity releases the positive regulator kinase OST1 from inhibition, resulting in both phosphorylation and activation of NADPH oxidases (RBOHs)

d) RBOHs catalyze the formation of apoplastic reactive oxygen species (ROS),  which triggers opening of plasma membrane Ca2+-permeable ion channels 

e) The resulting elevation of cytosolic Ca2+ leads to activation of calcium-dependent protein kinases (CPKs), which can also activates the RBOH proteins further promoting Ca2+ infl¬ux into the cytosol.

Which statements belongs to the presence and absence of ABA during signalling;

I. In presence of  ABA

II. In absence of ABA

Which of the following combination from the given above statements is correct?

#Question id: 10472

#Unit 6. System Physiology – Plant

In greenhouse grown leaves of broad bean stomatal movements closely correlate with incident solar radiation at the leaf surface and stomatal aperture  opening and closing as light levels reaching the leaf surface given in graph

A. Mid of the day stomatal aperture has a largest diameter, water loss and transpiration rate will be highest at the  same time

B. In mid of the day incident light is highest in terms of PPFD and can also say CO2 diffusion will be highest

C. The stomatal aperture has a largest diameter resulting closing of stomatal pore, water loss and transpiration rate will be lowest due to closing of stomata

D. In mid of the day incident light is highest in terms of PPFD resulting CO2 will not diffuse

which of the following combination from the given graph will be CORRECT?

#Question id: 10482

#Unit 6. System Physiology – Plant

A herbicides dichlorophenyldimethylurea (DCMU) is known as diuron an inhibitor of photosynthetic electron transport. Which one of the following option would be correct about diuron?

a.) Blocks electron flow at the plastoquinone acceptors of PSII by competing for the binding site of plastoquinone

b.) causes a partial inhibition of stomatal closing

c.) accepts electrons from the early acceptors of PSI such as A0 and then reacts with oxygen to form superoxide, O2 –

d.) causes a partial inhibition of light-stimulated stomatal opening

#Question id: 10483

#Unit 6. System Physiology – Plant

Given below some facts regarding the stomal responses in light condition. Which one of the following would be INCORRECT?

#Question id: 10484

#Unit 6. System Physiology – Plant

Blue light mediated activation of proton pumps which is electrogenic in nature can be measured or analyze by using which system?

#Question id: 10485

#Unit 6. System Physiology – Plant

What is the role of blue light in terms of stomatal study?

a.) Blue light activates a proton-pumping ATPase in the guard cell plasma membrane and leading to stomatal opening

b.) blue-light stimulation lowers the pH of the apoplastic space surrounding the guard cells, and generates the driving force needed for ion uptake and stomatal opening

c.) The sensitivity of guard cells to blue light increases as a function of their zeaxanthin concentration

d.) npq1 mutant opens at higher fluence rates of blue light, whereas the phot1/phot2 mutant fails to show any blue light–stimulated opening

Which one of the following combination is correct?

#Question id: 10486

#Unit 6. System Physiology – Plant

A patch clamp study shows a guard cell protoplast treated in the dark with the fungal toxin fusicoccin which is a well-characterized,