Moderately High Temperatures Inhibit Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase (Rubisco) Activase-Mediated Activation of Rubisco

We tested the hypothesis that light activation of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is inhibited by moderately elevated temperature through an effect on Rubisco activase. When cotton (Gossypium hirsutum L.) or wheat (Triticum aestivum L.) leaf tissue was exposed to increasing temperatures in the light, activation of Rubisco was inhibited above 35 and 30°C, respectively, and the relative inhibition was greater for wheat than for cotton. The temperature-induced inhibition of Rubisco activation was fully reversible at temperatures below 40°C. In contrast to activation state, total Rubisco activity was not affected by temperatures as high as 45°C. Nonphotochemical fluorescence quenching increased at temperatures that inhibited Rubisco activation, consistent with inhibition of Calvin cycle activity. Initial and maximal chlorophyll fluorescence were not significantly altered until temperatures exceeded 40°C. Thus, electron transport, as measured by Chl fluorescence, appeared to be more stable to moderately elevated temperatures than Rubisco activation. Western-blot analysis revealed the formation of high-molecular-weight aggregates of activase at temperatures above 40°C for both wheat and cotton when inhibition of Rubisco activation was irreversible. Physical perturbation of other soluble stromal enzymes, including Rubisco, phosphoribulokinase, and glutamine synthetase, was not detected at the elevated temperatures. Our evidence indicates that moderately elevated temperatures inhibit light activation of Rubisco via a direct effect on Rubisco activase.

CAP Reform vs WTO: Crop Diversification or Crop Rotation? : Legal opinion prepared by Dr. Christian Häberli at the request of APRODEV, the Association of World Council of Churches related Development Organisations in Europe

The European Commission’s proposals for the Legislative Framework of the Common Agricultural Policy (CAP) in the period 2014-2020 include, inter alia, the introduction of a “strong greening component”. For the first time, all EU farmers in receipt of support are to “go beyond the requirements of cross compliance and deliver environmental and climate benefits as part of their everyday activities crop diversification as a contribution to all EU farmers in receipt of support go beyond the requirements of cross compliance and deliver environmental and climate benefits as part of their everyday activities.” In a legal opinion prepared at the request of APRODEV, the Association of World Council of Churches related Development Organisations in Europe (www.aprodev.eu), Christian Häberli examines the WTO implications of this proposal, as compared with an alternative proposal to rather link direct payments to crop rotation. The conclusions are twofold: 1. Crop rotation is at least as likely to be found Green Box-compatible as crop diversification. Moreover, it will be more difficult to argue that crop diversification is “not more than minimally production-distorting” because it entails for most farmers less cost and work. 2. Even if (either of the two cropping schemes) were to be found “amber”, the EU would not have to relinquish this conditionality. This is because the direct payments involved would in all likelihood not, together with the other price support instruments, exceed the amount available under the presently scheduled maximum.