Survival strategies of Centrosema molle and C. macrocarpum in response to drought

Orlando Guenni, Eva Romero, Yajaira Guédez, Mercedes P. Macías, Diógenes Infante

Abstract


The response of a genotype each of C. molle and C. macrocarpum to drought (low soil moisture availability) was studied in a seasonally dry tropical environment throughout 3 consecutive years. Changes in soil water content, leaf water relations and gas exchange, chlorophyll fluorescence, forage yield and leaf area index (LAI) were compared in well-watered and droughted plots. Soil water depletion during the study occurred mostly at 0‒20 cm depth. Minimum values of leaf relative water content, water potential (ψl) and net photosynthesis in unwatered plants were within the ranges: 68 (C. molle) to 70% (C. macrocarpum); -1.6 (C. molle) to -0.9 MPa (C. macrocarpum); and 8 (C. molle) to 10 µmol/m2/s (C. macrocarpum), respectively. Leaf movements helped to avoid excessive solar radiation incidence, yet efficiency of chloroplast Photosystem II in stressed leaves of C. molle was negatively affected. Above-ground biomass and LAI were reduced only in C. macrocarpum (45‒50% reduction) as a result of moisture stress. Leaves of both species behaved as isohydric, though larger declines in ψl in C. molle may suggest a less effective control of water loss; this promoted more leaf senescence. Drought survival in these species depends on a combination of avoidance and tolerance strategies; the relative importance of both mechanisms depends on species and the duration and intensity of water deficit. Further studies with a higher number of accessions/ecotypes of each species are suggested in order to corroborate our findings.

Keywords: Acclimation, physiological response, soil transpirable water, tropical forage legumes, water stress.


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DOI: https://doi.org/10.17138/tgft(5)1-18

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