Abstract:
Rice (Oryza sativa L.) is a staple food widely cultivated as a lowland crop in Sri Lanka. Flooding
significantly impacts direct-seeded rice planting in many rice growing areas of Sri Lanka. This
study aimed to develop and evaluate various seed treatments to enhance crop performance and
withstand submergence stress during the early developmental stage of the crop. The experiment
followed a two factorial randomized complete block design (RCBD) with three replicates. Seed
dormancy was eliminated by subjecting the seeds to 50°C for 5 days. Healthy seeds having more
than 85% of germination percentage from three promising rice lines (BW-NP-14-7-5, N2B4, S2B7)
and three rice varieties (Ld 368, Ld 253, Bw 372) were coated with Calcium Oxide (CaO) (20:6),
Alginate (20:3), Sodium Lauryl Sulphate (SLS) (40:9) and primed with Calcium Chloride (CaCl2)
(20:3) on a dry weight basis (g). Untreated seeds served as control. Germinated seeds were
completely submerged under 1m water level for twelve days. Among all treatments seed treated
with CaCl2 and Alginate resulted in a shorter mean emergence time, higher emergence index, and
higher final emergence percentage. Significant interactions (p<0.005) between seed treatment
and variety indicated that submergence tolerance depends on both factors of the factorial
experiment. Survival percentage on the 14th day recovery period showed significant differences
(p<0.005), with the highest survival percentage exhibited by Ld 253 under Alginate treatment.
Rice varieties demonstrated varying responses to submergence stress, altering shoot and root
growth dynamics. Although, plant height did not significantly differ among the seed treatments,
shoot elongation rate post-desubmergence showed significant differences (p<0.005). Root
lengths were higher in all seed treatments compared to non-treated seeds under submergence
conditions. The observed phenomenon of reduced plant height and enhanced root length
resulting from seed treatments under submergence conditions suggests that the plants had tried
to tolerate submergence stress through the quiescence strategy. A better vigour index of the
seedlings in all rice lines and varieties except N2B4 was observed by CaCl2 and Alginate under
complete submergence. The results underscored the significance of CaCl2 and Alginate as
promising seed treatment agents to enhance submergence tolerance in rice.
