Study On Shade-tolerance Of Several Ornamental Grasses Of The Genus Pennisetum

Ornamental grasses are new kinds of landscaping materials with high ornamental values, having low requirements of the soil temperature and moisture, with fewer pests and diseases. They have many species and can be grown in different application landscapes because their height, color, plant type and texture are rich in changing. Pennisetum plants (Pennisetum Rich.), belong to Gramineae plants, are excellent materials of building a water-saving and environment-friendly garden for their being resistant to drought. A large number of shading fields are caused in cities because the combine of arbors, shrubs and grasses, as well as intensive building block, which highlights the importance of shade-tolerant plants in gardens. Nothing on shade-tolerance of Pennisetum has been reported at present both at home and abroad. In this paper we set four shading levels, 0%, 25%, 50% and 75%, respectively, by using black shade cloth and researched the effects of shading on the growth, distribution of biomass, ornamental characteristics, photosysthetic characteristics, contents of photosynthetic pigments, and water contents of five species of Pennisetums, Pennisetum villosum, Pennisetum alopecuroides'Ziguang', Pennisetum setaceum, Pennisetum orientale and Pennisetum alopecuroides'Little Bunny'. We sort their tolerant abilities and filter out indicators that can be used to evaluate the shade-tolerance abilities. The main conclusions of the study are as follows:1. Effects of shading on the indicators of ornamental grasses with Pennisetum as an example.(1) Effects of shading on the morphological indicators of Pennisetum. Leaf length and leaf width of five species increased under shade, while leaf thickness, specific leaf weight are on the contrary. Internode length, plant height, crown width, number of tillers, leaf height and plant size are different during species.(2) Effects of shading on the growth rate of Pennisetum. In the first month, Pennisetum villosum, Pennisetum setaceum, Pennisetum orientale, Pennisetum alopecuroides'Little Bunny'grow faster under heavy shading than light shading. However Pennisetum alopecuroides'Ziguang'grow fastest in full light conditions.(3) Effects of shading on distribution of biomass. Under shade conditions biomass of five species Pennisetum transferred to shoots more than to root, and leaf dry weight increased.(4) Effects of shading on ornamental characteristics. Shading reduced the inflorescence number of Pennisetum and pulled off wither stage, first and full flowering stage. Inflorescence length, inflorescence width and days of flowering stage are different during species.(5)Effects of shading on photosynthetic characteristics of Pennisetum. Under shading conditions all species of Pennisetums had lower light compensation points.(6)Effects of shading on contents of photosynthetic pigments. Total content of chlorophyll of Pennisetum villosum, Pennisetum alopecuroides'Ziguang'and Pennisetum alopecuroides'Little Bunny'increased under shading conditions, however other species were in opposite trend.(7)Effects of shading on water content. Water content of all species of Pennisetum increased under shading conditions.2. Study on the shade-tolerance ability of ornamental grasses, with Pennisetum as an example.(1)The result indicates that the shade tolerance is: P. alopecuroides'Little Bunny', P. alopecuroides'Ziguang', P. setaceum, P. villosum, P. orientale. The former three species (cv.) of Pennisetum can be planted under 50% shading, while the latter two species (cv.) can be planted under 25% shading.(2)The results identifies larger relevant indicators of shade tolerance for Pennisetum. Number of tillers, leaf length, leaf thickness, total content of chlorophyll, water content of leaves, specific leaf dry weight, leaf dry weight ratio, inflorescence length, plant dry weight in upground parts, root/shoot.