ABSTRACT The effects of alternating and constant temperatures and light regimes, osmotic and salt stress and pH were tested on seed germination in four populations of Eryngium caeruleum. Laboratory experiments revealed that the four populations exhibited different responses to alternating temperature and light conditions. Alternating temperature and photoperiod had a greater positive effect on seed germination compared to complete darkness. The optimal constant temperature within 10 ºC to 15 ºC for seed germination of each population was determined in a light/dark photoperiod. Seed germination severely decreased under water stress and was completely inhibited at -0.8 MPa osmotic potential. Saline stress sharply decreased germination percentage. Germination was restricted by pH lower and higher than 5 and 8, respectively. The information obtained from this study helps to fill the gap of knowledge about seed germination requirements of E. caeruleum and enhance our understanding of this species distribution and its potential to develop in stressful and/or new habitats.

Shepherd's purse (Capsella bursa-pastoris) is a problematic weed in citrus orchards and crop fields in northern Iran. In a series of laboratory and greenhouse experiments, we evaluated the effects that treatment with gibberellic acid (GA3) and potassium nitrate (KNO3), as well as environmental factors, including temperature, the duration of pre-chilling (wet and dry), drought stress, salt stress, pH, and sowing depth, have on seed dormancy breaking and germination in C. bursa-pastoris. Treatment with GA3 strongly stimulated germination of C. bursa-pastoris in conditions of light/dark and continuous darkness. The germination rate was highest (40.08%) for seeds treated with 400 ppm of GA3 in the light/dark condition. Treatment with KNO3 did not significantly influence seed germination. Longer wet pre-chilling promoted germination and was more successful in seed dormancy breaking than was dry pre-chilling. Seed germination occurred at 10-30ºC and within a range of pH of 3-11. Drought and salt stress both strongly inhibited germination. Seedling emergence decreased in proportion to sowing depth. The rates of C. bursa-pastoris germination and seedling emergence were highest for seeds on the soil surface.

We investigated the effectiveness of Nitroxin inoculation on lead (Pb) and nutrient uptakes by little seed canary grass. The factors tested included inoculation (or not) with Nitroxin and different soil concentrations of Pb (0, 200, 400 and 800mgPbkg-1 soil). Increasing soil concentrations of Pb decreased stem, leaf and root dry weights. Shoot phosphorus concentrations increased in parallel with increasing soil Pb concentrations. Nitroxin inoculation did not alter the phosphorus concentration of the roots. The Pb translocation factor was >1 in inoculated treatments in the Pb soil concentration range of 200 to 400mgkg-1; the translocation factor for 800mgPbkg‑1 with no inoculation of Nitroxin was, however, <1. Our results indicated that the Pb bioaccumulation factor for little seed canary grass was <1, indicating that it is a Pb excluding plant.