Jasmonic acid is required for tomato acclimation to multifactorial stress combination.

As a result of global warming and climate change, the number and intensity of weather events such as droughts, heat waves, and floods are increasing, resulting in major losses in crop yield worldwide. Combined with the accumulation of different pollutants, this situation is leading to a gradual increase in the complexity of environmental factors affecting plants. We recently used the term 'multifactorial stress combination' (MFSC) to describe the impact of three or more stressors occurring simultaneously or sequentially on plants. Here, we show that a MFSC of six different abiotic stressors (high light, heat, nitrogen deficiency, paraquat, cadmium, and salinity) has a negative impact on the growth, photosystem II function, and photosynthetic activity of mature tomato plants. We further reveal a negative correlation between proline accumulation and the increasing number of stress factors combined, suggesting that proline could have an adverse effect on plants during MFSC. Our findings further indicate that alterations in hormonal levels and stomatal responses are stress/stress combination-dependent, and that a tomato mutant deficient in jasmonic acid accumulation is more sensitive to high light and its combinations with salinity and/or paraquat. Taken together, our study reveals that the effects of MFSC on tomato plants are broad, that photosynthesis and proline accumulation are especially vulnerable to MFSC, and that jasmonic acid is required for tomato acclimation to MFSCs involving high light, salinity and paraquat.