Abstract: The diurnal variations of net photosynthesis rate(Pn),stomatal conductance(GS),transpiration rate(Tr),intercellular CO₂ concentration(Ci),photon flux density(PFD),and water utilization efficiency(WUE) of 16 alfalfa cultivars with different fall-dormancy levels were measured using Li-6400 Portable Photosynthesis System and the yields were measured at same time.The results show that cultivars Algonquin,Overseason,Victoria,WL525,Salado,WL414,CW403,721Amerilea,Empress2000,Amerigraze701,and Powerplant had the diurnal variation laws with the bimodale shape in the Pn;and CW400,CW680,Lobo,Hunter River,and Millenium the ternary-peak shape in the Pn.An obvious "midday-rest" phenomenon in Pn was shown for each alfalfa cultivar and no correlation was detected between it and full-dormancy level.Cultivars Millenium,Amerigaze701,and Powerplant had higher Pn which was above 20 μmolCO₂·m^-2·s^-1;Amerigaze701,Lobo,and WL525 had higher Tr which was above 10 mmolH₂O·m^-2·s^-1;CW403 and 721Amerilea had higher WUE which was above 5 μmolCO₂·mmolH₂^-1.In the circumstance of southwest region of Hunan province,cultivars with higher Pn and Tr should be planted widely.

Key words: Alfalfa, Fall-dormancy level, Net photosynthetic rate, Transpiration rate, WUE

摘要： 利用Li-6400光合速率测定系统测定了16种不同秋眠级紫花苜蓿(Medicago sativa L.)品种的净光合速率、气孔导度、蒸腾速率、胞间CO₂浓度、光量子通量密度、水分利用率;同时对不同秋眠级紫花苜蓿草产量进行测定。结果表明:阿尔冈金(Algonquin)、四季旺(Overseason)、维多利亚(Victoria)、WL525、萨兰多(Salado)、WL414、CW403、721丰叶(721Amerilea)、皇后2000(Empress2000)、牧歌,701(Amerigraze701)、丰宝(Powerplant)的光合速率日变化曲线呈双峰型,而CW400、CW680、路宝(Lobo)、猎人河(Hunter River)、盛世(Millenium)呈三峰型,16个品种净光合速率日变化均出现午休现象,其变化规律与秋眠级没有相关性;盛世、牧歌701、丰宝净光合速率较高在20μmolCO₂·m^-2·s^-1以上;牧歌701、路宝、WL525蒸腾速率较高在均在10 mmolH₂O·m^-2·s^-1以上;CW403、721丰叶(721Amerilea)水分利用率较高,达5μmol CO₂·mmol H₂O^-1以上。在湘西南湿热地区环境气候条件下,盛世、牧歌701、丰宝、4季旺等光合能力较强、蒸腾速率高的品种可作推广种植。

关键词: 苜蓿, 秋眠级, 净光合速率, 蒸腾速率, 水分利用率