Water Stress and Clipping Management Effects on Guineagrass: I. Growth and Biomass Allocation

Abstract

AbstractGrowth and biomass allocation of grasses depend greatly on their management and water status. This study was conducted to determine the short‐term interacting effects of clipping height and frequency with water stress on growth and biomass allocation of guineagrass (Panicum maximum Jacq.). After seedling establishment, plants were clipped at four frequencies and three heights, followed by exposure to water stress. Some plants were reirrigated to determine recovery. Plants were harvested after the water stress and reirrigation periods. In response to water stress, plants clipped at greater heights experienced a greater reduction of leaf and culm biomass than plants clipped at lower heights. Root biomass of stressed plants increased linearly with increasing clipping height. Leaf area declined linearly in stressed plants and increased in unstressed plants as clipping height increased and frequency decreased. Leaf area ratio (LAR) and specific leaf weight (SLW) of unstressed plants varied little; for stressed plants, however, LAR decreased and SLW increased as clipping height increased and frequency decreased. In well‐watered plants, the root‐to‐shoot ratio (R/S) was lowest with higher clipping; in the stressed plants, R/S increased with increasing clipping heights. During rewatering, a height ✕ stress interaction for leaf and culm biomass and leaf area was due to a smaller recovery for higher‐clipped than for lower‐clipped plants. Water stress decreased leaf and culm biomass and leaf area, reducing LAR and increasing SLW. These effects were greater in plants cut to greater heights and less frequently. Water stress also enhanced root biomass, suggesting photosynthate migration toward the roots.