Abstract
When plants are subjected to competition, their physiological behavior changes. To understand the developmental physiology of weeds will subsidize the development of cropping systems which favor the crops plants in detriment of weeds. The objective of this work was to evaluate the physiological behavior of different weed species, growing under intraspecific competition. Greenhouse experiment was conducted in randomized complete block design arranged in factorial scheme 4 × 5 with four replications. Factor A was the weed species [Urochloa plantaginea (Alexandrergrass), Bidens pilosa (hairy beggarticks), Ipomoea indivisa (morningglory) and Conyza bonariensis (hairy fleabane)], and factor B was the plant density of these species (20, 40, 60, 80 or 100 plants m-2). The following variables were evaluated: sub-stomatal CO2 concentration, photosynthesis rate, consumed CO2, stomatal conductance, transpiration rate, water use efficiency, plant height, shoot diameter, leaf area, and shoot dry biomass. Alexandergrass relies on the superior control of stomatal opening and high water use efficiency. Hairy beggarticks efficiency in competition lies on its ability to remove water from soil to levels when the other surrounding plant species would undergo stress. Morning glory and hairy fleabane did not present detectable particular features in the study, and their importance as weeds is probably tied to other survival abilities but superior competition. In conclusion, the weed species studied present distinct competitive strategies.
Highlights
From an agronomic point of view, plants can be divided into two groups: desired or undesired
Factor A represented the weed species (Urochloa plantaginea-Alexandergrass, Bidens pilosa-hairy beggarticks, Ipomoea indivisa-morningglory and Conyza bonariensis-hairy fleabane) and factor B was the density of these species (20, 40, 60, 80 or 100 plants m-2, corresponding to 1, 2, 3, 4 or 5 plants per pot)
Alexandergrass relies on high leaf area and growth rates, with superior control of stomatal opening and high water use efficiency
Summary
From an agronomic point of view, plants can be divided into two groups: desired or undesired. No specific plant species can be considered a weed, as this will depend on the place and time when this species is present in the field. Even a plant of economic interest, such as corn, can be considered harmful if it is growing within a soybean crop (Concenço, Aspiazu, Ferreira, Galon, & Silva, 2012). Are subjected to both adverse environmental conditions and competition. “competition between plants” essentially results in reduced performance of a particular plant species of importance, due to the shared use of a limited available resource (Gurevitch, Scheiner, & Fox, 2009). Competition may be interspecific when occurring between different species, and intraspecific when occurring between individuals of the same species (Radosevich, Holt, & Ghersa, 1997)
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