Caracteristicas morfo-fisiologicas dofeijoeiro (Phaseolus vulgaris L.) relaci onadas com a resistencia a seca

AUTOR(ES)
DATA DE PUBLICAÇÃO

1992

RESUMO

The study was conducted at the National Pice and Bean Research Center (CNPAF-EMBRAPA) experimental station Goianira GO during the months of May to August in the year 1987 and 1988. The objectives of the experiments conducted were to evaluate drought resistance mechanisms in bean cultivar BAT 477 Carioca; and RAB 96 all promising for planting during dry period to support breeding program directed for regions of water defficiency. These materiais were irrigated conventially up to 15-20 days after emergence whem these water treatment were applied: irrigated moderate stress and severe stress. These water regimes in the soil were maintained until haverst. The irrigated treatment received good water regime or soil water potential above ?O,035 MPA at 15 cm depth. The severe wa ter stress treatment practically did not receive water after sustation of conventational irrigation and moderate stress treatment received intermediate water regime. To characterize the effect of water defficiency on drought resistance mechanisms the following crop caracteristics were evaluated: grain yield and its components and during the flowering stage specific leaf weight leaf area index tops dry weight, number of nodes on principal culm and branchs linear root density water absosption efficiency of root, leaf water potential stomata difusive resistance, and canopy temperature, the last parameters were evaluated over the day. Cultivars BAT 477 and Carioca generally presented greater recovery capacity and maintenance of higher water potential at the end of daily solar radiation or its instant reduction. There was no significant diference of minimum leaf water potential neither between water regimes nor between each cultivar. Stomata difusive resistance reduced with increasing solar radiation. at lower rate in cultivar BAT 477 and Carioca, when subjected to water stress. Methodology used in canopy temperature evaluation did disdisi vat-S ~ but temperature difference was evident between olants subjéted to good water condition and water stress. Cultivars BAT 477 and Carioca presented lower reduction in leaf area index and lower increase index of specific weight This implies maintenance of carbohydrate sinthesis area and less resistance of flux at storage sites. This characteristic was more evident in cultivar Carioca. These cultivars presented higher linear root density in the lower soil depth; when compared to cultivar RAB 96. Furtner, it was observed that water absorption efficiency of root increased with soil depth independent of water deficiency levels or cultivars studied. It was superior in cultivars BAT 477 and Carioca; specially in lower depths. Finally, it was verified that cultivars BAT 477 and Carioca presented productivity number of pods per plant and 100 grains weight higher than RAB 96 when subjected to water stress This cultivar. However presented good behavior, in isolated experiments conducted durlng dry period, but did not presented drought resistance levels equal to cultivars BAT 477 and Carioca selected for this purpose. Based on these results it is recommended that a program of physiology/crop breeding with the objective to develop bean cultivars for regions where the possibility of drougth spell exist, including the study on the mechanisms to maintain water absorption root density and efficiency and reduction of water loss; high diffusive resistance of stomatas to water loss and adjustemennt of LAI. It will be interesting to monitorate the leaf water potential early in the morning and specific leaf weight. Finally we recommend use of cultivar BAT 477 to genetic breeding program for bean crop looking to obtain the cultivars for regions where occurence of long period of drought is common during normal cultivation period, because that cultivar economize water due to its stomata resistance. Cultivar Carioca is recommended for those programs looking to obtain the cultivars for the regions where drougth occurence for short duration is expected, such as central part of Brasil during tne rainy season. Cultivar BAT 477 is recommended for this program but its production potential under adequated irrigation is low as shown in this study probably due to its high diffusion resistance Df stomata on influx of CO2 as inferred by high stomata resistance to water loss during almost whole day. Even under irrigated conditions

ASSUNTO(S)

botanica feijão - aspectos fisiologicos aclimatação (plantas)

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