Studies On Seed Dormancy And Seedling Physiological Characteristics Of Sorbus Alnifolia

The seed biological characteristics, seed dormancy mechanism, and the methods to break seed dormancy, growth law and photosynthetic character of 1-year old seedlings were studied in this paper. The results were showed as follows:1.The seeds of Sorbus alnifolia had dormancy phenomenon. The causes of seed dormancy included as following three aspects:1)The mechanical obstruct from seed coat: The seed coat of Sorbus alnifolia was formed from endotesta and exotesta. The ezotesta was hard and lignified. The germination percentage reached to 51.67% both in isolated embryo and seeds removed 1/2 cotyledon. The germination percentages of seeds with bare cotyle-dons and bare radicle reach to 18.33% and 20.00%respectively. The mechanical obstruct from seed coat was one cause of seed dormancy of Sorbus alnifolia.2)The permeable obstruct from seed coat: Permeability experiments showed that there was no water permeability obstacles from seed coat. The maximum of respiration rate of scarified seed was 44.366μL/g·min which was 5 times of intact seeds. The impermeability of air through the seed coat was another cause of the seed dormancy.3)Germination inhibitors existed: Each part of Sorbus alnifolia seed contained some germination inhibitors which had the inhibitory effects on the percentage germination and growth of radicule. The existence of inhibitors is the main cause of seed dormancy of Sorbus alnifolia.2.The best way to break dormancy is to soak seeds in water+Low temperature stratification 45d. Seeds treated by 75% H₂SO₄ for 5min can break dormancy of Sorbus alnifolia. Seeds treated by GA₃ or NaOH can not help to release seed dormancy.3.Factors that affect net photosynthetic rate were different in the early growth stage and fast-growing stage of Sorbus alnifolia seedling. The influence order showed that Cond>PAR>RH>T_r>T_a>C_a>C_i; PAR>T_a>T_r>Cond>C_i>RH>C_a respectively in the two periods. In addition, the low root activity and low chlorophyll contents were factors which effected the plant photosynthesis in the early growth stage.