Studies On Shade-tolerance Of 12 Garden Plant Species

Although the shade-tolerance is the basis of choice and optimal allocation of garden plant species, the shade-tolerance of a garden plant species has being judged and applicated depending on experiences. The shade-tolerance study is very important for developing tridimensional greening, increasing the relative green space and improving the ecological environment. With 12 species of garden plant species (including Tulbaghia vielacea Harvey, Alternanthera ficoidea, Houttuynia cordata Thunb, Philodendron tuxtlanum, Disporum cantoniense (Lour.) Merr., Chloranthus spicatus (Thunb.) Makino, Clerodendrum wallichii Merr., Commelina paludosa Bl., Tradescantia sillamontana Matuda, Costus speciosus (Koening) Smith, Costus sp., Costus comosus var. bakeri) , a research of shade-tolarance has been carried out into the traits of growth and development, physiological characteristics, photosynthetic characteristics and ornamental feature at different the full sun light intensity of 50%, 35%, 15% and 3%. The results show that:1. As the full sun light intensity increasing, the color of a leaf deepens, both the plant height and the leaf area increase, the florescence date delays. When the light condition is moderate, the numbers of flowers, leaves and ramet increase, but the number of flowers ,and leaves and ramet decrease if light condition is too strong or too weak.2. With the full sun light intensity increasing increasing, chlorophyll contents, carotenoid, specific leaf area and water content increase, but light compensation point, the leaf thickness, the chlorophyll a/b ratio and the sugar content decrease; the biomass increment, the daily average net photosynthetic rate and the apparent quantum yield increase as well, after reaching to the peak they decrease. Peroxidase (POD) falls at the beginning stage, after reaching to the valley it increases.3. By means of principal component analysis, membership function, cluster analysis, the shade-tolerance of 12 garden plant species are comprehensively evaluated and sequenced. The shade-tolerance sequence of the plant species tested from strong to weak is in following order: Clerodendrum wallichii Merr., Chloranthus spicatus (Thunb.) Makino, Philodendron tuxtlanum, Costus speciosus (Koening) Smith, Costus sp., Costus comosus var. bakeri, Disporum cantoniense (Lour.) Merr., Tradescantia sillamontana Matuda, Houttuynia cordata Thunb, Commelina paludosa Bl., Alternanthera ficoidea, Tulbaghia vielacea Harvey. The results are consistent with cultivation observation basically, which indicates it is useful to predict the shade-tolerance of a plant species with the evaluation method used in this paper.4. Five shade-tolerance identification indices, biomass increment, specific leaf area, chlorophyll a/b ratio, peroxidase (POD) and the daily average net photosynthetic rate, have been screened, and the stepwise regression equation for a plant species shade-tolerance evaluation has been established as well. The stepwise regression equation provides a more accurate, more convenient and faster way for a plant species shade-tolerance evaluation.