Respiratory energy demand for protein turnover and ion transport in wheat leaves upon water deficit

Abstract

The effect of water stress on the respiratory energy demand for the main biosynthetic and transport processes was estimated in the leaves of spring wheat (Triticum aestivum L. cv. San Pastore) acclimated and non‐acclimated to drought. ATP‐consuming processes were assessed from the effects of selective inhibitors of RNA synthesis, protein synthesis and proteolysis, Ca2+‐ATPase and P‐type ATPases on respiration. The proportions of energy consumed by these processes were compared with the theoretical ATP production calculated from the rate of oxygen consumption measured manometrically. Respiratory energy production increased significantly in both acclimated leaves and in leaves stressed by drought. In the fully grown wheat leaves, Ca2+‐dependent reactions and protein turnover consumed about 37% and 34% of the total respiratory energy, respectively. The costs of ion transport constituted another 15% of the total ATP production. Both acclimation and drought stress in non‐acclimated leaves resulted in a decrease of leaf sensitivity towards inhibitors of RNA and protein syntheses as well as a decrease in Ca2+‐mediated processes; but also in an increase of leaf sensitivity towards inhibitors of proteolysis and ouabain‐sensitive ATPase in non‐acclimated plants. This indicates a shift in ATP input into the energy‐requiring processes towards greater expenses for ion transport upon water deficit. However, in acclimated leaves under drought stress, distribution of respiratory energy became almost the same as in control plants.

Effects of Water Stress on Respiration in Soybean Leaves

“…Nevertheless, this observation agrees with some published studies in other species (Lawlor, 1976;Loboda, 1993;Flexas et al, 2005). However, several other authors have found different results on the effect of water stress on respiration, ranging from decrease (Brix, 1962;Brown and Thomas, 1980;Palta and Nobel, 1989;Escalona et al, 1999;Ghashghaie et al, 2001;Haupt-Herting et al, 2001) to stimulation (Upchurch et al, 1955;Shearmann et al, 1972;Zagdań ska, 1995). In all cases, as in this study, changes in respiration were much less than those in photosynthesis, causing a significant increase in the respiration/photosynthesis ratio under water stress, indicating that the role of respiration becomes more important as water stress develops.…”

Forcing variables in simulation of transpiration of water stressed plants determined by principal component analysis

“…1d). While the original R d parameterization is a linear function of A m , the modified function is exponential with t C , but both parameterizations agree with the observations of Zagdańska (1995) who indicated R d to increase as plants became water stressed, closing stomata and reducing transpiration, causing higher leaf temperatures.…”

“…The effect of water stress on the dark respiration R d is inconclusive. Some studies show a decrease of R d as a function of water stress (Galmés et al, 2007), whereas others report an increase (Zagdańska, 1995). According to Ribas-Carbo et al (2005), changes in R d are smaller than in photosynthesis, causing a significant increase in the ratio of respiration/photosynthesis under water stress, and indicating the role of respiration to become more important with increasing water stress.…”

Differential gene expression in Pyropia columbina (Bangiales, Rhodophyta) under natural hydration and desiccation conditions

“…Theoretically, maintaining the tolerance mechanisms required to buffer the effects of a stress imposes energy costs (e.g., Zagdańska, 1995). Acclimation to oxidative stress depends on a high availability of NADPH and ATP, since most of the intracellular metabolic reactions require energy.…”