Effect of Water Salinity on Seeds Germination of Sterile Oat (Avena sterilis) and Rigid Rye Grass (Lolium rigidum) at Constant or Alternating Temperatures

Sterile oat (Avena sterilis) and rigid rye grass (Lolium rigidum) are well known grasses in many parts of the world. They grow in grasslands and arable lands. Both are recorded as serious weeds of arable lands in many countries worldwide. Seeds germination of both species were tested at four levels of water salinity concentrations (0, 100, 300, 500 mM/L of NaCl) and five different temperatures (Constant at 8 C ° or alternating temperatures of; 8/16, 10/18, 6/14, 10/20 C0). Photoperiods regime of 8 hours darkness and 16 hours of light at the constant temperature was implemented. The same was followed with the alternating temperatures with 8 hours darkness at the lower temperature and 16 hours light with the higher temperature. A. sterilis seeds showed better germination with high significance of (˂ 00.1) than L. rigidum seeds at all tested treatments. The mean number of germinated seeds of A. sterilis was (6) out of (20) seeds /petri dish whereas, it was nearly (3) geminated seeds with L. rigidum. Both species secured the highest germination percentage at level of alternating temperatures of (10/20 C °) with 40% (mean number of germinated seeds was 8 out of 20 seeds / petri dish) for A. sterilis and 25% (5 out of 20 seeds / petri dish) for L. rigidum. Although A. sterilis seeds showed some germination (25%) at constant temperatures of (8 C°), L. rigidum seeds were less in favorite of this climatic condition expressing its response to alternating temperatures. Generally, A. sterilis seeds showed better germination responses than L. rigidum seeds at all different level of tested temperatures. Moreover, A. sterilis seeds resist water salinity as high as 100 mM of NaCl/L and showed almost 50 % germination especially at its favorite alternating temperature of (10/20 C °). L. rigidum seeds also showed some resistance to 100 mM/L of NaCl giving about 35 % germination. However, both species gave poor germination at higher levels of water salinity of 300 and 500 mM of NaCl/L concentrations. Results confirmed that both species seeds germination are in favorite of moderate alternating temperatures condition expressing some resistance to water salinity. This explains both species invasion and persistence in arable lands being reported a serious weedy plant species especially in a Mediterranean climate and subtropical conditions. In addition those results showed some of the two species seed biological aspects, which could contribute to a better control practice of the two species in arable lands.