Which of the following statements is the most likely explanation for plant withering due to leaky membranes in cold temperatures? A. Too many H+ ions accumulate inside the thylakoid, so ATP synthase makes too little ATP.
B. Too many H+ ions accumulate inside the thylakoid, so ATP synthase makes too much ATP.
C. H+ ions do not accumulate inside the thylakoid, so ATP synthase makes too little ATP.
D. H+ ions do not accumulate inside the thylakoid, so ATP synthase makes too much ATP.

C. H+ ions do not accumulate inside the thylakoid, so ATP synthase makes too little ATP.

Explanation:

Plant withering refers to the virtual death of plant cells due to lack of food. During the light-dependent reactions of photosynthesis, ATP needed for the synthesis of sugar (food) is created in the thylakoid membrane of the CHLOROPLAST of plant cells.

In the light-dependent reaction, hydrogen ions (H+) builds up/accumulate in the thylakoid lumen to create an electrochemical or proton gradient i.e. a difference in the concentration of H+ ions across the membrane. The hydrogen ions passes through a protein complex called ATP synthase, which forms ATP from ADP (by adding phosphate group), from the energy generated by the electrochemical gradient formed as a result of hydrogen in (H+) build up.

Hence, a plant that possess leaky membrane due to the cold temperature will likely wither because H+ ions are not able to accumulate inside the thylakoid causing a proton gradient, so ATP synthase makes too little ATP.