Gaseous exchanges of corn and weeds under competition and water regimes

Abstract

Water deficits can alter vital physiological functions and negatively affect plant growth. These effects can be intensified by weeds competing for water available to crops. The objective of this study was to evaluate the effects of competition and temporary soil water deficit on the transpiration (E), stomatal conductance (gs) and photosynthetic rate (A) of corn, Urochloa decumbens, and Bidens pilosa L. The experimental design was in randomized blocks with eight repetitions. The treatments were arranged in a 5 x 2 factorial scheme, with the first factor corresponding to the species: corn + U. decumbens, corn + B. pilosa, and corn, U. decumbens, and B. pilosa without competition. The second factor was two water regimes: daily irrigation and water restriction, which corresponded to the suspension of irrigation from the beginning of the V3 stage of corn until the time when their stomata were completely closed. The species B. pilosa and U. decumbens worsened the negative effects on E, gs, and A of corn at different intensities under water restriction. The U. decumbens was more aggressive in relation to B. pilosa while coexisting with corn in both water regimes. The competition with corn affected the E and gs of U. decumbens in the two water regimes, but the A was altered under water deficit. On the other hand, the physiological components of B. pilosa were not affected by its coexistence with corn in the two water regimes.

WATER DEFICIT ON GROWTH AND PHYSIOLOGICAL INDICATORS OF Bidens pilosa L. AND Bidens subalternans DC.

“…The increase in the interval between irrigations, consequently water deficit, promoted a higher transpiratory rate mainly in B. pilosa plants, with an increase of approximately 30% in transpiration when the plants were irrigated every six days in relation to those irrigated daily (Figure 3C). Freitas et al (2020) observed a reduction in the transpiratory rate of B. pilosa after the fifth day of water deficit. However, the same authors did not find any difference in the transpiration of Urochloa decumbens when subjected to 5 days of water stress.…”

“…Therefore, the reduction in water availability causes a decrease in the water potential in the leaves of plants, resulting in loss of turgescence and reduction of stomatal conductance. Therefore, stomatal closure must have been the primary cause of the decrease in the transpiratory and photosynthetic rate under conditions of water deficit, since this reduction causes a decrease in CO 2 availability in the sub-static chambers (FREITAS et al, 2020).…”