Seed priming is a physiological seed enhancement method.
Hydro- or osmotic priming can advance germination under adequate moisture
conditions. During direct seeding on well-drained paddy and upland fields, rice
seeds occasionally encounter low soil moisture conditions. Under these
conditions, rice seeds need to undergo rapid germination and secure
emergence through improved water absorption capacity and seed bioactive. This
study aims to clarify the effects of seed hydropriming on germination and
seedling vigor in rice under different soil moisture conditions. The study employed three
hydration conditions such as priming, soaking, and control. The seeds to be
primed and soaked were submerged in tap water at 30℃ for 12 h.
For priming, the seeds were subsequently dried to attain their initial seed
weight, but the seeds for soaking were not dried before sowing, and the control
seeds were untreated. In addition, different soil moisture conditions, such as
3%, 6%, 8%, 11%, 15%, and 20%, were set. Therefore, emergence time shortened
with seed priming at 3%-11% soil moisture contents. In particular, at 8% soil
moisture content, priming and soaking decreased emergence time by
26.8 h and 21.7 h, respectively compared with that of the control. At 8%-15% soil moisture
contents, shoot elongation rate obtained with the priming seeds increased
>1.2 times compared with that obtained with the control and soaking seeds.
At >8% soil moisture content, shoot dry weight obtained with the priming
seeds increased >1.3 times compared with that obtained with the soaking seeds.
Furthermore, at declining soil moisture conditions, the increase in
root dry weight is promoted by seed priming compared with that in the control
seeds. These results suggest that increased root growth affects plant water
absorption under low soil moisture conditions due to priming. This study
demonstrates that seed priming facilitates rapid emergence and seedling vigor,
unless extremely dry or flooded soil moisture conditions are present at
seeding.