Influência da temperatura do ar sobre a duração das fases do desenvolvimento fisiológico da semente de mamona.

Abstract

Earlines is a key factor for agricultural production because a shorter growing season reduces the risks and costs of production. The reduction, of any phase of development, contributes to a shorter growing period. The objective of this study was to evaluate the influence of air temperature on the two initial stages of physiological development of the seeds of Ricinus communis L, better known as castor. Anthesis was defined as the time of opening of the fifth female flower; the date was recorded and the fruit was harvested three times a week until fruits reach their visual maturation. Immediately after harvest, seeds were manually extracted, weighed, measured (length, width and height) and transferred to an oven for 48 h at 80°C. After drying, the seeds were weighed. These data were used to calculate the volume of seed and its moisture content. Calculations were performed to detect and discart aborted seeds and seeds that grown before or after most of the seeds of the same age. The present study tested three temperature treatments: the 26, 30 and 34°C. 1.730 seeds were collected, but some of them were excluded for the following reasons: for abortion, for late or early growth, and processing errors in the collection We considered the point of 80% water content, was the threshold of cell division phase and the 22% water content, such as the physiological maturation. The reserve accumulation phase took 17 days at 26°C 14 days at 30°C and 13 days at 34°C. The duration of the reserve accumulation phase was 19 days at 26°C 18 days at 30°C and 13 days at 34°C. The final weight of the seeds was also influenced by different temperatures. The plants exposed to 34°C yielded considerably lighter seed (mean weight 150 mg) while those which were produced at 26 to 30 ° C and reached on average 280 mg, namely, a larger volume to those subjected to 34 ° C. On the other hand, plants subjected to 34 ° C was visually affected by temperature, with a reduced number of the bunch fruits, leaf area and less yellowing leaves. For this reason, it is questionable whether the reduction in the weight of the seeds was a direct effect of temperature or a consequence of the reduced capacity of the plant's own energy production, be it physiological or genetic factor. Castor beans were very sensitive to air temperature, and seed maturation may be considerably delayed even by a temperature which would not affect the overall growth of the plant. Further study of these phenomena are needed in order to determine the cardinal temperatures of this industrial culture.