Wilting of a plant due to water stress. A courgette plant (Cucurbita pepo ovifera) seen after several weeks without rain. The leaves have wilted considerably. This is because the roots cannot take up enough water to replace losses through the leaf stomata. The plant's only defence is to close the stomata, this is triggered by the release of abscisic acid from the chloroplasts. Compare with B740/158, the same plant four hours after watering.