Effect of carbohydrates and night temperature on night respiration in rice uri icon

abstract

  • Global warming causes night temperature (NT) to increase faster than day temperature in the tropics. According to crop growth models, respiration incurs a loss of 40-60% of photosynthate. The thermal sensitivity of night respiration (R-n) will thus reduce biomass. Instantaneous and acclimated effects of NT on R-n of leaves and seedlings of two rice cultivars having a variable level of carbohydrates, induced by exposure to different light intensity on the previous day, were investigated. Experiments were conducted in a greenhouse and growth chambers, with R-n measured on the youngest fully expanded leaves or whole seedlings. Dry weight-based R-n was 2.6-fold greater for seedlings than for leaves. Leaf R-n was linearly related to starch (positive intercept) and soluble sugar concentration (zero intercept). Increased NT caused higher R-n at a given carbohydrate concentration. The change of R-n at NT increasing from 21 degrees C to 31 degrees C was 2.4-fold for the instantaneous response but 1.2- to 1.7-fold after acclimation. The maintenance component of R-n (R-m'), estimated by assimilate starvation, averaged 28% in seedlings and 34% in leaves, with no significant thermal effect on this ratio. The acclimated effect of increased NT on R-m' across experiments was 1.5-fold for a 10 degrees C increase in NT. No cultivar differences were observed in R-n or R-m' responses. The results suggest that the commonly used Q10=2 rule overestimates thermal response of respiration, and R-n largely depends on assimilate resources.

publication date

  • 2015
  • 2015
  • 2015