ON THE DEVELOPMENTAL DEPENDENCE OF LEAF ESPIRATION:RESPONSES TO SHORT- AND LONG-TERM CHANGES IN GROWTH TEMPERATURE

Abstract

Using measurements of leaf respiratory O2 uptake (R), we investigated whether immature and mature Arabidopsis thaliana (ecotype Columbia) leaves differed in their response to temperature. Confocal microscopy (using plants with mitochondrially targeted green fluorescent protein [GFP]) was used to determine whether ontogenetic changes in R are associated with concomitant changes in mitochondrial morphology/abundance. Comparisons were made of warm-grown (25/20°C) leaves, warm-grown leaves shifted to cold (5°C) for 10 days, and cold-developed leaves. Short-term Q10 values and the ability to cold-acclimate were determined. In warm-grown plants, rates of R per mass were highest in immature leaves, decreasing as leaves developed. Moreover, although mitochondrial size (5.6-6.5 μm3) remained constant during development, mitochondrial number per μm3 declined from 0.01 to 0.003 as leaves expanded (i.e., mitochondrial density decreased). Immature and mature leaves did not differ in Q10 values but did differ in their ability to cold-acclimate. Whereas mature leaves had clear evidence of cold acclimation (e.g., when measured at 25°C, R was highest in cold-developed leaves), young leaves had none. Collectively, the results highlight the changes in rates of R, mitochondrial density, and biomass allocation associated with leaf development and that changes in respiratory flux associated with acclimation only take place within mature tissues. Show more