Leucine uptake by tomato leaf tissue under low temperature: Preincubation dependence of uptake reduction

Abstract

The uptake of 3H‐leucine by leaf fragments of Lycopersicon esculentum Mill. cv. Rutgers and L. hirsutum Humb. & Bonpl., a wild tomato, was studied. Two altitudinal races of L. hirsutum were used which differed in chilling tolerance. The temperature dependence of uptake was initially similar for all plant varieties. However, at temperatures below about 11°C, uptake progressively decreased in the more chilling‐sensitive varieties (L. esculentum, Low‐altitude L. hirsutum), but not in the more chilling‐tolerant (high‐altitude L. hirsutum) with increasing preincubation time. More than 60 min preincubation was required for this effect, and it was greatest at the lower temperatures. When leaf fragments, chilled for short periods of time (>22 h), were returned to 22°C, initial rates of uptake were recovered within 2 h. The relationship between membrane lipid changes and membrane protein activity under chill stress is discussed.