Photosynthesis of Tropical Pasture Plants II. Temperature and Illuminance History

Abstract

Grasses and legumes were grown at two temperatures in controlled-environment rooms and at three illuminances (obtained by shading) in a glasshouse. Carbon dioxide and water vapour exchange of leaves were measured in an open gas analysis system.Net photosynthetic rates of grasses and legumes grown at 20°C and measured at 30°C were lower (and transfer resistances were concomitantly higher) than values for plants grown at 30°C, but almost complete acclimatization to the higher temperature occurred within 15 hr. Dark respiration rates varied with species and with illuminance prior to measurement, but were unaffected by growth temperature.Shading markedly affected the anatomy and the photosynthetic characteristics of both grass and legume leaves. Shaded leaves were thinner and contained fewer, smaller, and less densely packed cells than unshaded leaves. Light saturation point, light compensation point, and dark respiration rate declined as the level of shading increased, but the initial slope of the light response curve was unaffected. The lower net photosynthetic rate of shaded leaves was associated with increased stomatal and mesophyll resistances, and it is argued that the latter arose from higher carboxylation resistances. Net photosynthetic rate was positively related to leaf thickness, specific leaf weight, and the reciprocal of mesophyll resistance. These relationships and the relationship between net photosynthesis and chlorophyll content are discussed.

Photosynthesis of Tropical Pasture Plantsiv. Basis and Consequences of Differences Between Grasses and Legumes

“…Data on the effect of various environmental and physiological factors on transpiration ratio were calculated from published net photosynthetic rates (Ludlow and Wilson 1971a, 1971b, 1971c and associated (but unpublished) transpiration rates.…”

“…Mesophyll and carboxylation components of intracellular resistance (equation 1) were calculated from published (Ludlow and Wilson 1971a, 1971b, 1971c rates of net photosynthesis and resistances (measured at illuminances between 4000 and 1l,000 f.c., 300±5 (.tll-I CO2, and 30±0·I°C leaf temperature) using the method of Chartier (1970a). It was assumed that the rate of photorespiration was equal to the stimulation of net photosynthesis when the ambient oxygen concentration is reduced from 21 to 0·2% (oxygen effect), and that all the respiratory flux enters the intercellular spaces.…”

“…Previous papers (Ludlow and Wilson 1971a, 1971b, 1971c showed that the tropical pasture grasses which have the C4-dicarboxylic acid pathway of CO2 fixation (Hatch and Slack 1970) have higher rates of fixation than the tropical legumes which have the Calvin (or C3) pathway. The present paper is the last to discuss the data of that experimental work.…”

Composición florística, diversidad y ecología de humedales herbáceos emergentes en la planicie costera central de Veracruz, México

“…También forma parte de humedales en Sudamérica y tiene aplicaciones médicas (Al-Shamma et al, 1982). Vigna luteola, de origen africano, es una trepadora presente en humedales herbáceos, altamente palatable y productiva usada para forraje (Ludlow y Wilson, 1971;Sasser y Gosselink, 1984). Luziola peruviana pertenece a un pequeño género de gramíneas que habita ambientes acuáticos de poca profundidad, que se reproduce sexual y asexualmente, y sirve de alimento a fauna silvestre como los capibaras (Quintana et al, 1998), además se aprovecha como alimento para ganado (Pereira et al, 2003) y en algunos sitios se ha convertido en una plaga que se ha buscado controlar mediante carpas (Sponchiado y Schwarzbold, 2009).…”

Fotossíntese, reservas orgânicas e rebrota do capim-mombaça (Panicum maximum Jacq.)sob diferentes intensidades de desfolha do perfilho principal

“…sob Diferentes... neste trabalho correspondem aproximadamente a 57% da relatada para folhas de capim-sempre-verde (Panicum maximum) cultivado sob plena luminosidade (Ludlow & Wilson, 1971). Visto que a fotossíntese máxima da folha é proporcional à intensidade luminosa reinante durante seu desenvolvimento (Ludlow & Wilson, 1971;Woledge, 1971), as taxas ora relatadas refletiriam a condição de luminosidade subótima na casa de vegetação.…”