Abstract:

【Objective】 Revealing the laws of inverted senescing sequence of wheat leaves and researching into its significances in theory and practice. 【Method】 The study arranged comparative experiments of wheat materials presenting inverted and conventional leaf senescing sequences with the measurements of canapy temperature and some important biological parameters since 2005. 【Result】 There was a type of wheat that presents an inverted leaf senescing sequence differing from the conventional leaf senescing sequence of the majority of wheats in nature, i.e., a part of the leaves at the latest age were the penultimate leaves rather than the flag leaves. Together with this inverted leaf senescing sequence, it presented a leaf color distribution with yellow upper part and green lower part during the late fruiting stage, which is completely opposite to the conventional leaf color distribution of wheat that had green upper part and yellow lower part. As its development moved forward, its leaf chlorophyll contents, soluble protein contents, transpiration rates and net photosynthetic rates presented an unconventional pattern that they became higher in the penultimate leaves than in the flag leaves, and it always had “cold” canopies for a period of time before its ripening (cold tail state) or in whole fruiting stage (cold type state). The above mentioned special physiological processes caused that the kernel weights of the stems presenting the inverted leaf senescing sequence were obviously higher than those of the stems presenting a conventional leaf senescing sequence in the wheat with an inverted leaf senescing sequence, thereby causing this type of wheat to increase its kernel weight compared with wheat with a conventional leaf senescing sequence, and this was closely related to the “relay” kernel filling mechanism differing from the kernel filling model of the conventional wheat whose flag leaves worked as the main nutrient sources for kernel filling in its whole fruiting process. 【Conclusion】 The study has provided an new approach to researching into wheat fruiting and senescence theory, further increasing wheat yield and breeding cold type and cold tail wheat.

Key words: wheat, inverted senescing sequence of leaves, canopy temperature, biological parameters