Responses of Leaf and Tiller Emergence and Primordium Initiation in Wheat and Barley to Interchanged Photoperiod
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文摘
The influence of constant (9, 13 and 19 h) and reciprocally-interchanged photoperiods [at terminal spikelet (TS) or triple mound (TM)] on leaf, tiller and primordium development were examined using photoperiod-responsive cultivars of spring wheat, ‘UQ 189’ and spring barley, ‘Arapiles’. In both species, constant longer photoperiod reduced the duration from sowing (S) to double ridge (DR), as expected. However, photoperiod sensitivity was not restricted to this mainly vegetative phase. There was also a marked increase or reduction in the duration of reproductive phases between TS/TM and heading (H) when plants were transferred to shorter or longer photoperiods respectively, compared with controls. These responses were largely independent of the photoperiod during previous phases although minor effects of the previous photoperiod were observed. For both species, the time course of leaf emergence was linear, or bi-linear, depending on the final leaf number on the main stem. The rate of leaf emergence was faster for the first six to eight leaves than for the leaves appearing subsequently. The rate of emergence of early-formed leaves was independent of photoperiod whereas the rate of emergence of later leaves varied with photoperiod. Photoperiod also affected the dynamics of tillering. The rate of leaf primordium initiation was little affected by variation in photoperiod, but the rate of spikelet initiation increased with increases in photoperiod. The rates of leaf and spikelet primordium initiation were both substantially higher in barley than in wheat. The fact that the reproductive phase from TS/TM to H was largely independent of the duration of the previous phase provides evidence that this phase might be genetically manipulated to increase the time for floret development and hence grain number.