Shade-tolerance of 25 low subtropical plants

In this paper the authors presented a comparative study on shade-tolerance of low subtropical plants of different life forms, to provide experimental data in the selection for urban greenery. And the authors chose seedlings of 25 species, consisting of garden and understory plants from local forests and low subtropical areas in order to determine morphological characteristics of leaves and photosynthesis as well as photosynthetic light response curves using a LI-6200 portable photosynthetic system. The following measurements were made: physiological indices of leaf thickness (LT) , leaf area (LA) , specific leaf area (SLA) , water content (LWC) , chlorophyll content (Chl) , chlorophyll a/b ratio (Chl a/b) , photosynthetic rate (Pn) , dark respiration rate (R_d) , light compensation point (LCP) , light saturation point (LSP) and apparent quantum yield (Φ) . The measured data were analyzed for correlation and a cluster analysis was applied.Resultsshowed that all 25 plant species could be classified into three groups of shade-tolerance by hierarchical cluster analysis: 1) ten plants of strongly shade-tolerant: Thunbergia erecta, Ardisia crenata, Colocasia antiquorum, Clerodendrum japonicum, Baphicacanthus cusia, Rhaphidophora hongkongensist, Excoecaria cochinchinensis, Calanthe discolor, Curcuma kwangsiensis and Adiantum flabellulatum; 2) six plants are intermediate in shade-tolerance: Pothos chinensis, Brunfelsia calycina, Amomum villosum, Tetrastigma obtectum, Syngonium podophyllum and Piper austrosinense; 3) nine plants have low shade-tolerance: Eranthemum austrosinensis, Chloranthus spicatus, Coffea arabica, Neocheiropteris palmatopedata, Setaria palmifolia, Amomum tsao-ko, Homalomena occulta, Curculigo capitulate and Ardisia mamillata. There was a significant positive correlation between Pn and Chl a/b ratio as well as R_d, and a significant negative correlation between Pn and Chl b; the positive correlation between LCP and LSP was also significant; the positive correlation of Chl b and Chl a as well as Chl a+b was extremely significant, but there was a significant negative correlation betweenChlb and Chl a/b ratio; the positive correlation of SLA and LA was significant and the negative correlation between SLA and LWC was extreme significant.