Water relations in two cultivars of Napier grass under variable water supply and temperature conditions

Napier grass ('Pennisetum purpureum' Schumach.) is the main fodder for the dairy industry in eastern and southern Africa as in many other tropical/subtropical regions of the world. Plant water relations were assessed for two cultivars of Napier grass; Local and Bana, the latter being an infertile hybrid between 'P. purpureum' and 'P. glaucum'. Plants were grown in a controlled environment at diurnal maximum temperatures of either 25 or 35°C to assess their tissue water relations in response to variable water supply (25, 50 or 100% field capacity) to mimic current and possible future climatic conditions in east Africa. At 25% watering and 25°C Local had higher midday relative water content (RWC) than Bana, but not at 50 or 100% field capacity, at which RWC was higher for Bana than for the Local. At the cooler 25°C, Bana attained a leaf water potential (LWP) minimum of -2.88 MPa at 25% watering, while Local had -2.27 MPa. At 100% watering and 35°C, Bana had higher RWC and LWP than Local at 25%. In a hotter environment, Bana appears to maintain higher water status than Local at 25% when soil is at field capacity while other watering responses appear similar for both cultivars.