Polyamines as seed priming agents under nitrogen deficiency: a preliminary approach

RECALDE L; CABRERA A; GROPPA MD; BENAVIDES MP

CABA

Congreso; LVI SAIB Meeting ? XV SAMIGE Meeting. SAIB-SAMIGE Reunión Conjunta 2020; 2020

Wheat is one of the most important crops cultivated around the world. Nitrogen is one of the most important nutrients for plants, required in large quantities by crops, and it is commonly scarce in most arable lands. Seed germination and seedling establishment stages are highly susceptible to adverse environmental conditions, and could have a major impact on wheat yield. Among different strategies for exogenous growth regulators application, seed priming with different chemicals is one of the most relevant. Polyamines (PAs) are nitrogen-containing molecules essential for plant growth and development, and are also involved in stress tolerance. In this work, PAs were tested as priming agents against N deficit in wheat. Seeds were treated with H2O (C), 50 µM of Putrescine (Put), Spermidine (Spd) or Spermine (Spm) for 3h and then placed in plastic trays for germination during 48h. Seedlings were transferred to hydroponics and grown for 8d in a growth chamber, in a complete (N7), moderately (N1) or highly deficient (N0.1) nitrogen medium. Total leaf N was reduced to 50% in N0.1 medium respect to N7 in C, but 40% in Spd or Spm treated plants. Root growth was stimulated in N deficient medium and this effect was accentuated with PAs treatments. The three PAs enhanced 30% (average) root growth when plants were cultivated in N1 medium compared to the respective N7, whereas in C plants, this raise in elongation was about 15%. Spm treated plants showed an increase in root length of 45% comparing N0.1 with N7, whereas this increase was 29% in C plants. Spm also slightly positively affected leaf growth. Nitrate reductase activity was increased by Spm (30% in N7 and 45% in N1) when compared to C, but remained almost undetectable when seedlings grew in N0.1, both in C and Spm-treated plants. Total nitrates and total ammonium contents were lower in N1 and N0.1 compared to N7 medium with all treatments, but they were even lower with PA treated plants. Total protein concentration decreased from N7 to N0.1. While in leaves there were no differences between C and Spm treated plants, in roots protein content were higher in Spm treated plant compared to C in both N conditions. Total sugars were reduced in roots by the three PAs, both in N7 and N0.1, compared to C, but their levels were increased 70% (on average) in leaves by priming treatments in N0.1 medium, compared to C. At time 0 of treatment (48h of germination after priming), superoxide anion and H2O2 levels were higher in Spm treated roots compared to C. At day 8 of growth, both radical species were increased to a similar extent in Spm or C treatments, either in N7 or N1 medium. There were no differences in nitric oxide levels. These results suggest preliminarily that priming with PAs, especially Spm, could be a plausible strategy to favor seed germination and post-germinative root elongation preparing seedlings for survival in deficient N soi