Seed Priming with Spermine Improves Early Wheat Growth Under Nitrogen Deficiency

Nitrogen (N) is a macronutrient essential for plant growth and development; insufficient N availability has an extensive impact on the overall plant metabolism and productivity. Polyamines, short aliphatic amino-containing compounds naturally produced by living cells, have been widely reported to be beneficial for plant performance under several unfavorable conditions. In this work, the role of polyamine spermine (Spm) as a priming agent for wheat growing under N deficit was investigated. Wheat seeds were primed with 0.1 mM Spm for 3 h, germinated for 48 h, and then grown in N-sufficient or N-deficient media for 8 d. Spm treatment anticipated seed germination and, though priming with Spm did not result in any stimulatory effect on plants developed under an N-sufficient medium, under N limitation many of the studied traits improved compared with control plants. Under N deficit, wheat seedlings originated from Spm-primed seeds showed increased root length, developed the third leaf earlier, and maintained higher total N and protein contents and higher nitrate reductase (NR) and glutamine synthetase (GS) activities in their leaves, compared to control plants. Likewise, total amino acids increased in the roots of primed seedlings, and carbohydrates enhanced both in roots and leaves. Our findings indicate that seed priming with Spm promotes wheat germination and early seedling growth under N limitation, mainly by promoting root elongation and N allocation to the aerial part.