Studies on seed germination and growth in weed species of rice field under salinity stress

An investigation was made to see the salt tolerance of 10 weed species of rice. Properly dried and treated
seeds of weed species were placed on 9 cm diameter petridishes lined with Whatman No. 1 filter paper under
6 salinity regimes, viz. 0 (control), 4, 8, 16, 24 and 32 dS m-1. The petri dishes were then kept in germinator
at 25±1.0oC and 12 hr light. The number of germinated seeds were recorded daily. The final germination
percentage, germination index (GI), seedling vigour index, mean germination time and time for 50% germination
were estimated. Root and shoot lengths of the weed seedlings were measured at 20 days after salt application
and relative growth values were calculated. Results revealed that salinity decreased final germination
percentage, seed of germination as measured by GI, and shoot and root length in all the species. Germination
of most of the weed seeds was completely arrested (0) at 32 dS m-1 salinity except in E. colona (12%) and
C. iria (13.9%). The species C. iria, E. colona, J. linifolia and E. crusgalli showed better germination (above
30%) upto 24 dS m-1 salinity level and were regarded as salt-tolerant weed species. J. linifolia, F. miliacea,
L. chinensis and O. sativa L. (weedy rice) were graded as moderately tolerant and S. zeylanica, S. grosus
and C. difformis were regarded as least tolerant weed species.