Abstract
Lippia alba (Mill.) NE Br. ex Britton & P. Wilson is an important medicinal herb widely distributed in Latin America. However, the success of this crop depends on several biotic and abiotic environmental factors, being water availability the most limiting one. Therefore, the present paper aimed to investigate the responses of one tetraploid (tet) and two diploids (dip1 and dip2) genotypes of L. alba to drought stress by using irrigation suspension under 0 (control) or 15 (stressful factor) days. The physiological parameters water content, gas exchange, chlorophyll a fluorescence, photosynthetic pigments contents, and the qualitative profile of volatile organic compounds were evaluated by uni- and multivariate statistical analyses. Drought stress negatively affected the physiological processes in all L. alba specimens equally, regardless of the genotype. It was observed that photosynthesis was impaired due to stomatal limitation, which was triggered by low water availability. In contrast, the qualitative profile of volatile organic compounds was strongly determined by genotype without drought stress influence. Furthermore, gas exchange and chlorophyll a fluorescence were the most sensitive parameters to evaluate drought stress in L. alba. More specifically stomatal conductance is recommended to be evaluated in L. alba breeding programs focused on drought stress tolerance, given that its high contribution to photosynthesis regulation.
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