Ontogeny modifies the effects of water stress on stomatal control, leaf area duration and biomass partitioning of Pennisetum glaucum

Abstract

Summary• Experiments are presented that test the relative importance, during ontogeny, of stomatal control and leaf area expansion to optimum seasonal water use in pearl millet ( Pennisetum glaucum ). These parameters play a key role in the compromise between plant growth and water saving under unpredictable conditions of semiarid environments.• The response of growth and water use of crops to successive 15 d drought periods was measured under field conditions in Niger (West Africa).• From emergence to anthesis, biomass partitioning to stems and panicles depended strongly on leaf area development. Water use was linearly related to green leaf area duration in well watered plots, but was reduced proportionally more than green leaf area in drought-affected plots. The relations of crop growth rate and transpiration efficiency to leaf area depended on ontogenetic changes in biomass partitioning.• In P. glaucum , stomata play a dominant role in reducing crop water use under preanthesis drought, although this control becomes negligible after anthesis because of ontogenetic decline in the range of stomatal conductance. The rate of leaf senescence after anthesis is not drought-dependent.

Unidades térmicas e produtividade em genótipos de milheto semeados em duas épocas

“…Conforme Payne (2000) e Winkel et al (2001), para a safrinha, plantio da seca, o BRS 1501, apesar de não diferir estatisticamente da produção de biomassa e de grãos do ENA 1, deverá apresentar maior estabilidade de produção, pois apresenta maior número de perfilhos, o que é desejável, pois se algum estresse impedir o desenvolvimento de um dos perfilhos, haverão outros para manter a produtividade.…”

“…Além disto, o milheto pode também ser usado na produção de forragem, no pastejo ou silagem (Netto, 1998), e na produção de grãos usados no fabrico de rações animais, em virtude do seu baixo custo e boa qualidade (Rodrigues et al, 2001). Pode, ainda, ser alternativa alimentar humana em áreas de baixa precipitação pluvial (Bidinger & Raju, 2000;Winkel et al, 2001), como o Nordeste. No Brasil, o milheto, considerado uma planta de dias curtos (Norman et al, 1995), tem sido semeado em duas épocas: no final do inverno/início da primavera e após a cultura de verão (safrinha) (Netto, 1998;Geraldo et al, 2002).…”

Precision Planting Patterns Effect on Growth, Photosynthetic Characteristics and Yield of Winter Wheat under Deficit Irrigation

“…The photosynthesis and yield of furrow was higher than of uniform row and wide-narrow row. Water supply conditions affect the wheat leaf extension and leaf stomatal opening and then affect the photosynthesis (Winkel et al, 2001). The yield of winter wheat increased with the increasing irrigation, but the amplification decreased.…”

Photosynthetic response of mountain grassland species to drought stress is affected by UV-induced accumulation of epidermal flavonols

“…Acclimation to UV radiation during an early plant development (a period of A max rise) can probably induce protective mechanisms against drought, whereas such UV effect is relatively minor in fully developed leaves (a period of A max decline). Also Winkel et al (2001) documented an important role of ontogeny in response of Pennisetum glaucum June 13 50.8 ± 1.2 52.4 ± 1.3 24.0 ± 1.8 20.9 ± 8.5…”