Abstract
ABSTRACT Stress caused by soil water deficit has been one of the main factors that inhibit plant growth. The knowledge of the factors related to the behavior of weed species under water stress conditions can contribute to the elaboration of effective control strategies. Two experiments were carried out to evaluate the effects of the degree and duration of water deficit on physiological and growth indicators of two weed species (Bidens pilosa L. and Bidens subalternans DC.). The stress degree was simulated by four soil moisture: 100, 75, 50, 25% of total soil capacity. The water deficit duration was evaluated by five intervals of water supply: 0, 1, 2, 3, 4, 5, and 6 days. The experiments were carried out in a randomized complete block design with six replicates. The evaluated variables were: the photosynthetic rate (A; μmol CO2 m-2), stomatal conductance (gs; μmol H2O m-2 s-1), transpiration (E; mmol H2O m-2 s-1), number of leaves per plant, and dry matter of the roots, stems, leaves, and total. The results showed that the species of B. pilosa and B. subalternans tolerate low water availability conditions. Low stomatal opening and loss of leaves are mechanisms that ensure the survival of Bidens plants to the water deficit. However, water stress close to 25% of field capacity caused the death of species. The B. subalternans had higher sensitivity to the water deficit, showing a lower dry matter of leaf, stem, and root than B. pilosa.
Highlights
Weeds cause direct and indirect damage to human activities such as problems in urban environments, highways, railways, and rural areas
The plants of Bidens pilosa and Bidens subalternans demonstrated less stomatal conductance, transpiratory rate, and photosynthetic rate under conditions of 25% of field capacity in comparison to the other water contents (Figure 1)
The lower stomatal conductance is a result of the lower stomate opening under water deficit conditions
Summary
Weeds cause direct and indirect damage to human activities such as problems in urban environments, highways, railways, and rural areas. The weeds can interfere with the yield of crops. The economic losses in agriculture due to weed interference vary 30 to 40%, but in some situations, the losses can reach 100% (LORENZI, 2008; SOUZA et al, 2020). In addition to density and spatial distribution, the ability to adapt to adverse environments is a feature that increases the importance of some weed species in agricultural fields (SILVA et al, 2011; RAFAIN et al, 2020). Weed species that survive stress conditions, either during a crop season or between two seasons, can gradually increase the density of the infestation over time
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