Salicylic Acid Applied via Irrigation Enhances Young Carica papaya L. Plant Performance under Water Deficit

Generally, water deficit induces a negative impact on vegetative growth and physiological and biochemical processes in Carica papaya L. However, the effects of drought magnitude and duration may be dependent on the ability of the genotype to activate mechanisms of defense against the imposed stress. Thus, the purpose of this research was to investigate the effectiveness of adding salicylic acid (SA) to the root system via irrigation against water stress. To assess the morphological and physiological responses of papaya to drought stress, seedlings were exposed to a regulated deficit irrigation system combined with the addition of SA to their irrigation water for 44 days. Results showed that water shortage inhibited papaya growth through the reduction in functional leaf number (27%), fresh (13%) and dry weights (17%), and stem width (9%). Moreover, water scarcity significantly decreased stomatal conductance (48%) and chlorophyll content (21%) and increased proline production (31%). Nevertheless, the exogenous application of SA relieved the effects of water stress on these characteristics, yielding similar values to those from control plants. Therefore, these findings prove the effectiveness of SA applied via irrigation in alleviating papaya damage under water deficit by preserving growth, stomatal conductance, photosynthetic pigments, and proline levels.