氮肥、刈割强度对桂牧1号杂交象草光合特性的影响

Effect of nitrogen fertilization and cutting intensity on the photosynthetic characteristics of Pennisetum purpureum cv.Guimu No.1

采用两因素的随机区组设计,研究了氮肥(250kg/hm2、不施氮肥)、不同刈割强度(即刈割时离地面5,20和50cm)对桂牧1号杂交象草光合特性的影响。结果表明,6个处理叶片净光合速率日变化曲线均为双峰曲线,但随着刈割强度的增加,光合速率先升高后降低,且在施氮肥的情况下,光合"午休"明显减弱。施氮肥能显著增加桂牧1号杂交象草的叶绿素含量和最大净光合速率。在施加氮肥的情况下,随着刈割强度的增加,叶片表观量子效率有增加的趋势,羧化效率先增大后降低,光补偿点、光呼吸速率和暗呼吸速率则呈现相反的变化趋势;而在不施氮肥的情况下,随着刈割强度增加,表观量子效率、光补偿点、羧化效率、光呼吸速率和暗呼吸速率均呈现先减少后增加的趋势。这些试验结果表明,氮肥、刈割强度均对桂牧1号杂交象草光合特性产生了一定的影响,在中强度刈割条件下,对桂牧1号施用250kg/hm2氮肥,可以显著提高其光合能力。

The effects of nitrogen fertilization （250 kg/ha and unfertilized） and cutting intensities （5 cm, 20 cm, or 50 cm above ground level） on the photosynthetic characteristics of Guimu No. 1 （Pennisetum purpure um cv. Guimu No. 1） were studied in a two factor randomized experiment. All the diurnal variations of net photosynthetic rate （Pn） in the six treatments followed a bimodal curve distribution. However, with an in- crease of cutting intensities, the Pn initially rose but then declined and with nitrogen fertilization, the noon break phenomenon of photosynthesis was reduced. Nitrogen fertilization increased chlorophyll content and the maximum net photosynthetic rate （Amax）. With an increase of cutting intensities in the N-fertilization treat ments, apparent quantum efficiency （AQE） increased, while carboxylation efficie but finally declined; the reverse was true for the light compensation point （LCP）, ncy ph （CE） initially increased otorespiratory rate （Rp） and dark respiration rate （Rd）. With an increase of cutting intensities in treatments with no N fertilization, AQE, I.CP, CE, Rp and Rd all declined initially but then increased. This indicated that both nitrogen fertilization and cutting intensity have some influence on the photosynthetic characteristics of Guimu No. 1 with the best effect from a combination of medium intensity cutting and 250 kg/ha nitrogen.