Componentes morfofisiológicos em cana-de-açúcar submetida a diferentes regimes hídricos

Abstract

The sugar cane (Saccharum spp. L.) is one of the most important crops in Brazil, being used, primarily, to obtain sugar and alcohol. The availability of water in the soil for the plant is one of the major factors in obtaining high productivity and better quality products. In places where there is water deficiency, there is significant decrease in the production of sucrose. The aim of this work was to study the response of morpho physiological indicators in varieties of sugarcane under different water regimes in three production cycles. The experiment was conducted at the UNIMONTES campus, in the city of Janaúba, Minas Gerais. State, between the years 2012 to 2014. They were used three varieties of sugarcane: SP80-1842, SP79-1011 e RB86-7515, and three water regimes: 80 to 100% of field capacity (water comfort), 40 to 60% of the field capacity (severe water stress) and progressive drying (without irrigation). The plants were arranged in the field, in order to combine six treatments, with four replicates. In the years of 2013 to 2014 (experiment I), they were evaluated and compared the moisture levels of comfort and progressive desiccation. In the years of 2012 to 2014 (experiment II), were compared the moisture levels of comfort and severe water stress. For the years of 2013 to 2014, reviews of physiological characteristics were made, which are: coil and leaf drying, maximum quantum efficiency of photosystem II, SPAD index, percentage of water and specific leaf area. For 2012 to 2014, besides the features mentioned above, with the exception of leaf rolling and leaf drying, they were also evaluated the tiller number, height and diameter of the main stem. To the data obtained, it was performed a descriptive analysis for the three crop cycles, since the evaluations were conducted in different times and cycles (cycle of plant cane and two ratoon cane cycles). The results showed that for the first experiment, the responses to treatment occurred more rapidly for the year 2013 than in 2014, with fluorescence and the leaf symptoms that stood out. This can be explained by the availability of soil water to plants in 2013 was lower due to the experiment being conducted at different times of the annual season of 2014 (August to September in 2013 and April to May in 2014). The varieties showed similar behavior when compared to each other, and differences were only noted between the years of assessments. In the second experiment, comparing the years, the 2012 season showed better results in most of the variables analyzed. Fv/Fm were the best physiological characteristics that proved indicative of the characterization of the varieties as the behavior in different water regimes.