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

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.

The concurrent impacts of drought and leaf harvesting on two traditional African vegetable non-timber forest product species

“…[ 38 , 53 ] and B . pilosa [ 54 , 55 ] have some level of drought tolerance and showed a significant difference in the species behavior in response to drought stress. Also, the resilience of both species differed depending on what plant characteristics were considered, although with some variations (especially for Amaranthus sp .)…”

“…According to De Freitas et al . [ 55 ], Bidens is able to reduce water loss through stomatal closure, hence lowering the transpiration rate. This mechanism allows Bidens to thrive under water scarce conditions.…”

“…Contrary to our results, De Freitas et al . [ 55 ] observed a reduction in the number of leaves per plant under water stress of 25% field capacity, as a mechanism to reduce water loss. However, the authors found no significant effect on leaf production.…”

“…In contrast, B. pilosa is drought tolerant under any level of drought stress. Previous studies elsewhere already emphasized the drought tolerance of B. pilosa under severe drought stress [54,55]. According to previous studies, Bidens species possess a great ability to easily exploit the soil resources (i.e.…”

“…water and nutrients), allowing them to compete with other species in harsh environmental conditions [59,60]. According to De Freitas et al [55], Bidens is able to reduce water loss through stomatal closure, hence lowering the transpiration rate. This mechanism allows Bidens to thrive under water scarce conditions.…”