Studies On Shade Tolerance Of The Hosta Plants

The Hosta plants are perennial herbs of Liliaceae, which have highly decorative values of both leaves and flowers and thrive in the shade, they are excellent shade plants. Almost none study were conducted on shade-tolerance of the Hosta plants.The Hosta plants can be divided into four groups according to their leaf-colors, respectively yellow, variegated, gray-green and green types. Chlorophyll, leaf epidemis and photosynthesis of fifty Hosta plants were determined under tree canopies. Yellow-leaf type Hostas have lowest chlorophyll contents and highest value of Ca/Cb, secondly the variegated-leaf Hostas, gray-green-leaf and green-leaf Hostas have no significant differences in chlorophyll contents and value of Ca/Cb.The same is turn of stomatal density ratio of upper/lower of four leaf-color type of the Hosta plants. Net photosynthetic rates(PN) of four leaf-color types Hostas were in order,yellow-leaf>variegated-Ieaf>green-leaf>gray-green leaf, gray-green-leaf Hostas are the most shade tolerable, and the yellow-leaf Hostas are the least.The effects of shade on the photosynthesis, chlorophyll contents, leaf epidermis, anatomical and growth characters of four Hosta cultivars were determined under different light conditions (5, 30, 50% of full light) within pots. Light saturation points ranged from 400-800 mol m-2s-1 among four cultivars, of which H. sieboldiana 'Elegans' ('Elegans') and H. Plantagenea 'Aphrodite'('Aphrodite') had the lowest saturation point and compensation point. The maximal photosynthetic rate (Pmax) was significantly higher in shade than in full light in 'Elegans' and 'Aphrodite', and was at maximum levels in seedlings grown in 30% of full light. While the best shade treatment for H. 'Antioch' ('Antioch') and H. 'Golden Edger' ('Golden Edger') was 50% of full light. The diurnal gas exchange patterns in four cultivars were greatly influenced by the light condition.'Golden Edger' has lowest chlorophyll content and highest value of Ca/Cb, while 'Elegans' the opposite. Chlorophyll contents were increased and value of Ca/Cb were decreased with shading. Shading affected leaf epidermis and anatomical character as well. Stoma were mainly on lower epidermis and stomatal density were highest in 5% shading, lowest in 30%. Four Hosta plants have typically shade anatomical structure, the influence of shading to leaf thickness differed in cultivars, leaf was thickest in 30% shading . growth character of four Hosta cultivars at different light intensities were significantly affected. With shading levels increasing, biomass of the plants' decreased.Light compensation points, light saturation points, chlorophyll contents and value of Ca/Cb can all be important index of shade-tolerance, leaf epidermis and anatomical character had close relation with shade-tolerance.According to their photosynthetic responses to shade treatments, the shade tolerant ability of four cultivars was in the order: 'Elegans'>'Aphrodite'>'Antioch'>'Golden Edger'.Theory guides were provided of Hosta plants of their cultivation and propagation in gardens.