Uso da água por plantas híbridas ou convencionais de arroz irrigado

Abstract

RESUMO -Objetivou-se com este trabalho avaliar as características associadas à eficiência do uso da água em plantas de arroz irrigado, híbridas ou convencionais. O experimento foi instalado em casa de vegetação, em delineamento experimental de blocos casualizados em esquema fatorial 2 x 6, com quatro repetições. Os tratamentos constaram de uma planta de arroz da variedade BRS Pelota (convencional) ou Inov (híbrida) no centro da unidade experimental, que competia com 0, 1, 2, 3, 4 ou 5 plantas da variedade BRS Pelota na periferia da unidade experimental, de acordo com o tratamento. Aos 50 DAE, foram realizadas as avaliações de massa seca da parte aérea, condutância estomática de vapores de água, temperatura da folha e taxa de transpiração, sendo calculada ainda a eficiência do uso da água pela relação entre quantidade de CO 2 fixado pela fotossíntese e quantidade de água transpirada. Plantas da variedade híbrida foram superiores ou não diferiram das convencionais quanto à eficiência do uso da água.Palavras-chave: Oryza sativa, competição, fisiologia, hibridação.ABSTRACT -The objective of this work was to evaluate the characteristics associated to water use efficiency in hybrid or conventional rice plants. The trial was installed under greenhouse conditions, in a completely randomized block design and factorial scheme 2 x 6, with four replications. The treatments consisted of one hybrid (Inov) or conventional (BRS Pelota) rice plant at the center of the plot surrounded by 0, 1, 2, 3, 4, or 5 conventional (BRS Pelota) plants. Fifty days after emergence, shoot dry mass, stomatal conductance of water vapor, leaf temperature and transpiration rates were evaluated, as well as water use efficiency through the relation between the photosynthesis and transpiration rates. Hybrid rice plants were superior to, or did not differ from, the conventional plants in relation to water use efficiency.

Influência de Brachiaria brizantha nas características fisiológicas relacionadas a fotossíntese e uso eficiente da água em cana-de-açúcar

“…Corroborating with these results, there were no differences on the values of Gs among sugarcane varieties at a study conducted by Galon et al (2010) under field conditions. Differential responses of reduced GS in plants subjected to competition were observed for the rice crop, where one variety presented lower Gs in relation to the others evaluated at the same trial (Concenço et al, 2009). The GS is dependent on several factors, such as the number, size and diameter of stomatal opening, features dependent on endogenous and environmental factors (Brodribb & Holbrook, 2003).…”

“…Hence, the higher Ci observed for the variety RB72454 may be attributed to a possible lower photosynthetic activity which did not incorporate the CO 2 available at the substomatal leaf chamber. Concenço et al (2009) observed that the difference at Ci between rice varieties was most probably attributed to the distinct photosynthesis rate among varieties. Influence of Brachiaria brizantha in physiological characteristics ...…”

“…This impact was also observed for the photosynthetic activity, which may have led to reduced production of assimilates and deposition of dry matter. Increasing the density of weeds inside crops caused lower SDM accumulation in several crops, such as rice (Concenço et al 2009;Galon et al, 2010), soybean (Kuva et al, 2003) and maize (Vidal et al, 2004). However, some varieties show distinct competitive ability against weeds (Concenço et al, 2009;Galon et al, 2010), being less affected by the competition.…”

“…The most efficient use of water is directly related to the dynamics of stomatal opening, because as the plant absorbs CO 2 , water is lost through transpiration, with varying intensity depending on the gradient of potential between the sub-stomatal leaf chamber and the atmosphere around it (Concenço et al, 2009). It is estimated that for every 3,70 g m 2 of dry mass accumulated by Brachiaria decumbens there is an yield loss of around 1 t ha -1 for sugarcane (Kuva et al, 2003).…”

“…Whereas the competition with weeds cause physiological changes in crops, it is assumed that the physiological characteristics related to photosynthesis and water use efficiency can be indicators of the level of competition between these species and crops (Concenço et al, 2009;Galon et al, 2010). Therefore, this study aimed to evaluate the interference of populations of Brachiaria brizantha in traits related to photosynthetic activity and water use efficiency of sugarcane varieties RB72454, RB867515 and SP80-1816.…”