During imbibition, seeds take an increasing amount of oxygen, causing the accumulation of reactive oxygen species (ROS) and a shift in the redox state. In that regard, the application of KNO 3 has been reported to increase antioxidant enzymes activity (superoxide dismutase (SOD), catalase (CAT), peroxidase (POX) and ascorbate oxidase (AOX)) in seedlings from different plant species. A role for nitrate reductase induction, related to N assimilation, and the antioxidative metabolism has also been described. In addition, exogenous KNO 3 has been reported to lead to an increase in the expression of genes involved in N and C metabolism, as well as in energy production. This in turn would indicate the role of NO in seed germination and seed dormancy breaking. This effect was reversed by the action of the nitric oxide (NO)-scavenger 2-4-carboxyphenyl-4, 4, 5, 5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO), suggesting an interplay between KNO 3 and NO metabolism. described that exogenous KNO 3 enhanced GA 4 content and reduced ABA levels, resulting in a decrease in the ABA/GAs ratio. In addition, the up-regulation of the CYP707A2 gene precedes the induction of the GA3ox2 gene, related to GA biosynthesis. Low nitrate concentration decreases ABA content, leading to the induction of the CYP707A2 gene, which encodes an ABA 8′-hydroxylase involved in ABA catabolism. Other authors reported that activation of ABA catabolism and GAs biosynthesis is required for seed germination. Gibberellins (GAs) are also important plant hormones for numerous physiological plant processes, including seed germination. KNO 3 has been reported to positively affect seed germination by modulating ABA metabolism or ABA signalling in developing seeds.

The effects of KNO 3 on plant hormones’ regulation are unclear, with most studies focusing on abscisic acid (ABA) levels. Other authors suggested that nitrates may enhance seed germination and early seedling growth due to the dual role of N as a plant essential element for growth and as a signalling molecule.

However, when the pea seeds were imbibed with KNO 3 (40 mM) for 24 h and then incubated in distilled water, seedling fresh weight was enhanced, whereas germination rate remained unchanged. Lincoln) displayed reduced germination and seedling growth when incubated for three days in the presence of 30 or 40 mM KNO 3, whereas 10 mM KNO 3 stimulated early seedling growth. Conversely, other authors reported that water-imbibed pea seeds ( Pisum sativum cv. Sea-Spray) were imbibed in 20–50 mM KNO 3 for three days. For example, improved seedling establishment was observed when seeds of Paspalum vaginatum (cv. The priming effect of KNO 3 seems to be dependent on the KNO 3 concentration and application method. However, the mechanism by which KNO 3 improves seed germination and seedling establishment remains unclear. Potassium nitrate (KNO 3) has been demonstrated to break seed dormancy, promote seed germination and enhance growth uniformity in a variety of plant species, including tomato, maize, Arabidopsis and pea. In this process, an interaction among KNO 3, antioxidant defences and ABA/GAs ratio is proposed. (4) Conclusions: Pea seed treatment with a low KNO 3 level promoted early seedling growth.

Low KNO 3 levels strongly increased GA 1 and decreased ABA in both seedlings and cotyledons, resulting in a decline in the ABA/GAs ratio. KNO 3 induced a progressive decline in ascorbate levels and reduced (GSH) and oxidised (GSSG) glutathione. Low KNO 3 levels maintained the activity of antioxidant enzymes, while high levels reduced the activity of H 2O 2-scavenging enzymes. KNO 3 treatment differentially affected the antioxidant defences. (3) Results: Low (0.25 mM) KNO 3 levels increased seedling water uptake and growth, whereas high (40 mM) levels decreased seedling growth. (2) Methods: We describe the effect of incubation of dry pea seeds with different KNO 3 concentration on water uptake kinetic, early seedling growth, antioxidant metabolism and hormone profile in pea seedlings. However, the KNO 3 effect seems to be dependent on plant species and treatment conditions. (1) Background: Seed treatment with potassium nitrate (KNO 3) has been associated with dormancy breaking, improved germination and enhanced seedling growth and uniformity in a variety of plant species.

Pea seedlings