Resumen

PAEZ, A et al. Growth, soluble carbohydrate and fatty acid concentrations of common purslane (Portulaca oleracea L.) grown under three irradiance levels. Rev. Fac. Agron. [online]. 2007, vol.24, n.4, pp.642-660. ISSN 0378-7818.

The annual herb purslane (Portulaca oleraceae L.), a widely-distributed C₄ species, was grown under different irradiances to determine the effect of light on plant growth, carbon allocation, soluble carbohydrate and fatty acid (particularly desaturated w3-fatty acid) concentrations of leaves. Seedlings were grown under three light regimes: full sun, partial shade (30% of full sun) and deep shade (10% of full sun). In full sun, rapid vegetative growth began after 13-15 d and flowering began one month after emergence, both of which were delayed by shade. At 3 wk after emergence, leaf area, leaf, stem, and root biomass were greatest in full sun. Root/shoot ratio decreased under lower irradiance, and leaf area ratio, specific leaf area, and leaf weight ratio increased in both deep and partial shade. At 6 wk, plants in full sun had a low proportion of its biomass in leaves (4%), and a high proportion in roots (50%), relative to the shade treatments, in which, stems and reproductive structures constituted a greater fraction of the total biomass. In deep shade, 46% of the total biomass was allocated to leaves. Additionally, lower irradiance reduced soluble carbohydrate concentrations of leaves to 18% of that in plants grown under full sun. Shade also tended to increase the concentrations of polar fraction fatty acids in leaves, including 18:3w3, and the poly-methyl branched alcohols and phytol. Whereas plants compensate for partial shade by reallocating carbon to leaf production, severe shade resulted in growth suppression and additional effects on carbohydrate and lipid metabolism.

Palabras clave : Portulaca oleracea; Purslane; irradiance; carbon allocation; carbohydrates; fatty acids.