Recovery Processes after Leaf Cutting in Cereals and Forage Grasses : VI. The effects of season and temperature before or after cutting on the regrowth of orchardgrass plant

Abstract

Two kinds of experiments (A- and B-plots) were carried out using a single clone of orchardgrass to trace the effects of photoperiod and temperature before or after cutting on the subsequent regrowth processes. A-plot: The plants were grown for two weeks at four growth chambers (day-night temperatures; 30-25, 24-19, 17-12, and 9-9°C) and were cut at the end of the treatment, then were moved to outdoors in May and to glasshouse in October under natural day-light. The former is called spring experiment (LD) and the latter fall experiment (SD). B-plot: All the plants having been grown outdoors were cut and moved to the above four growth chambers to trace regrowth at different temperatures. It also consisted of LD- and SD-experiments, both being begun in June and October, respectively. 1) The plants under LD of both A- and B-plots all headed at the cutting date, whereas no heading occurred under SD. This difference in development between LD and SD may have induced fegrowth difference in various ways. 2) In A-plot, the growth at cutting date was best at 24-19°(LD) and 17-12°(SD), respectively. Under LD, early regrowth in leaf area was greatest at 17-12°, smallest at 30-25°, while under SD it was smallest at 9-9°and no significant difference existed among the rest three temperatures. The subsequent regrowth for three weeks was 17-12 > 24-19 > 9-9 > 30-25°under LD and 17-12 > 24-19 > 30-25 > 9-9°under SD in order. These ranks coincided with those of leaf area formation which was regulated by tiller number. Under LD, strong correlations were found between early leaf regrowth and nitrogen or TAC or both contents in stubble and roots at cutting time, but no significant correlation was found under SD. 3) In B-plot, early regrowth was greater at higher temperatures, but later regrowth became greater at lower temperatures and greatest at 17-12°then at 24-19°. 4) RGR from one week to three weeks after cutting had a keen correlation with NAR (r=0.935***) and an weaker correlation with RLGR (r=0.751***) during the same period. 5) The fact that the best regrowth was obtained at 17-12°followed by 24-19°in both plots under both day-lengths with abundant accumulation of nitrogen and TAC in cut herbage. stubble and roots may indicate these temperature range (mean temperature of 15°or a little higher) be optimum for forage production.