Effect of the Soil and Plant Water Potentials on the Dry Matter Production of Snap Beans¹

Abstract

The need for greater plant yields and more efficient use of water makes it essential that the relations between soil‐water content, soil‐water potential, transpiration rate, and plant response be made ever more quantitative. The dry matter production rate of snap beans (Phaseolus vulgaris L., var. Bush Blue Lake) growing under field conditions on a sandy soil is analyzed during a drying period. Measurements of plant‐ and soil‐water potentials, dry matter accumulation, and stomatal resistance were made as soil‐water was depleted, while the transpiration rates were obtained by a model for a loosely structured canopy. The transpiration and dry matter production rates decreased curvilinearly with soil‐water potential. When the soil‐water potential decreased from −0.28 to −0.40 bar, there was 47% reduction in the dry matter production rate. This is related to the turgor pressure‐operated stomatal mechanism. The adaxial stomatal resistances increased at leaf‐water potentials lower than −8 bars, which coincided with a rapid decrease in the dry matter production rate. It was found that stomatal closure due to water stress resulted in a greater reduction of growth rate than in transpiration.

Análise de crescimento de duas cultivares de feijoeiro sob irrigação, em plantio direto e preparo convencional

“…Assim, as diferenças na TAL entre tratamentos (Fig. 7) sugerem que o sistema PD proporcinou elevação da fotossíntese líquida, em função, principalmente, do aumento do índice de área foliar, implicando maior interceptação e fixação de energia luminosa por unidade de área foliar (Bergamaschi et al, 1988), com maior assimilação de C, aliado, provavelmente, à maior absorção de nutrientes (Millar & Gardner, 1972). A evolução da TAL com a idade da planta sugere diminuição progressiva desse parâmetro fisiológico ao longo dos diferentes estádios, evidenciando maiores valores durante o período vegetativo da cultura, com declínio mais acentuado, seguido de uma relativa constância da assimilação líquida na fase reprodutiva, com retomada de decréscimos sucessivos do final do estádio reprodutivo ao término do ciclo da cultura.…”

Comparative Water Relations of Phaseolus vulgaris L. and Phaseolus acutifolius Gray

“…However, it is extremely sensitive to drought, and significant yield reductions due to mild drought are common (4,12). A related species, Phaseolus acutifolius Gray, tepary bean, has been reported to produce extremely well with limited moisture (2,3,13,15,20,21 Leaf area during the drying cycle was determined nondestructively by measuring the length and width of the center leaflet of each trifoliolate leaf.…”

Effects of different irrigation regimes on the yield and yield components of dry bean (Phaseolus vulgaris)

“…Since bean plants have a shallow root system (Zaumeyer, 1954;Burman and Bohmont, 1961), they are more sensitive than deep-rooted plants to excessive amounts of water and show a better response to light irrigation at short intervals (Burman and Bohmont, 1961;Dubetz and Mahalle, 1969;Millar and Gardner, 1972;Robins and Domingo, 1956). The number of irrigations and the amount of water supplied on each occasion depend on the season, the soil type and depth, the organic matter in the soil and the tilt of the field surface (Mimms and Zaumeyer, 1947).…”