Ecofisiologia de duas espécies lenhosas da Caatinga ocorrentes em inselbergs.

Abstract

In Brazil, there is a shortage of specific data on the biogeography, floristic and mainly physiology of the inselberg plants mainly in the Northeast. The objective of this work was to evaluate the influence of seasonality on the physiology of Luetzelburgia auriculata and Capparis flexuosa occurring in inselbergs. The data readings were performed on the mountain of the Rajada, inselberg located between the highways RN 086 and the BR-427 in the Microregion of the Eastern Seridó in the county of Carnaúba dos Dantas / RN. The analyzed plants are in the upper third of the mountain, at an altitude of approximately 370 meters. The readings were performed from 10:00 a.m. to 12:00 p.m., at intervals of four months, March (rainy season), July (intermediate) and November (dry) of 2018. The variables evaluated were: photosynthesis rate assimilation (A), CO2 internal concentration (Ci), transpiration rate (E), stomatal conductance (Gs), leaf temperature (Tleaf) and air temperature (Tair). Based on these data the instantaneous water use efficiency (A / E), intrinsic water use efficiency (A / Gs) and instantaneous carboxylation efficiency (A / Ci) were calculated. Measurements were made in the middle third of the plants, in healthy leaves, not detached and completely expanded, using an IRGA portable analyzer model IR-Cor 6400 XTR. Statistical analysis was based on the completely randomized design - DIC, with measures repeated over time. There was a variation in the averages of photosynthesis rate (A), stomatal conductance (Gs), transpiration (E) and internal carbon concentration (Ci), when these were compared at different times during the year. The leaf and air temperatures between the species varied between 5% and 1% probability respectively, whereas between seasons varied 1% probability by the test F. Instantaneous and intrinsic efficiency of water use when compared in different periods, species tend to increase in the dry period. Chlorophyll A presented a difference between 5% and 1% probability species between rainy, intermediate and dry periods. The levels of chlorophyll B and total chlorophyll and the relationship between chlorophyll A and B varied at 1% probability between species and between periods. There was an increase in the vapor pressure deficit as the period of the year became drier. t is concluded that the species C. flexuosa and L. auriculata, optimize the production of reserves in the rainy season, through the high concentrations of CO2, when they arrive at the driest period the species tend to lower their ecophysiological activities, based on the instantaneous efficiencies and intrinsic to water use we conclude that the species studied potentiate the use of water in the driest periods of the year. The increase in leaf and air temperatures, as well as the variation of chlorophyll A and B contents in drier periods, contribute to a decrease in the physiological processes of C. flexuosa and L. auriculata, and, finally, an increase in the deficit of vapor pressure in the driest periods does not interfere with the transpiration of the species.