Ripening in maize: interrelationships between time, water content and weight of dry material in ripening grain of a flint × dent hybrid (Inra 200)

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Abstract
SUMMARY: Results are reported of ripening studies with maize (var. Inra 200) at Oxford, 1967–9. Sowings were made in late April or early in May, and crops grown at a standard density of 7–2 plants/m2. Areas were provided with cloche protection, for a 4- to 5-week period from time of sowing, to produce material for studies of the effects of flowering time on ripening patterns. From plants of known flowering date collections of 30–40 ears were taken at intervals from 30 until 100+ days after silking.Information is presented on water content, grain dry weight and number of grains/ear at the various times of harvest. Asymptotic, polynomial and inverse-polynomial regression models have been fitted to the data to elucidate the interrelationships between time (measured from date of silking), grain water content and grain dry weight.In plants flowering in mid-July grain continued to increase in dry weight until water content was reduced to 35 %, whereas in plants flowering early in August maximum dry weight was attained at a water content of around 40 %.Maximum dry weight of grain was approximately 10% higher in the earlier flowering plants; the corollary is that in the marginal areas of maize grain production in England maturity in such varieties as Inra 200 is often imposed by the environment with a consequent loss in potential yield.In the early flowering plants, the time taken from silking to reach the harvestable stage of 40 % grain water content was 69 d in 1967, 79 d in 1968 and 64 d in 1969. Rate of water loss from the grain during ripening was closely related to prevailing air temperatures. In the later flowering plants, differing by an average of 11 d in time of silking, 8 days longer was required for grain to be reduced to 40% water content, giving an average difference of 19 days in permissible dates of harvest.The results suggest that, in varieties of similar ripening pattern to Inra 200, an advance of about 7 days in flowering time is required to establish the maize grain crop beyond its present confines in south-east England.