遮光对窄头橐吾形态及光合特性的影响

对不同遮光条件下窄头橐吾Ligularia stenocephala形态及光合特性进行研究。结果表明：遮光处理对窄头橐吾形态特性有明显影响．在55％的遮光条件下。窄头橐吾具有较高的相对生长率。窄头橐吾的净光合速率日变化曲线在不同光照条件下均呈“双峰”型，在13：00出现明显的光合“午休”现象。在0（全光照），55％和75％遮光条件下，窄头橐吾的光补偿点分别为13．20，15．10和8．63μmol·m^-2·s^-1；光饱和点分别为919．66，749．20和727．34μmol·m^-2·s^-1；最大净光合速率分别为7．13，9．29和8．21μmol·m^-2·s^-1；表观量子效率分别为0．0401，0．0460和0．0463。与对照相比．55％和75％的遮光使窄头橐吾的最大净光合速率增高了30．3％和15．1％。不同遮光条件下，窄头橐吾的光饱和点和光补偿．点都比较低．表明其对光照的要求不高．属于耐荫植物，适宜在弱光照环境下栽培与应用。图2表4参16

Morphological and photosynthetic characteristics of Ligularia stenocephala with shading

Ligularia stenocephala（Compositae）, a perennial herb, is a potential ground-cover plant. Shading （0. 55%, and 75%） was applied to L. stenocephala to determine a theoretical basis for morphological and photosynthetic characteristics in plantation and landscape application. Results indicated that relative growth rate was higher with 55% shading. The diurnal variation of net photosynthesis（Pn） in L. stenocephala with all shade conditions presented a double-peak curve with a midday depression for Pn at 13：00. For shad ingof0, 55%, and75%, the light compensation points （LCP）were 13.20, 15.10, and 8.63 μmol·m^-2·s^-1; the light saturation points （LSP） were 919.66, 749.20, and 727.34μmol·m^-2·s^-1; the maximum net photosynthetic rates were 13.20, 15.10, and 8.63μmol·m^-2·s^-1; and apparent quantum efficiencies were 0.040 1, 0.046 0, and 0.046 3, respectively. The maximum Pn rate significantly （P〈0.05） increased, and LSP were significantly （P〈0.05） decreased with 55% and 75% shading, with shading of 75%, LCP were significantly lower than shading of 0 and 55%. This result indicated that L. stenocephala was adapted to weak light. Thus, L. stenocephala is a shade tolerant plant that can be planted under low light conditions. ECh, Key 2 fig. 4 tab. 16 ref. ]