Weed Growth and Dry Matter Partition Under Water Restriction

Abstract

The capacity of a weed to adapt to the restriction of growth factors is directly related to its ability to compete for those resources with the cultivated species. An experiment was conducted to evaluate the effect of water restriction on the growth and biomass partitioning of four species of weeds. The experimental design used randomized blocks, with five replications. The treatments were arranged in a 4 x 2 factorial, with the first factor being the weed species (Waltheria indica, Crotalaria retusa, Cleome affinis and Commelina benghalensis) and the second, two water regimes: daily irrigation (Irr) and water restriction (WR). The number of leaves, leaf area, dry mass of the plant and its parts (root, stem and leaf), and the mass distribution among different organs (roots, leaves and stems) were determined. The water deficit in the soil increased the root dry matter for C. retusa, W. indica and C. benghalensis, however, it did not alter the mass of the stem of the weeds. C. retusa and W. indica suffered a reduction on the number of leaves, leaf area, dry matter of the leaves and the plant dry matter under water deficit. W. indica and C. retusa had a reduction on the percentage of biomass allocated to the leaves, and an increment on the percentage of the roots mass, while C. benghalensis and C. affinis had an increase only on the roots mass.

Competition between cowpea and weeds for water: Effect on plants growth

“…Such information was also verified by Lima et al (2016) when evaluating, in the greenhouse, the ecophysiological behavior of these same weeds under conditions of water deficit. In general, they verified a reduction of the growth and alteration of the dry mass of C. benghalensis and W. indica in conditions of temporary water deficit in the soil.…”

“…The irrigated treatment plants continued to receive daily irrigation as described, and the plants of the water deficit treatment had their irrigation totally suspended, so the stress was the result of the gradual exhaustion of the water of the soil, maintained until the rate of assimilation of CO 2 (A) of the cowpea plants at 09:00 hours, reached values close to zero, which occurred after 11 days of irrigation suspension, at which time irrigation was resumed. The CO 2 assimilation rate was measured using an infrared gas analyzer (IRGA, portable model LI-6400, LI-COR Biosciences), according to the methodology of Lima et al (2016). At 21 days of evaluation, when the CO 2 assimilation rate of the 3/7 plants submitted to the water deficit equaled those of the irrigated plants, the plants were harvested.…”

“…Some species, such as W. indica and Crotalaria retusa, have strategies that allow the maintenance of the stomatal opening and continue to make photosynthesis even with little availability of water, to the detriment of their water status, being considered investor plants and, such as C. benghalensis and Cleome affinis, when under moderate water deficit, close their stomata to maintain their water status as a way to delay dehydration, being known as conservative plants (Lima et al, 2016).…”

Coexistence of soybean plants and Urochloa spp. under glyphosate and water deficit effects

“…The competition of the forage plant with soybean was restricted by the use of the herbicide, thus avoiding the occurrence of deleterious effects of water deficit on the crop. The higher water extraction capacity of some weed species increases their chances of establishment in crop areas (Craine & Dybzinski, 2013) and may limit the water availability to the crop, affecting its growth and development by inhibiting photosynthesis (Lima et al, 2016).…”

“…The intensity of water deficit effects depends on the species and the adaptation mechanisms. More sensitive species compete less for water than more tolerant ones, which have a greater capacity to compete with the crop (Lima et al, 2016). Therefore, the adaptation capacity of the species to water deficit is determinant for the maintenance of the photosynthetic activity (Vivian et al, 2013).…”