The influence of soil water deficit imposed during various developmental phases on physiological processes of tef (Eragrostis tef)

Physiological responses of tef (Eragrostis tef (Zucc.)) to water stress during establishment. vegetative, flag leaf-1 and grain filling developmental stages were Studied under glasshouse conditions in 2007 at Henfaes Research Centre, University of Wales, Bangor, UK using a "near-factorial" randomised complete block design. During each phenological phase plants were subjected to three levels of soil moisture tension viz., FC (-0.12 MPa), 50%FC (-1.06 MPa) and 25%FC (-1.51 MPa) until the completion of the specific phases and during the preceding and subsequent growth periods the stressed plants were irrigated to field capacity (FC). A maximum net CO(2) assimilation (12.15 mu mol m(-2) s(-1)) and transpiration (3.88 mmol m(-2) s(-1)) rates were recorded in the control treatment. Both levels of water stress during nag leaf-1 and grain filling development stages reduced these rates significantly. Severe water stress imposed during grain filling stage produced the lowest rates in both CO(2) assimilation (-2.80 mu mol m(-2) s(-1)) and transpiration (0.15 mmol m(-2) s(-1)). Response curves of CO(2) assimilation rates to PAR levels showed that initial photosynthetic efficiency (at light saturation point) of severely stressed tef was less (0.013 mu mol CO(2)/mu mol photons) than the corresponding efficiencies of other treatments (P < 0.001). The grain filling stage of tef was the most sensitive to water stress and severe water stress caused significant reduction in physiological performance of tef. The low yielding nature of tef could be associated with its low light use efficiency which perhaps related to its leaf size and orientation. Therefore, improving tef light use efficiency should be a national agenda to improve its yielding potential. (C) 2009 Elsevier B.V. All rights reserved.