Influence of moisture stress on growth, dry matter yield and allocation, water use and water-use efficiency of four <i>Indigofera</i> species

Abstract

The effects of moisture stress were evaluated in four Indigofera species (I. amorphoides, I. arrecta, I. coerulea and I. vicioides) using a pot experiment under glasshouse conditions. The aim was to examine the influence of moisture-deficit stress on physiological attributes and performance of the four Indigofera species. Based on plant available water (PAW) levels, three moisture levels were applied (no stress or 70–100% PAW, 40–70% PAW and 10–40% PAW) as experimental treatments and imposed on each species in a randomised complete block design with four replications. Moisture stress significantly reduced (p < 0.05) the total leaf area of I. amorphoides at moderate levels and that of I. vicioides at the most severe moisture stress level. The relative growth rate was significantly reduced (p < 0.05) in I. amorphoides but not in I. arrecta, I. coerulea or I. vicioides plants subjected to moisturedeficit stress. The reduction in total dry matter yield was due to the effect of moisture stress in reducing both leaf area and leaf area ratio. Drought stress-tolerance indices were not different (p > 0.05) for I. arrecta or I. coerulea grown under no stress and moisture-deficit stress conditions. The root mass fractions of I. amorphoides and I. arrecta were substantially increased (p < 0.05) due to moisture stress. Water-use efficiency was low in I. amorphoides under water deficit conditions, while that of I. vicioides was higher under severe stress conditions compared to non-stress conditions. Transpiration efficiency was, however, higher at moderate moisture-deficit stress levels than under non-stressed or severely stressed plants. Generally, the species investigated exhibited significant variation in terms of physiological attributes and performance response to moisture-deficit stress. Indigofera amorphoides was relatively sensitive while I. vicioides was able to maintain unabated growth under water stress conditions. This is highly relevant to programmes aimed at identifying suitable species as a source of fodder for livestock exposed to long dry seasons and frequent drought phenomena.

Keywords: dry matter yield, growth, Indigofera, moisture stress

African Journal of Range & Forage Science 2007, 24(1): 25–34