Morfologia de cultivares diploide e tetraploide de azevém em diferentes condições hídricas do solo

Abstract

The species Lolium multiflorum Lam., Also known as ryegrass, is an annual or biennial grass. It perfectly expresses its productive potential in the Southern Region of Brazil, forming dense populations, completely covering the soil where it is found. They can be implanted in areas for livestock, being used for nutrient cycling, hay, grazing, seed production and other purposes. Within the ryegrass species cultivars with different genetic loads, such as diploid (2n) and tetraploid (4n) cultivars occur. Because it is a plant with a rustic character, it adapts to various types of soil, and can be found or cultivated in areas of both native land and in upland or lowland (várzea) areas where irrigated rice is cultivated. The diversity of environments to which the ryegrass is found necessitates the study of their characterization to understand the adaptation process of this species in environments with different amounts of water in the soil. The objective of this work was to understand the structural (phenotypic) behavior and morphoanatomic alterations of ryegrass plants submitted to two soil moisture conditions, 50 and 100% soil water retention capacity (CRA). The experiment was carried out and developed in the agricultural year 2014/15 in the city of Santa Maria, RS, under greenhouse conditions. The water retention capacity of the soil was determined by drying the soil for uniformity and after successive waterlogging was carried out until there was water runoff in the basal holes of the pot. Two cultivars of ryegrass, one diploid (La Estanzuela 284) and another tetraploid (Winter Star) were used, with five seeds per pot being grown, with twenty pots with diploid seeds submitted to 50% of soil water retention capacity (CRA ) And 20 pots for cultivating diploid, 100% of CRA, the same was done for the tetraploid cultivar. In the V3 development stage, when the plants had three fully developed leaves, the thinning of the plants was done and only one plant per pot was left. In the V4 stage, the plants were submitted to the different amounts of water in the soil and during their development the anatomical-morphological behavior was evaluated, after the final results of the morphological evaluations, the quantitative morphological variables were submitted to the Genes program that generated results for divergence And genetic dissimilarity among cultivars. The results obtained in the present work show that, for the cultivar diploid (LE 284), a greater number of quantitative variables evaluated underwent changes when the cultivar was submitted to 50% of the CRA, when compared to the cultivar submitted to 100% of CRA . When the tetraploid cultivar (Winter Star) was submitted to 50% of the CRA, there were few modifications in the evaluated variables when compared to the cultivar submitted to 100% of the CRA. With these results it is possible to say that the diploid cultivar suffers more influence when submitted to the smaller quantity of water during the cycle of the culture. As for the genetic similarity of the cultivars, it is possible to conclude from the Mahalanobis distance that the lowest distance found between the tetraploids 50% and 100% of the CRA indicates that there is a genetic similarity between the cultivars and the greater distance shows that the similarity is low, By the diploid and tetraploid cultivars 50% of the CRA. Anatomically the work shows that differences between cultivars were observed, in which the diploid cultivar in 50% of the CRA and 100% of the CRA showed a higher formation of aerenchyma in the stem when compared to the tetraploid cultivar at 50% of the CRA and 100% of CRA. For root as the amount of water in the soil is increased in 100% of the CRA, some cells of the cortex begin to disintegrate and to form the aeration systems, the aerenchyma.