[Effects of drought stress on leaf gas exchange and chlorophyll fluorescence of Salvia miltiorrhiza].

Taking the seedlings of Salvia miltiorrhiza cv. Sativa (SA) and S. miltiorrhiza cv. Silcestris (SI) as test materials, this paper studied the effects of drought stress on their leaf gas exchange and chlorophyll fluorescence parameters. After 15 days of drought stress, the net photosynthetic rate (P(n)) and the maximal photochemical efficiency of PS II (F(v)/F(m)) of SA were decreased by 66.42% and 10.98%, whereas those of SI were decreased by 29.32% and 5.47%, respectively, compared with the control, suggesting that drought stress had more obvious effects on the P(n) and F(v)/F(m) of SA than of SI. For SI, the reduction of P, under drought stress was mainly due to stomatal limitation; while for SA, it was mainly due to non-stomatal limitation. Drought led to a decrease of leaf stomatal conductance (G(s)), but induced the increase of water use efficiency (WUE), non-photochemical quenching coefficient (q(N)), and the ratio of photorespiration rate to net photosynthetic rate (P(r)/P(n)), resulting in the enhancement of drought resistance. The increment of WUE, q(N), and P(r)/P(n) was larger for SI than for SA, indicating that SI had a higher drought resistance capacity than SA.

[Tissue culture and rapid propagation of Phytolacca americana].

OBJECTIVE: To explore the technique of rapid propagation for Phytolacca americana. METHODS: Aseptic seedling were used as explants. RESULTS: The best explants were the stems from strong aseptic seedling. The optimal culture media were MS + NAA (0.2 mg/L) +6-BA (1.0 mg/L) for primarily culture, MS + NAA (0.2 mg/L) +6-BA (2.0 mg/L) for the induction of clustered shoots 1/2MS with NAA 0.4 mg/L for rooting. CONCLUSION: The propagating coefficient of Phytolacca americana can be improved by inducing the clustered shoots from aseptic seedling.

[Fitness analysis of seed- and vegetative reproduction of clonal tree Symplocos laurina].

There are two ways in Symplocos laurina propagation, clonal and sexual reproduction. The study showed that under different habitat conditions, Symplocos laurina could adopt different ways to propagate and occupy space. In conditions with abundant water and nutrient resources, such as in evergreen broad-leaved forests or bamboo forests, the survival rate and space-occupying ability of both ramets and sexual seedlings were relatively high, with clonal ramets took advantage in terms of number and space, suggesting that clonal propagation was the dominant way in such environments. Oppositely, in habitats lack of sufficient nutrition, the survival rate and space-occupying ability of seedlings were low, and grown-up plantlets would preempt in number and space occupation. Bottleneck in sexual propagation appeared in the stage from seed to seedling, while clonal propagation appeared during the period from seedling to ramet. The way of Symplocos laurina invasion was to settle a plantlet, and then occupied the space rapidly by clonal growth, with clonal seedlings dominated in initial stage and lost the advantage after 15 ages.

[Effects of aspect on distribution pattern of Taxus chinensis population in Yele, Sichuan Province: an analysis based on patches information].

Employing GIS method and based on patches information, this paper studied the effects of aspect on the distribution pattern of Taxus chinensis population in Yele, Sichuan Province. The results showed that Taxus chinensis population mainly distributed on the aspects of northwest, northeast, east and north. These aspect patches were absolutely dominant on area, mean size, mean edge and the number of Taxus chinensis. There existed a significant correlation between aspect and Taxus chinensis distribution. Taxus chinensis distributed preferentially on north, northeast, northwest and east patches, then on west and southwest patches, and finally on flat and southeast patches. The distribution patterns of Taxus chinensis in Yele were clustering, except on south aspect patches. The intensity of clustering on north aspect patches was the highest, with the value of Clark-Evans (CE) index being 0.906. The intensity of clustering on northeast and northwest aspect patches was lower than that on north aspect patches, with the CE value 0.797 and 0.563, respectively. The CE values on the rest aspect patches were all not larger than 0.5. There existed a significant positive correlation between the intensity of clustering index, number of patches, total patch edge, and the number of Tarus chinensis distributed on the patches, with the value of correlation coefficient 0. 936, 0.735 and 0.802, respectively. There were no significant correlations among the intensity of clustering, patch area, mean patch size, mean patch edge, and mean shape index of aspect patches.

[Relationship between plant community succession and fertility variation of mountain yellow soil in east Chongqing].

Based on the analyses of soil physical and chemical properties, this paper studied the relationship between plant community succession and fertility variation of mountain yellow soil in east Chongqing. The results showed that the values of integrated soil fertility index of Pinus massoniana, Cunninghamia lanceolata, deciduous oak, Camellia sinensis and evergreen broad-leaved forest soils were 0.1256, 0.2085, 0.3514, 0.2479 and 0.9329, respectively, implying that soil development had a close relation to plant community succession.

[T-square study on spatial pattern and regeneration of Betula albo-sinensis Burkill population on west slope of Jiuding Mountain].

The T-square study of Betula albo-sinensis population on the west slope of Jiuding Mountain showed that the population was mainly in random distribution, and in aggregated distribution in a few lines because of the negative human activities and severe destructions. In this region, the old trees of Betula albo-sinensis population were accounted for about 24%, and the younger trees only accounted for 12%. There exited a huge difficulty in the self-regeneration of Betula albo-sinensis population. Therefore, some measures should be taken to protect the population and to speed up its self-regeneration.

[Soluble sugar content of clonal plant Neosinocalamus affinis at module and ramet levels].

In this paper, soluble sugar content of Neosinocalamus affinis was measured by anthrone colorimetry at two levels of module and ramet in order to reveal its ecological and physiological adaptability. The results showed that soluble sugar content decreased in the order of leaf > branch > culm. As for soluble sugar content, different modules responded to ramet age and position in different ways. The branch and culm of 1-year-old ramets contented more soluble sugar than those of other four ages, but soluble sugar content in leaf was independent to ramet age. For leaf and culm, lower parts of ramet contented more soluble sugar than middle and upper parts. Under high irradiance, the soluble sugar content of Neosinocalamus affinis leaf was more than that under low irradiance. Seasonal change had significant effect on soluble sugar content. The soluble sugar content of leaf presented a monthly change, with a bottom and upper value in January and in April, respectively, but there was no obvious difference between 2-year-old and 3-year-old ramets. The soluble sugar content of parent ramet leaves was positively correlative to that of daughter ramet in upper and middle parts of ramets. There was no significant difference between ramet ages at ramet level. Hierarchical response of physiological character to environmental changes existed at the module and ramet levels of Neosinocalamus affinis.

[A comparative study on life-form spectra of evergreen broad-leaved forest in different successions in Jinyun Mountain].

The life-form of plant communities in different succession stages in Jinyun Mountain was studied and the life-form spectrum was established. The results showed that according to the characters of life-form of plant communities, the vegetation in Jinyun Mountain belonged to typical subtropical evergreen broad-leaved forest vegetation. Evergreen phaenerophytes were absolutely dominant in the life-form spectrum and its quantity accounted for more than 80%. Among phaenerophyte, quantity of microphanerophyte was the most, and quantities of mesophanerophtye and nanophanerophyte were less. Different successions had different life-form spectra. With the development of succession, the percentage of phaenerophytes increased, and other life-forms decreased correspondingly. According to the development of life-form and comparative analysis of environmental factors in different succession stages, coniferous species would be replaced by evergreen phaenerophytes.