The relationship between productivity and some components of canopy structure in ryegrass (Lolium spp.)

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Abstract
Summary: Two experiments are described in which the potential production of genotypes selected from within S. 321 perennial ryegrass for differing leaf length was assessed (a) in micro-swards composed of populations of similar genotypes and (b) in micro-swards of individual genotypes. In Experiment 1 the long- and short-leaved populations were also compared with the base population of S. 321 and with several other natural populations and bred varieties.Under infrequent cutting the population of long-leaved genotypes was more productive than the short-leaved and base populations. Under frequent cutting, however, the population of short-leaved genotypes was most productive. Similarly, whilst Ba 6280 ryegrass was highly productive and the natural Ynyslas population unproductive under infrequent cutting the situation was reversed under frequent cutting. The population of long-leaved genotypes and Ba 6280 had a higher leaf area index (L) than other populations and varieties at complete light interception.Considerable differences in productivity existed between individual genotypes, and there was also an interaction between genotypes and cutting frequencies. The relationships between yield and both leaf length and chlorophyll content are presented and the physiological basis of inter-genotypic and inter-population differences in production are discussed.