Mecanismo fisiológicos de resposta a disponibilidade hídrica e suas relações com o crescimento e produtividade de cultivares de pimenteira-do-reino em ambiente amazônico.

Abstract

Black pepper is a globally valuable spice widely used as a condiment. Brazil is one of the world's largest producers of black pepper, with the states of Pará and Espírito Santo as major contributors to both plantings areas and production. Given the economic and social importance of black pepper to the Northeast of Pará coupled with the lack of such studies concerning the Amazon region, it is crucial to understand the behavior of this crop under different edaphoclimatic conditions, as well as the effects of water availability on its agronomic traits and the amount of water required for optimal growth and yield. Additionally, monitoring water use efficiency is pivotal to understanding the soil-plant-atmosphere system and choosing the best water management practice. The experiment was conducted at the Tropical Products Company of Castanhal Ltda (TROPOC) area, located in the municipality of Castanhal, PA. The experiment was set up in a randomized complete blocks design (RCBD), with split plots, arranged in a 5 x 2 factorial scheme, using 10 treatments and three replications. Each plot had 16 plants, in a double row, with a spacing of 4.0 x 2.2 x 2.2 m between plants. The treatments comprised five soil water tensions (15, 25, 35, 45, and 55 kPa) - as a limit to open and close irrigation system, and two black pepper cultivars (‘Cloned’ and ‘Uthirankotta’). The cultivars were previously characterized for leaf area, anatomy, gas exchange and water status. Subsequently, to examine treatment effects, gas exchanges, water potential, production, yield and water use efficiency were also evaluated. Regarding cultivars characterization, a significant difference in both anatomy parameters and gas exchanges was observed, with the ‘Cloned’ presenting a higher efficiency as compared to ‘Uthirankotta’. On the other hand, for variables corresponding to growth and water status, ‘Uthirankotta’ was more efficient than ‘Cloned’. In this sense, there was an interaction between factors of water potential in the soil and cultivars for the AN/E and predawn water potential. In addition, the stomatal conductance, internal carbon concentration, Ci/Ca ratio showed interaction between soil water tensions and the evaluation period. Transpiration significantly changed for soil water tensions, cultivars and evaluation period. Finally, the productive variables presented an interaction between both soil water tensions, as well as evaluation period and cultivars and evaluation period, except for black pepper production and yield, which was significant for soil water tensions, cultivars and evaluation period. ‘Uthirankotta’ showed the biggest production of both green and dry pepper (6.55 and 3.05 kg plant-1, respectively) within two years of the production cycle.