Some effects of artificial variation in light interception, number of grains and husk constriction on the development of grain weight in normal and high-lysine barley

Abstract

SUMMARYThe grain weights of normal and high-lysine cultivars were compared in field and pot experiments in which the supply of assimilate per grain was adjusted by a variety of treatments involving application of fertilizer, thinning, degraining or defoliation. The results of these experiments indicated that in normal cultivars, grain weight was affected both by the supply of assimilate from the green tissues and by internal factors in the grain which limited the accumulation of this assimilate. Some evidence suggested that physical constriction of the expanding endosperm by the surrounding husk could be one of these factors; the effects of the husk on growth of the caryopsis was not clear.The development of grain weight in the high lysine cv. Riso 1508 was initially similar to that of normal cultivars, but the cessation of growth as maturity approached was more abrupt. Increased assimilate availability resulting from the application of fertilizer, thinning or degraining treatments effectively increased grain weight in this cultivar, but to a lesser extent than in low-lysine cultivars. Conversely, decreased assimilate supply as a result of defoliation produced less marked reductions in grain weight in the high-lysine type, suggesting that the reduced starch accumulation associated with the high lysine characteristic rendered superfluous some of the photosynthetic capacity in these types.