Crescimento inicial do meloeiro frente às mudanças climáticas

Abstract

The future scenario of climate change, especially in the semi-arid region of northeastern Brazil, including the increase in temperature and CO2 concentration, reduction of water supply and desertification, causing salinization of water and soil, may have an impact on the melon crop management. Thus, the main goal is to evaluate the initial growth of melon crop in face of changes in CO2 concentration, temperature, salinity and irrigation depths in order to verify the impacts of climate change on culture, as well as to elucidate mechanisms of tolerance in order to assist in obtaining more productive materials. Two experiments were carried out at Embrapa Semiárido (Petrolina - PE) and the others experiments were conducted at Embrapa Agroindústria Tropical (Fortaleza - CE). Regarding the experiments in Petrolina, the first one was done in growth chambers under two different temperatures (37°C and 40°C), in which the design was entirely randomized with four replicates. In the second one, modified open top chambers (OTCs) were used in the field, with the following treatments: 1- Side plastic chamber plus CO2 addition (550 ppm); 2- Chamber with plastic and CO2 environment (360 ppm) and 3- Without plastic and ambient CO2 concentration (360 ppm). The experimental design was in blocks, with three replicates. In relation to the experiments in Fortaleza, two experiments were performed with interactions (temperature x irrigation levels and temperature x salinity) in protected environments and in split plots (2 x 5). Gaseous exchanges, growth variables and carbohydrate contents were measured for all experiments, growing yellow melon crop (Cv Goldex) until the flowering phase (initial growth). Regarding the results of the Petrolina experiments in low-radiation growth chambers, the gas exchanges were not altered with increasing temperature and the initial growth of the melon crop was moderately tolerant to high temperatures. The increase of CO2 in the OTCs, combined with the increase in temperature caused by plastic, caused a decrease in plant growth. Elevation of CO2 concentration resulted in an increase in transpiratory and photosynthetic rates of melon crop. Furthermore, under conditions of 550 ppm CO2 and average temperatures above 40°C, plants were negatively affected as to their growth. In relation to the interaction among environmental factors, the 80-90% ETc (59 to 66.5 mm) depths with the mean temperature of 31.4°C allowed for greater growth of the plants in the vegetative phase (up to 28 DAT). Regarding the salinity experiment, the best interaction for the melon growth in the vegetative phase (up to 21 DAT) was observed in the protected environment with lower temperature (30.4°C). In summary, it can be seen that salinity affected the melon crop more when compared to the damages caused by water availability. In relation to the average temperature of the environment, the plants were moderately tolerant when there was an increase of 0.8°C, combined with a reduction of up to 20% of the water availability. This, in turn, when salinity was applied, an increase of only 0.3°C was more deleterious, causing lower growth and consequently lower fruit production.