EFFECT OF PLANTING DATE ON FLOWERING TIME IN WHEAT

The time from seed germination to anthesis varied for spring wheat in experiments in climate chambers with plants grown hpdroponically at di fferent nitrogen regimes. Time to anthesis was related to the time of seed germination during the calendar year. Seed germinating earlier in the calendar year required a shorter time to anthesis compared to see d germinating later in the year, a pattern found for all the spring wh eat cultivars investigated. Time to anthesis was also found to be inde pendent of factors such as year in which the seed was produced, nitrog en regime used, or year or site of cultivation. We suggest the existen ce of an annual rhythm for flowering in spring wheat. This variation i n time to flowering can be due either to external factors or more like ly to an endogenous rhythm in the plant. When investigating plant proc esses, it is of importance to be aware of such a rhythm, since it may influence the results depending on when during the year the experiment s are performed.