Chloroplast Structure after Water Shortage and High Temperature in Two Lines of Zea mays L. that Differ in Drought Resistance

Chloroplast structure in mesophyll cells from more xeromorphic drought-resistant (Polj 17) and less xeromorphic drought-sensitive (F-2) lines of Zea mays L. was studied in response to water stress and a combination of water and high-temperature stress. In the drought-resistant line water stress partly affected chloroplast structure; membranes of the chloroplast envelope were disrupted only in some chloroplasts, but grana were well preserved. Water stress and high-temperature stress affected chloroplasts to a greater extent but did not severely alter their structure. Grana were still visible, and only in some chloroplasts were they less distinguishable. Water shortage in the drought-sensitive line caused swelling of thylakoids and disappearance of outer membranes of the chloroplast envelope in many chloroplasts. Addition of temperature stress increased chloroplast disruption. The most striking difference was in the structural characteristics of chloroplasts after rehydration. Chloroplasts from the drought-resistant line appeared close to normal. In contrast, chloroplasts from the drought-sensitive line showed signs of additional deterioration in their structure. Differences in chloroplast structure under stress conditions between lines were likely the result of intraspecific differences in leaf dehydration, and possibly the result of intraspecific differences in the sensitivity of chloroplast membranes to high temperature.