Crescimento e teor relativo de clorofila de duas cultivares de sorgo sacarino produzidas no semiárido

Abstract

The Sorghum (Sorghum bicolor L. Moench) is a plant native to Africa, has different types, presents itself as culture adapted to adverse environmental conditions. Sorghum type of sweet has agronomic and industrial advantages in the production of ethanol, such as: short cycle; possibility mechanization of the harvest and moist stem with directly fermentable sugars. The objective of this work was to evaluate the morphology of growth and the relative chlorophyll content of two cultivars (BRS 506 e BRS 511) of sweet sorghum (Sorghum bicolor L. Moench) produced in semiarid. The experiment was installed at the Experimental Farm Vale do Curu in municipality of Pentecost – CE, was performed between March to July 2014 rainy season in the region. The treatments evaluated consist of two cultivars (BRS 506 e BRS 511) and evaluation of growth on different days after sowing (45; 60; 75 e 90) with a randomized block design repeating four times in a split plot arrangement (2x4). For evaluations of the morphological variables measurements were made every 15 days for the following variables: plant height (HP), number of leaves (NL), leaf angle +3 (AL + 3), medium stalk diameter (DMS) and the relative chlorophyll index. Data obtained were submitted to normality and homogeneity of variance tests, nonparametric test Kruscal-Wallis (5%) for non-normal data, analysis of variance (ANOVA) with Tukey test (5%) to compare means and polynomial regression to analyze the growth times. The results for average foliar angulation were 40º to 45 days whereas the DAS 90 to leaves were positioned with an inclination of 88º. For height of plants differ only in the 45 and 90 DAS, but there was an increasing behavior for both cultivars showing a variation of 157.08 cm to 301.23 cm tall for ages 45 to 90 DAS, respectively. For chlorophyll A has found a reduction when comparing the age of 60 DAS (36.72 pcs. IRC) by the age of 90 DAS (30.39 pcs IRC). The total chlorophyll differ statistically when compared the ages of 60 and 90 DAS, being observed chlorophyll index values of 48.64 and 38.75, respectively. As BRS 506 cultivars and 511 show similar morphological pattern each other, reaching height of 3 meters at the ages of 75 and 90 DAS, when cultured under the conditions of this work (dryland). Both cultivars has increase of the leaf angle from 45 DAS, and stabilization of the height at 60 DAS.