Light is one of the main factors of physical environment and it controls plant growth and development by interfering with photosynthesis, especially concerning CO₂ assimilation. Photosynthetic characteristics and growth of C3 epiphytic orchids Miltonia flavescens and Miltonia spectabilis var. moreliana were analyzed under four radiation regimens (25, 50 and 75 %of global radiation and full sunlight). Anatomical characterizations were performed on plants grown at 25 % shade. Artificial shading was obtained using different shading nylon nets. The highest values of lightsaturated photosynthetic, dark respiration, net photosynthetic and leaf transpiration rates, stomatal conductance and intercellular to atmospheric CO₂ concentration ratio were observed at full sunlight and 25 % shade. Moreover, both species allocated greater amount of leaf dry weight in those treatments. On the other hand, it was observed a greater investment in pseudobulb biomass in more shaded conditions (50 and 75 %), corroborating with the highest values of intrinsic water-use efficiency observed in those treatments. It was found a significant effect of shading on leaf area and specific leaf area. The anatomical features reflected strategies to save water. The phenotypic plasticity and principal component analysis suggested that the physiological traits were more responsive to light levels than the morphological traits. The results indicate that those species appear to be adapted to high irradiances conditions and are capable of adjusting, via morphophysiological changes, to light availability.
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.