Tolerância hídrica foliar de aniba rosiodora ducke

Abstract

The Amazon region has a great variety of species with economic potential, but predatory exploitation has significantly reduced populations of these species. Among the species, Aniba rosiodora Ducke (Lauraceae) stands out, with great economic, social, and environmental relevance in this region. Reforestation with A rosiodora faces some challenges, for example, the high mortality of seedlings in plantations during their initial establishment. The main hypotheses for high mortality are water stress and high irradiance stress, the latter hypothesis having been proven in previous studies. Thus, this study investigated the leaf tolerance to water stress of A. rosiodora seedlings. The study was conducted in the Soil and Chemistry Laboratory of the Center for Higher Studies of Itacoatiara, with one-year-old seedlings produced in the nursery of Simpatia Farm, in Itacoatiara (AM). The methodology of pressure-volume curves was used, where fifteen leaves from five seedlings were immersed in distilled water for 12 hours in a dark and isolated environment, until total hydration, to be measured the mass of the leaves on an analytical scale and the water potential using a pressure pump. Ten readings of pressure and volume were taken as the leaves dehydrated on the bench during increasing periods (05; 05; 10; 10; 15; 25; 40 minutes; 06; 12 hours until complete dehydration). After recording the values of pressure and volume in dehydration, the pressure-volume curve was adjusted to determine the values of osmotic potential at maximum turgor (Po), hydric potential at the point of loss of turgidity (ΨPPT) and leaf elasticity modulus (ε) and compare them to other forest species already studied. The values of ΨPPT and Po of A. rosiodora were on average -2.07 MPa and -1.79 MPa, respectively. These values were less negative and more distant from zero than most tropical humid biome tree species described in the literature. This finding indicates that A. rosiodora possesses leaf mechanisms to tolerate moderate to high levels of water stress. The mean value of ε was 14.50 Mpa, lower than most other species already described, meaning that the leaves are more elastic, therefore, more resistant to drought, since the higher the ε, the lower the elasticity. This research advances knowledge about the ecophysiology of A. rosiodora by demonstrating its leaf mechanisms of resistance to drought stress during the seedling stage. Therefore, it is presumed that water stress alone is not capable of causing seedling mortality, since the proven leaf resistance to wilting indicates the ability to maintain physiological processes that depend on turgor (stomatal opening and water uptake from the soil). Studying the limiting factors such as light and water in isolation or independently is not enough to identify the cause of the losses of the species during its establishment. Therefore, it is recommended that further studies be conducted to verify the interaction of these factors in different environments, to analyze the physiological mechanisms determining the initial establishment of A. rosiodora.