Effect of Temperature,Light and Water Stress on Caesalpinia spinose Kuntze Seed Germination

The effects of seed germination of Caesalpinia spinose Kuntze was studied by control experiments which were different temperature gradients,light and PEG-6000 simulations of water stress.The results showed that:(i) the suitable temperature range for seed germination was 15-30 ℃.Germination rate was above 90 %.Average rate of germination was less than 7 days.Average rate of germination took 2.77d at optimum temperature 25 ℃,and Tara seed finished germination in 5 days and the germination rate was over 99 %.In low temperature conditions,Tara seed germination was very difficult.The germination rates was only 32.5 % within one month at 5 ℃,but the germination rate could be 90.83 % after transferred to thermostat at 25 ℃ after 5 days.High temperature above 30 ℃ also was not suitable for seed germination.The germination rate was lower,embryo root was yellowed,and it was difficult for normal growth;(ii) the effect of light on Tara seed was not obvious.The light 12 hours every day or shading condition had better effect;(iii) Tara seed germination rate and average germination rate in PEG-6000 concentration 15 % following water stress had no significant changes.The germination rate could be above 87.5 %.When strengthening water stress,the germination rate sharply fell.When PEG-6000 percent was 20 %,the germination rate was 70 %.When PEG-6000 percent was 25 %,the germination rate was only 16 %.The seeds did not germinate in PEG-6000 30 %.Tara seeds could tolerate a certain level of water stress.The water potential at 25 % PEG-6000 could be the critical value for Tara seeds germination.