Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/20/2007
Publication Date: 9/1/2007
Citation: Ristic, Z., Bukovnik, U., Prasad, V. 2007. Correlation between heat stability of thylakoid membranes and loss of chlorophyll in winter wheat under heat stress. Crop Science. 47:2067-2073. Interpretive Summary: Determination of mechanisms associated with heat tolerance and identification of screening methods is crucial for improvement of heat tolerance in crop plants. New, inexpensive and easy-to-use methods must be developed for high throughput screening for heat tolerance in wheat and other crops. We investigated the relationship between heat tolerance and loss of chlorophyll in winter wheat under heat stress conditions, and tested the possibility of using chlorophyll loss, as determined by SPAD chlorophyll meter, as an indicator of heat tolerance in wheat. A strong negative linear correlation between heat tolerance and chlorophyll content was observed. Loss of chlorophyll under heat stress, as determined with a SPAD chlorophyll meter, could be used as a reliable and high throughput method for screening for heat tolerance in wheat. The results of this study could aid in screening and producing new wheat cultivars with improved tolerance to heat stress.
Technical Abstract: The objectives of this study were to (1) investigate the relationship between the heat stability of thylakoid membranes/PS II and loss of chlorophyll in winter wheat under heat stress conditions, and (2) to test the possibility of using chlorophyll loss, as determined by SPAD chlorophyll meter, as an indicator of heat tolerance in wheat. We assessed heat tolerance by examining the heat stability of thylakoid membranes using a fluorescence meter and measured chlorophyll content using SPAD chlorophyll meter in mature plants (at flowering stage) of twelve cultivars of winter wheat experiencing 16-d-long heat stress. Heat stress caused damage to thylakoid membranes in all wheat cultivars as indicated by the increases in the ratio of constant fluorescence (O) and the peak of variable fluorescence (P). Heat stress also caused a progressive decline in chlorophyll content in most cultivars. A strong negative linear correlation between heat-induced increases in O/P ratio of chlorophyll a fluorescence (thylakoid membranes/PS II damage) and chlorophyll content was observed (e.g. R2 = 0.79, n = 60). The results suggest that heat-induced damage to thylakoid membranes and chlorophyll loss are closely associated and that chlorophyll retention under heat stress conditions could indicate heat tolerance. Measurements of chlorophyll content with a SPAD chlorophyll meter could be used as a method for high throughput screening for heat tolerance in wheat.