Diverging temperature responses of CO2 assimilation and plant development explain the overall effect of temperature on biomass accumulation in wheat leaves and grains.

Nicholas C Collins,Boris Parent

doi:10.1093/aobpla/plw092

Abstract

There is a growing consensus in the literature that rising temperatures influence the rate of biomass accumulation by shortening the development of plant organs and the whole plant and by altering rates of respiration and photosynthesis. A model describing the net effects of these processes on biomass would be useful, but would need to reconcile reported differences in the effects of night and day temperature on plant productivity. In this study, the working hypothesis was that the temperature responses of CO2 assimilation and plant development rates were divergent, and that their net effects could explain observed differences in biomass accumulation. In wheat (Triticum aestivum) plants, we followed the temperature responses of photosynthesis, respiration and leaf elongation, and confirmed that their responses diverged. We measured the amount of carbon assimilated per "unit of plant development" in each scenario and compared it to the biomass that accumulated in growing leaves and grains. Our results suggested that, up to a temperature optimum, the rate of any developmental process increased with temperature more rapidly than that of CO2 assimilation and that this discrepancy, summarised by the CO2 assimilation rate per unit of plant development, could explain the observed reductions in biomass accumulation in plant organs under high temperatures. The model described the effects of night and day temperature equally well, and offers a simple framework for describing the effects of temperature on plant growth.

Highlights

High temperatures decrease biomass accumulation in plant leaves (Vile et al 2012), cereal grains (Wheeler et al 1996) and whole plants, with implications for agricultural productivity and ecology under a climate change scenario (Peng et al 2004)
Up to a temperature optimum, the rate of any developmental process increased with temperature more rapidly than that of CO2 assimilation and that this discrepancy, summarised by the CO2 assimilation rate per unit of plant development, could explain the observed reductions in biomass accumulation in plant organs under high temperatures
The temperature response curves of net day photosynthesis (PN) and dark respiration (R) were both adequately described by this equation (Fig.1b, n > 4, R2 = 0.99 and 0.97, respectively)

Summary

Introduction

High temperatures decrease biomass accumulation in plant leaves (Vile et al 2012), cereal grains (Wheeler et al 1996) and whole plants, with implications for agricultural productivity and ecology under a climate change scenario (Peng et al 2004). An emerging consensus is that carbon balance is a critical factor in responses of biomass accumulation processes to temperature changes This view comes from studying temperature responses of grain dry mass (Wardlaw 1994; Wheeler et al 1996), and leaf dry mass per area (LMA) or its reciprocal, the specific leaf area (Poorter et al 2009). High temperatures accelerate cell expansion and division, and hasten genetic programs of organ differentiation, shortening the period over which biomass can accumulate (Parent et al 2010b). These effects are largely independent of variations in carbon fixation (Morita et al, 2005)

Methods

Results

Discussion

Conclusion