Plasticidade fenotípica em Glycine max e Brachiaria brizantha sob diferentes regimes de temperatura

Abstract

The environmental in which plants are subjected, and the resources necessary for its survival offers a series of restrictions on development imposed by variations in biotic and abiotic factors, mainly temperature. However, responses to environmental changes in agricultural production are variable between different crop species, especially with regard to differences between plants of C3 and C4 metabolism. The aim of this study was to compare the physiological responses of two tropical crop species with C3 and C4 photosynthetic metabolism grown in different temperature regimes, and verify their capacity for acclimatization. The species studied were: Glycine max (L.)Merr, cv. Codetec 202 (Fabaceae) of the cycle C3 and Brachiaria brizantha, cv. Marandú (Poaceae) of the C4 cycle. The plants were treated in a chamber type phytotron (Eletrolab, model EL 011) at temperature (day/night) of 20/15, 30/20 and 40/20°C. Measurements of the photosynthetic variables were extracted from curves A/Ci, curves A/PPFD, chlorophyll fluorescence, and growth variables. Data were subjected to analysis of variance (ANOVA, p<0.05) and means compared by Tukey test (p<0.05) and calculating the index of phenotypic plasticity (IPP). The results showed that under low temperature biomass losses were higher than under high temperature in both species, the same occurred in relation to membrane damage. On the other hand, the photosynthectic capacity of C3 species was more stable at different temperatures, whereas C4 species showed a significant increase at 40°C and a significant reduction at 20°C. In conclusion, the set of results indicated that low temperature caused greater damage to both species, particularly in the C4 species. Moreover, both species showed a greater capacity for acclimation to high temperature. In general, the C4 species showed a phenotypic plasticity comparable to the C3 species.