S11 - Session O1 - Combined nitrogen and water stress affects morpho-physiological traits and alters endogenous hormone profile of tomato seedlings

Authors: Machado Joana, Joana Machado, Ana Patrícia Gonçalves, Marta W. Vasconcelos, Aurelio Gomez-Cadenas, Ep Heuvelink, Susana Carvalho *

In field conditions crops are often exposed to multiple abiotic stresses and recent research has been pointing out the importance of exploring plants' responses to combined stresses, due to possible interactions among them. Although nitrogen (N) and water (W) scarcity are among the most impactful parameters on plant growth and yield, little is known about the effects of combined N+W stress on morpho-physiological traits and on endogenous hormone concentration, being the scope of this study. Three-week-old 'Micro-Tom' seedlings were divided into four groups: control (CTR; 100%N+100%W), N deficit (50%N+100%W), W deficit (100%N+50%W) or combined stress (N+W; 50%N+50%W). Plants subjected to individual stresses had a significant decrease (25%) in total dry weight (TDW) and under combined stress TDW was even lower (53% decrease), as compared to CTR. Our results also showed that leaf area followed a similar pattern (i.e.18-28% decrease for individual stresses and 46% decrease in N+W stress), whereas the chlorophyll content and photosynthetic rate where only significantly reduced under N deficit (but to a higher degree when applied individually). Moreover, plants responded to stress changing their endogenous hormone profile. At root level, abscisic acid (ABA) concentration was only significantly affected by W deficit, leading to an increase in relation to CTR plants. Concerning salicylic acid (SA), jasmonic acid (JA) and indole-3-acid (IAA) concentration in the roots, W stress alone did not significantly affect none of them when compared to unstressed plants. Only when N deficit occurred (both independently or combined with W deficit) these hormones where significantly reduced in a similar way for both groups of plants. Overall, our data suggest that plants respond to N and W deficit in a different way and that the combination of both stresses is not always an additive effect at morpho-physiological or hormonal level.