Chloroplast Structure after Water and High-Temperature Stress in Two Lines of Maize that Differ in Endogenous Levels of Abscisic Acid

Abstract

Chloroplast structure in mesophyll cells from the high-level abscisic acid (ABA) line of maize (Zea mays L.), ZPBL 1304, and the low-level ABA line, ZPL 389, was studied in response to leaf dehydration and high temperature (45 C). Thirteen-day-old seedlings were exposed to 7-d soil drying followed by either 6-h or 24-h heat stress. Seven-day soil drying followed by 6-h high-temperature stress did not affect chloroplasts in line ZPBL 1304 but damaged many chloroplasts of line ZPL 389; chloroplast-envelope membranes were broken and not distinct, and many thylakoids were swollen. Seven-day soil drying followed by 24-h heat stress affected chloroplasts in both lines, but changes in chloroplast structure were greater in ZPL 389 than in ZPBL 1304. The main damage to the chloroplasts in ZPBL 1304 included thylakoid swelling, disruption of the chloroplast envelope, and distortion of chloroplast shape. Chloroplasts in ZPL 389 suffered severe damage: their shape was irregular, envelope membranes were not visible, g...