Regulation of the photosynthetic capacity of primary bean leaves by the red:far-red ratio and photosynthetic photon flux density of incident light

ROBERTO BARREIRO; JUAN J, GUIAMET; JOSE BELTRANO; EDGARDO R. MONTAIDI

PHYSIOLOGIA PLANTARUM

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 1992 vol. 85 p. 97 - 101

0031-9317

The main objective of the present work was to examine the effects of the red:far-red ratio (R:FR) prevailing during leaf development on the photosynthetic capacity of mature leaves. Plants of Phaseotus vulgaris L. cv. Balin de Albenga were grown from time of emergence in a controlled environment room, 25 ± 3*C, 12-h photoperiod, with different light treatments: a) high photosynthetic photon flux density (PPFD) = 800nmolm-^s-´ + high R:FR = 1.3; b) low PPFD = 300 [lmol m^^ s"^ + high R:FR = 1.3; c) high PPFD = 800 fimol m"^ s~´ -t- low R:FR = 0,7; d) low PPFD = 300 |xmol m"-s ´ + low R:FR = 0.7. With an R:FR ratio of 1.3, a decrease in irradiance during leaf growth reduced photosynthesis when measured at moderate to high PPFD; but when measured at low PPFD, leaves expanded under low irradiance actually had photosynthesis rates higher than those of leaves grown in high irradiance, A low R::FR ratio during development reduced the photosynthetic capacity of the leaves, ln leaves expanded under R:FR = 0,7 and high irradiance photosynthesis was reduced by 42 to 89%, depending on the PPFD at which measurements were made, whereas for leaves developed at R:FR = 0.7 and low irradiance photosynthesis decreased by 21 to 24%, compared to leaves under R:FR = 1.3 and similar irradiance. The reduced photosynthetie capacity under R:FR = 0.7 correlated with lower chlorophyll content on an area basis. As with photosynthesis, the decrease in chlorophyll was more pronounced in leaves under R:FR = 0.7 and high irradiance. In natural environments, leaves may experience low R:FR conditions temporarily during their development, and this may affect their future photosynthetic capacity in full sunlight.