Anatomical and physiological traits of Cattleya lundii (Rchb.f. & Warm.) under prolonged water stress

Abstract

Water deficit is one of the most limiting factors for plant growth and development, even for the Orchidaceae family, which is known for colonizing diverse environments with fluctuations in temperature, light, and water availability. During the study, Cattleya lundii (Rchb.f. & Warm.) Van den Berg was subjected to prolonged stress for 60 days, during which its anatomical aspects and the occurrence of cell wall components, photosynthetic activity, chloroplast pigments, and structural parameters of the bulbs and leaves were evaluated and compared to the control treatment. After the structural analyses, it was observed that the stressed plants showed a decrease in leaf area, accumulation of reserve substances in the pseudobulbs, and epidermal folding. The cell wall of the control treatment presented homogalacturonans (HGs) with high methylesterification, as well as extensins, which favor cell wall elasticity and volume increase. Plants under water deficit presented HGs with low methylesterification and (1→4)-β-d-galactans, which are associated with greater reinforcement of these structures, preventing their collapse and preparing for future rehydration. Regarding physiological aspects, statistical analyses indicated that plants under water deprivation presented low values in the analyzed photosynthetic parameters than the control treatment, indicating damage to the photosynthetic apparatus, mainly in photosystem II. Despite this, the pigments presented high values, indicating a possible compensation for this damage in order to balance the photosynthetic capacity. The results indicate that Cattleya lundii showed high tolerance to water deficit, and the anatomical and physiological modifications helped in adjusting to fluctuations in the water regime.