Growth of Reed Canarygrass (Phalaris arundinacea L.) as Affected by Environment and Cutting : I. Growth responses to day-length and temperature

摘要

Growth responses of reed canarygrass to differential temperatures (Day/Night, 35/30, 30/25, 25/20, 20/15, 15/10°C) combined with two photoperiods (16 hr, LD; 9 hr, SD) under natural day light were studied. 5 plants were sampled at the same calender date, after 25 days of treatment (A-plot), and the other 5 plants were sampled at the same leaf stage, When 11.4 leaves expanded on the main-stem of each treatment (B-plot), to compare the growth and the nitrogen and carbohydrate accumulations. 1) Leaf formation was most promoted at 30/25°C and was more rapid under LD than under SD. The optimun temperatures for plant height, stem elongation, tiller number were lower than 30/25°C. At A-plot, dry matter production reached a peak at 20/15°C under LD, 25/20°C under SD, respectively and greater under LD than SD, while at B-Plot, it was greatest at 20/15°C under LD and 15/10°C under SD, respectively. 2) Under LD combined with high temperatures, stem elongation of shoot was promoted and the underground growth was suppressed resulting in greater Aboveground/Underground ratios, while under SD combined with lower temperatures the ratios became smaller, resulting from a checked shoot growth and a promoted rhizome elongation and longer underground stems which emerged from underground nodes and elongated at a greater angle to a perpendicular with a longer pathway to ground surface. 3) Tiller numbers at A-plot, were greater under LD than under SD, and greatest at 25/20°C under LD and at 20/15°C under SD, respectively, while at B-plot, they were greatest at lower temperatures such as 15/10°C or 20/15°C under both photoperiods. Rhizome numbers at A-plot were greater at higher temperatures under LD, while at B-plot they became greater at lower temperatures under SD. 4) Crude protein concentration was highest at 15/10°C under LD or 20/ 15°C under SD. At the optimun temperatures for dry matter production (20/15°C, 25/20°C), it was higher under SD. In general, TAC concentration increased with decrease of temperature and was high under SD. 5) At A-plot, crude protein accumulation in aboveground parts increased with increase of temperature, while that of underground parts tended to increase with decrease of temperature, reaching a maximum at 20/ 15°C. At B-plot, on the contrary, the accumulation increased with decrease of temperature in both above- and under-ground parts and was a little greater under LD than under SD. TAC accumulation increased with decrease of temperature and was greater under SD in all plant parts at both A- and B-plots, being especially conspicuous in underground parts. 6) These changes in growth pattern and reserve material accumulations in response to environmental conditions were discussed in relation to seasonal forage production, regrowth after cutting, and forage quality.