Relationship of Boron Nutrition to Radiosensitivity of Sunflower Plants.

Abstract

Seven-day-old Mammoth Russian sunflower seedlings were grown in nutrient solutions with or without boron, for 2 to 5 days, after which they were x irradiated and again supplied with boron. Withholding boron for short intervals prior to x irradiation with doses that normally produce pronounced radiation symptoms, had a marked alleviating effect on the development of radiation injury. The absence of boron resulted in retardation of some phase of cellular activity and rendered the plants more radioresistant. This normally radiosensitive phase of cellular activity which may be rendered relatively radioresistant by withholding boron is, then, berondependent. An attempt was made to identify this growth phase by irradiating a series of germinating seedlings at different growth stages. lt appeared to be the phase of cellular maturation rather than cell division, suggesting that boron is required for some process or processes concerned with cellular maturation or differentiation. The apparent effect of boron on sugar translocation appears to be related to the effect of boron on cellular activity rather than to a direct enhancement of diffusion through membranes through formation of a sugar-borate complex. (auth)