Moderate shade attenuates water stress and promotes greater physiological plasticity quantified by multivariate plasticity index (MVPi) in Handroanthus serratifolius (Vahl) S. Grose

We evaluated the physiological and morphological traits that contribute to Handroanthus serratifolius (Vahl) S. Grose phenotypic plasticity in acclimation to light and water variations in a nursery setting. Our main hypothesis is that moderate shade acts as an attenuator of water stress, reducing evaporative demand; and that the magnitude of physiological plasticity surpasses morphological plasticity when quantified. Data analysis was conducted using a multivariate approach to investigate the relationships between environmental conditions and plant physiological and growth responses. The greatest plasticity occurred between high and medium light, without much interference from water variations. As light decreased, overall plasticity diminished, while physiological adjustments became more prominent. The species exhibits greater phenotypic plasticity, coordinated primarily by physiological adjustments in plants under moderate to high light conditions, prioritizing photosystem II efficiency, electron transport rate, water potential, and water use efficiency. Based on our results, we recommend moderate shade to high light conditions for producing robust seedlings. Full shade conditions should be avoided as they worsen the effects of drought, despite the seedlings’ acclimation for survival. These findings translate into practical recommendations for improving the conditions that should be implemented to produce premium-quality seedlings with better development and subsequent hardiness potential in the field. By manipulating light availability in nursery environments, producers can optimize seedling quality through the species’ natural phenotypic plasticity mechanisms, which directly contributes to successful planting results, reduced seedling stress and mortality rates in the field, reduced operational costs, and improved species management in large-scale production to meet program requirements.