Effects Of Environmental Factors On Seed Germination And Seedling Growth Of The Wetland Plant Alnus Trabeculosa

Alnus trabeculosa Hand-Mazz.is the important one of Alnus distributing naturally in Central China, which is the constructive and pioneer species of wetland forests.A. trabeculosa not only regenerate in bare areas (secondary succession),but also fix nitrogen symbiotically, to promote community succession and protect the wetland environment. Study of seed germination and seedling growth of A.trabeculosa can provide the basis of conservation and reconstruction of damaged wetland vegetation. Therefore, in this thesis four environmental factors, namely, temperature, light intensity, ground water level and burial depth were investigated to research the effect of environmental factors on seed germination and seedling growth of A.trabeculosa. In addition, we also study effect of storage condition and storage duration on seeds germination rate of A. trabeculosa in order to find suitable storage method to maintain the seed vigor.Under the controllable laboratory conditions, six temperature gradients (5℃,10℃, 15℃,20℃,25℃and 30℃)were set to study the effect of temperatures gradients on seed germination, activities of SOD,CAT, and POD of A. trabeculosa.The results show that seeds could germinate in the temperature range of 15-30℃and the optimum temperature range was from 20℃to 30℃Under these optimum temperature ranges, the seed germination rate and germination index were the highest. As the temperature decreased, he germination rate and germination index decreased significantly. When the temperature declined to 10℃, the seed can only sprout, but not germinate absolutely. The activities of SOD, CAT and POD were highest at 25℃and the lowest activity in 15℃or 30℃.It could be concluded that seed germination of A. trabeculosa required a certain temperature range (15-30℃),25℃was the optimum temperature.Under the controllable laboratory conditions, high light, low light and continuous dark 3 light gradients were set to study the effect of different light intensity on seed germination and seeding growth of A. trabeculosa. The results showed that under the high light conditions, the seed germination and germination index of A. trabeculosa were the highest, but as the light intensity decreased, germination rate and germination index decreased. At the same time, light intensity had significant impact on the growth of seedlings. Seedlings in the dark condition had the maximum stem length and minimum root length;under high light conditions, although seedlings had the minimum stem length, the roots were growing best. It could be concluded that light could conduce seed germination and seedlings growth, even if it wasn’t necessary.In the study of effect of different burial depth on seed germination and seeding growth of A. trabeculosa, seven burial depth gradients (-0.2、0、0.2、0.4、0.6、0.8and 1.0cm) were set. The results show that the seed germination rate was highest at-0.2-0cm burial depth. Seeds did not germination when seeds were buried 1.0 cm deep. And when the burial depth was 0-0.2cm, the seedling growth conditions were best. As the burial depth increased, morphological traits index, seedling biomass and the root/shoot ratio of seedling decreased. Seeds floating in the water (-0.2cm) had the highest the germination rate, but the root could not be planted, died after germination. It could be concluded that 0cm burial depth could be more suitable for the seed germination or seedling growth. And seeds floating treatment did not inhibit germination.In the study of effect of different groundwater level on seed germination and seeding growth of A.trabeculosa, six ground water level gradients (2cm、0cm、-1cm、-2cm、-4cm、-6cm、-8cm and-10cm) were set. The results show that as the ground water level increased, the seed germination rate decreased significantly. The seed germination rate was highest at-1-0cm water level.When the water level was-10cm, the seed didn’t germinate. Similarly, when the water level was-2-0cm, the seedling grew best. With the decline in water level, morphological traits index and seedling biomass decreased, but the root/shoot ratio increased significantly. It could be concluded that-1-0cm water levels is suitable for seed germination, but the two conditions, lack or excess of water(2cm), would suppressed seed germination.Under greenhouse conditions, seeds were stored for two months under four conditions (moist-cold, submerged-cold, dry-cold, dry-warm) before germination. The results showed that A.trabeculosa showed significant increased in seed germination when stored in dry-warm treatments.And seeds stored in dry-cold had lowest germination rate, which had no significant difference with germination rates restored in moist-cold and submerged-cold.It could be concluded that the seed vigor may decrease in low temperature.In another treatment, seeds were stored in dry-cold and dry-warm, and germinated after 2 month,4 months,6 months and 8 months.There were no significant changes between the germination rates of 4 times stored in dry-cold.The increased storage time caused significantly decreased seed germination in dry-warm treatment, as time goes by, the seed germination rate showed a declining trend, the germination rate dropped to 0% after 8 months.It showed that that the best way for retaining seeds viability in short-term was dry-warm storage, and dry-cold for long-term storage.