Reappraisal of film antitranspirants for wheat

Study to investigate the potential for reducing drought stress in wheat crops with film antitranspirants applied at the booting stage which appears to be most sensitive to water stress.

Year of Publication2008

One way of ameliorating the effect of drought stress on crops may be to suppress transpiration with antitranspirants. Film antitranspirants are sprayed onto plants to create a transparent barrier with low permeability to water vapour, thereby restricting water loss from leaves. However, the film simultaneously restricts carbon dioxide uptake and photosynthesis. Many of the materials are expensive at the high application rates used. Reviews and textbooks have, therefore, concluded that film antitranspirant use is limited to high-value plants and to situations where photosynthesis is not important e.g. for reducing desiccation and needle drop in Christmas trees. Much of the past research on film antitranspirants has been dominated by the physiology of the processes of transpiration and photosynthesis. We have reappraised the scope for antitranspirants on low-value, large-scale arable crops from the perspective of the physiology of crop development. We postulate that for many crops there are phases of development which may be so sensitive to low water potential that reduced photosynthesis is of less consequence. Although this has occasionally been stated previously, these authors do not appear to have published any attempts to investigate the potential for reducing drought stress in large-scale arable crops with film antitranspirants applied at the stages most sensitive to water stress. Reproductive stages in seed crops are likely to be appropriate candidate stages, and we have focused on the wheat crop. The stage of development in wheat which appears to be most sensitive to water stress is the period preceding ear emergence, visible externally as the stage of booting. Field experiments on the variety Claire in 2003-2005 on a low available water capacity loamy sand soil at Harper Adams tested the hypothesis that applying a film antitranspirant around the stage of booting would enhance yield of droughted crops. Application of an antitranspirant at different development stages and soil moisture deficits (SMD) gave very close linear relationships between yield response to the antitranspirant and both spray timing and SMD at spraying. The greatest responses were at the earliest stage tested of flag leaf appearance and the highest SMD tested of 118 mm, with a yield increase from a spray at this stage combined with this SMD calculated as 1.97 t/ha. There was an indication from previous experiments at Harper Adams between 1996 and 2002 that other varieties may give a greater response. These experiments provide ‘proof of concept’, but further research will be necessary to define the optimal application strategy.

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