热带林下人工种植阳春砂仁的生长与果实产量动态

调查了西双版纳不同海拔热带沟谷雨林和次生林下的阳春砂仁生长和果实产量动态.结果表明,西双版纳热带林下阳春砂仁自身年龄增长、林下光照不足和旱季水分胁迫影响阳春砂仁果实产量.随种植期增加,阳春砂仁果实产量和成熟植株密度降低.当林下光照水平在全日照的35%以下时,阳春砂仁果实产量随林下日照水平变化呈线性增加(P<0.05).沟谷下方阳春砂仁果实产量显著高于上方(P<0.05).海拔600～1000m,由于阳春砂仁的主花期从干热季3～4月推迟到雨季5月,果实产量显著增加.沟谷雨林和次生林下阳春砂仁果实产量差异不显著.因此,在海拔800～1000m沟谷中轮歇地次生林下有计划种植阳春砂仁,代替在沟谷雨林下种植阳春砂仁,既能解决沟谷雨林下光照和当地旱季水分不足对阳春砂仁果实产量的影响,又有利于热带沟谷雨林的保护.

Possible mechanism of inhibition on photosynthesis of Lycium barbarum under salt stress

Using different concentrations of salt treating Lycium barbarum seedlings, the photosynthetic rate and other physiological indexes of leaves were measured at different growth stages. The results showed that under salt stress, the photosynthetic rate,stomatal conductance,chlorophyll content and chlorophyll fluorescence kinetics parameters Fm, Fv, Fm/Fo, Fv/Fo and Fv/Fm of leaves decreased, while the soluble carbohydrate and polysaccharides of Lycium barbarum increased. The intercellular CO 2 concentration showed a trend from decrease to increase, but the Ls increased at first, and then decreased. Changes of the Ci and Ls showed that the decline of photosynthetic rate of Lycium barbraum was mainly caused by temporary stomatal limitations.In the long run, in long time, it was caused by nonstomatal limitations.Changes of other physiological indexes and significant correlations between them and Pn showed that the multiple reactions of these physiologic characteristics determined the photosynthesis declination of Lycium barbarum under salt stress. The results also indicated that the photosynthesis of Lycium barbarum was inhibited insignificantly under the soil salt content below 0.5%, which suggested that there were certain salt tolerance of Lycium barbarum.