Dry matter allocation in Medicago arborea and Medicago citrina in response to drought and defoliation

Abstract

Soil water availability is one of the main factors determining plant growth and forage production. The effects of soil water deficit on the development of two woody Mediterranean Medicago species, M. arborea and M. citrina were studied. A field experiment was carried out in the University of the Balearic Islands (Spain), under irrigated and drought conditions on both non-defoliated plants (NDP) and defoliated plants (DP). Under drought, all studied parameters for NDP were affected by water stress in summer, though there were no significant differences between species for shoot biomass (B). However, M. citrina maintained significantly higher leaf biomass than M. arborea, which represents a great part of B. On the contrary, M. arborea plants suffered total leaf senescence in summer, and B was totally composed of woody parts. For DP, spring–autumn was a favourable period for plant growth and development, under both water regimes. In well irrigated M. citrina plants, and compared with M. arborea, the capacity of regrowth was higher, and leaf area was similar for NDP and for DP. During summer, the regrowth was sensitive to the extreme temperatures. In drought conditions, the capacity of regrowth was relatively favoured in spring but completely inhibited in summer for both species.