Abstract: Arthraxon hispidus, is a wild grass with potential for development as a turf plant for sloping ground. In this study, 20 treatments were set up by a factorial combination of five shade levels (0, 10%, 30%, 50%, 70%) and four drought levels (adequate moisture, mild drought, moderate drought and severe drought). The purpose was to study the combined effects of shade and drought on growth of A. hispidus, and identify trade-offs between clonal growth and sexual reproduction. Various data, including clonal growth traits, number of seed-heads, and biomass structure were gathered, and differences in cloning efficiency index (CEI), reproductive allocation (RA), reproductive efficiency index (REI), reproduction index (RI) and ratio of breeding (RR) under the 20 treatments were analyzed. It was found that: 1) Shade and drought stress had significant effects on clonal daughter ramet number and CEI. Moderate and severe drought and over 10% shading significantly reduced daughter ramet number. Drought had no effect on CEI and shade decreased CEI, and a shade x CEI interaction (P<0.01) was observed, expressed as a reduced daughter ramet and genet number, and reduced CEI. 2) Shading and drought had significant effects on flower spike numbers and floret numbers of mother ramets, daughter ramets and genets, reproductive organ biomass (ROB), non-reproductive organ biomass (NROB) and total biomass (TB) (P<0.05). Light and moderate drought or 10%-30% shade or the combination of mild shade and mild drought significantly increased flower spike number and floret number of mother ramets, and of daughter ramets and genets. Mild drought or 10% shading or the combination stress of mild drought and light shade all significantly increased TB and ROB. Moreover, a synergistic interaction between shade and drought strongly increased flower spike number and floret number of genets, and TB, ROB and NROB. The effect of drought on TB and NROB was followed, and shading had greater influence on ROB. 3) Shading and drought significantly (P<0.05) affected RA, REI, RI and RR: mild and moderate drought or 10% shading significantly increased the genet reproductive parameters, but severe drought or more than 30% shading significantly reduced reproductive parameters (P<0.05). Compared with either single stress, the combined stresses of light shading and mild drought promoted sexual reproduction. Mild drought alleviated reduction in sexual reproduction observed under moderate and severe shading. Reproductive parameters typically displayed a synergistic effect, with shading the larger effect, and the drought effect smaller. 4) A. hispidus displayed an altered balance between clonal growth and sexual reproduction, depending on the degree of shading and drought. Greater than 30% shade prolonged the period of clonal growth by 10-34 days. 5) Under all 20 treatment combinations of shading and drought, A. hispidus maintained both clonal and sexual reproduction concurrently. Adequate water and light promoted clonal growth. Light and moderate drought, and mild shade alone or in combination with drought were treatments that promoted sexual reproduction.

Key words: Arthraxon hispidus, clonal growth, sexual reproduction, turfgrass, reproductive efficiency