Apex and root temperature and the early growth of wheat

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Abstract
Wheat was grown in temperature controlled water-baths in order to regulate the temperature of the roots, the growing apex and the zone of leaf extension. Twenty-two alternating day and night temperatures varying between 26 and 2¦C were studied. All plants experienced the same aerial environment. Leaf extension rates were measured on 6 days throughout the early growth stages and dry matter production was determined after 39 days. Night leaf extension was found to be related not only to the temperature of the meristem and leaf extension zone during the night, but also to the temperature experienced during the preceding day. Leaf extension during the day was determined by daytime temperature, and also the temperature conditions of the previous night. These growth patterns were explained in terms of leaf sugar concentrations, which were measured at the end of the experiment. Dry matter production was found to be exponentially related to the time-corrected mean daily temperature of the apex, leaf extension zone and roots. These results confirm the suggestion that the improved early vigour of wheat sown by conventional cultivation practices with a minimum of surface residues compared to direct drilled wheat, could at least partially have been due to the different patterns in soil temperature.