Seed longevity under different environmental conditions is considered as one of the most important factors in the spread and persistence of an exotic species. The Experiments were conducted to determine seed persistence in soil, effects of submergence in water, flooding of the soil, and high temperatures on germination and viability of spotted spurge (Chamaesyce maculata) and wild poinsettia (Euphorbia heterophylla) as two exotic species in different regions of Golestan province. Spotted spurge seeds buried at depth of 10 cm maintained their viability above 95% after a year, while wild poinsettia seeds were destroyed completely after exhuming the soil. Seeds of both species were unable to germinate under submergence, but 92% of the spotted spurge seeds remained viable under this condition for 14 d. No germination was observed after 9 weeks submersion. Submersion duration drastically affected seed germination of wild poinsettia, so that no germination occurred after 6 d submersion. Twelve days after flooding, spotted spurge emergence decreased by 57% compared to the control. Ten percentage of wild poinsettia seedlings emerged when flooding was kept up to 12 d after sowing, while control had 96% emergence. Germination of spotted spurge seeds subjected to 140 oC for 5 min was 5%. Viability of wild poinsettia seed was completely lost at 120 and 140 C for 5 min. These results suggest that spotted spurge is capable of forming persistent seedbank. Seeds of spotted spurge were partially tolerant to submersion in water, but wild poinsettia seed are susceptible to submergence. The burning of crop residue could also prevent augmenting the soil seed bank of both species.

The management of cultivation technology and fertilizer application may adjust adverse effects of abiotic stresses such as water deficit on agricultural products. Therefore, a field experiment was carried out on growth, yield, nutrient uptake and anatomical properties of maize under three water regimes (well-watered, moderate stress and severe stress as 25%, 50% and 75% soil moisture depletion), two cultivations methods (direct seeding and transplanting), and two Arbuscular Mycorrhizal Fungi (AMF) levels (inoculated with Glomus mosae and uninoculated). The results showed that in plants under moderate water stress, the AMF inoculation percent was significantly higher than those under well-watered and sever stress condition. Inoculation percent in direct seeding was lower than transplanting. Transplanting plants had higher biological and kernel yield compared to direct seeding plants. Water stress reduced the total chlorophyll (Chl) content. Transplanting had greater Chl content in comparison with direct seeding. In all irrigation regimes, transplanting significantly increased N content. In direct seeding, the highest P content was observed in moderate stress and uninoculated plants. Stomatal density increased under water stress, but stomatal size decreased. Plants under severe water stress showed increased stomatal density compared with well waterbed conditions. In addition, severe water stress enhanced the UCT compared to well-watered condition. This study suggests the use of transplanting with AMF application to cope with the adverse effects of severe water stress on maize.