Emergência, crescimento inicial e características fotossintéticas de Licania tomentosa (Beth.) Fritsch (Chrysobalanaceae) sob diferentes ambientes de luminosidade

Abstract

The availability of light is one of the main factors limiting plant growth and development. Thus, this work aimed to evaluate the effect of light availability on the initial establishment and physiological characteristics of Licania tomentosa (Beth.) Fritsch. The study was conducted outside the Department of Biological Sciences. Elinsmar Adorno, from the UFRB Center for Agricultural, Environmental and Biological Sciences, located in Cruz das Almas, BA. For seedling emergence evaluation, 100 seeds were placed directly in eight washed sand trays and equally distributed in two treatments with light regime variations: shade (SO), under artificial shade imposed by shade screen, and full sun (PS) under direct solar radiation. The calculated variables were: emergency percentage (% E), emergency speed index (IVE), mean emergency time (TME) and mean emergency speed (VME). At the end of the emergency, after 76 days, the plants were transplanted to soil containing substrate and after 94 days the effect of light treatments, gas exchange, chlorophyll a fluorescence emission and chloroplast pigment content were evaluated. At the end of the experiment, 109 days after transplantation, growth parameters were again quantified to evaluate the biomass increment. The experiment was conducted in a completely randomized design (DIC), with two levels of light availability, with variable number of repetitions per treatmentt and the results were subjected to analysis of variance at 5% probability. The emergence of L. tomentosa seedlings showed no statistical difference between treatments. The plants grown in PS had the highest average leaf number, specific leaf mass (MFE), net assimilation rate (TAL), maximum photosynthetic capacity (Amax), dark respiration rate (Rd), compensation (Ic) and saturation (Is) irradiance, net CO2 assimilation rate (A), stomatal conductance (gs), transpiration (E) and carotenoid content. On the other hand, SO plants presented higher values of relative growth rate (TCR), minimum fluorescence (F0), maximum fluorescence (Fm), regulated dissipation yield (YNPQ), as well as total chlorophyll a, b, and totals, when compared with PS plants. The studied species presented alterations in the photosynthetic characteristics according to the light environment in which the plants were subjected, being able to survive exposed to direct solar radiation or shading. light dependent.