EFFECTS OF FLOODING ON SEVEN SPECIES OF TROPICAL PASTURE LEGUMES

Abstract

Seven tropical pasture legume species were grown in pots inside the glasshouse. At the start of flowering stage, plants were continuously flooded to 5 cm above the soil surface for 10 and 21 days. Dry weights of shoots, roots and nodules of the flooded plants were compared to the corresponding unflooded plants after a recovery period of 7 days. Macroptilium lathyroides exhibited superior tolerance to flooding while Cassia rotundifolia and Vigna parkeri showed very poor tolerance.
Root growth was more affected by flooding than shoot growth. Nodulation was reduced in all species except in M. lathyroides. The adaptation of M. lathyroides, Desmodium heterophyllum, Lotononis bainesii and Trifolium semipilosum to flooding was related to the rapid production of adventitious roots from the immersed stems and branches and to the rapid nodulation of these adventitious roots and the original roots.
High stomatal conductance was maintained in flood-tolerant species with increased duration of flooding while high leaf diffusive resistance was common in species intolerant to flooding.