Effects of photoperiod and maturity genes on plant growth, partitioning, radiation use efficiency, and yield in soyabean [Glycine max (L.) Merrill] 'Clark'

Plants of four isolines of soyabean [Glycine max (L.) Merrill] 'Clark', viz 'L71-920' (maturity gene complement e(1)e(2)e(3)), 'L80-5914' (E(1)e(2)e(3 )), 'Clark' (e(1)E(2)E(3)), and 'L65-3366' (E1E2E3), were grown in short (1 2.25 h d(-1) natural light) and long days (12.25 h d(-1) natural light supp lemented with 2.75 h d(-1) low-irradiance artificial light) from first flow ering to maturity in a polythene tunnel maintained at 30/24 degrees C (day/ night). Whereas there were few differences among the isolines grown in shor t days, in long days the dominant alleles increased crop duration, biomass and seed yield substantially. Increases in biological and economic yield we re not solely a consequence of longer crop duration: the dominant alleles a lso increased crop growth rate and radiation use efficiency in long days (f rom 1.3 g MJ(-1) total radiation in e(1)e(2)e(3) to 28 g MJ(-1) in E1E2E3). Greater radiation use efficiency resulted from a relatively longer leaf ar ea duration. better distribution and orientation of a larger mass of leaves within the canopy, and smaller partitioning of assimilates to reproductive structures. The work reveals the substantial effects of the three loci E-1 /e(1), E-2/e(2) and E-3/e(3) on the response of plant growth, as well as de velopment, to environment. Their relevance to crop adaptation is discussed. (C) 2000 Annals of Botany Company.