Plant growth-promoting bacteria as affected by N availability as a suitable strategy to enhance the nutritional composition of lamb's lettuce affected by global warming.

Abstract

Heat and nutritional stresses have a significantly effect on the accumulation of bioactive and other compounds harmful to human health, like nitrates, in green leafy vegetables like lamb's lettuce. Plant growth-promoting bacteria (PGPB) have shown to confer beneficial biochemical changes to various crops under different stresses. The hypothesis proposed here is that the combination of optimal N level (2.5Mm, 12mM or 20mM of N) with the inoculation of PGPB in plants exposed to heat shock (43°C) may be a good strategy to obtain healthier lamb's lettuce with a higher yield. Results showed that a dose of 20mMN can be considered as overfertilization. Moreover, the inoculation of plants fed with fertilizers with reduced N and under heat stress, resulted in higher productivity and content of sugars (60%), amino acids (94%), nitrogen (21%), and total phenolic compounds (30%), and a reduced content of nitrates (27%).