Long-day Treatment of Italian Ryegrass in Natural Environment of the Fall

Abstract

Effect of long-day treatment in the fall on the changes of some morphological properties, on the growth and on the heading of Italian ryegrass were studied. Varietal differences in the response to long-day treatment were also investigated. 1) Plants grown under light-berak treatment (i.e., break of dark period by artificial illumination) showed heigher plant height, fewer tillers, thinner leaf and wider leaf area compared to the plant grown under natural photoperiod. No clear difference in the weight of a leaf were found. 2) Shoot weight were heavior in the treated plant than in the non treated plant at the later period of the treatment. It was recognized that the above results were brought about mainly by the earlier transition of plants from vegetative to reproductive stage by light-break treatment. And it was also confirmed that improvement of plant form for light-interception by stem elongation increased net assimilation rate. 3) In almost all cases, plant height, weight of a tiller, shoot weight and number of heading tillers became greater relating to the length of treatment duration. 4) Varieties low in requiremtns for floral induction which were originated in the low latitudes were considered to be more sensitive to long-day treatment in the fall. 5) A wide range of individual plant variations in a variety in their response to long-day treatment in the fall were found. 6) With respect to light sources for the long-day treatment, R (red light) lamp of 600〜700nm was considered to be the most effective, and B (blue light), BR (combination of blue and red light) and BLB (ultra violet) lamps relatively the less effective.