| Summary: | 碩士 === 國立嘉義大學 === 林業研究所 === 90 === This study investigated the species of mycorrhizal fungi in the rhizosphere of Bhendi tree (Thespesia populnea (L.) Solander), Scaevola (Scaevola sericea Vahl.), and Pittosporum (Pittosporum pentandrum (Blanco) Merr.) stand in coastal forest in south-west Taiwan. Vesicular-arbuscular mycorrhizal fungi (VAMF) were screened, propagated, and inoculated onto roots and four salinities (0%, 1%, 2% and 3%) of Bhendi tree, Scaevola, and Pittosporum seedlings in order to study the effects of MF and salinities on growth and physiological characteristics of seedlings. This study investigated (1) effects of salinity on germination of seeds. (2) effects of stratification on sprout rate of seeds. (3) effects of vesicular-arbuscular mycorrhizal fungi on growth and salinity tolerance of seedlings.
The results showed that germination percentage of seeds of Bhendi tree, Scaevola, and Pittosporum decreased when salinities increased ; stratification can enhance germination percentage of seeds. In this study, two dominant VAMF, i.e., Acaulospora scrobiculata and Glomus mosseae were isolated. These VAMF were propagated and inoculated onto Bhendi tree, Scaevola, and Pittosporum seedlings. Seven months later, effects of these VAMF on growth and physiological characteristics of seedlings were measured and analyzed. The results indicated that A. scrobiculata could form vesicular-arbuscular mycorrhizas with roots of Bhendi tree and Scaevola seedlings, and that G. mosseae can form vesicular-arbuscular mycorrhizas with roots of Pittosporum seedlings, and there were significant enhancements in height growth, root collar diameter, dry weight, leaf area, N, P, and K element contents.
Seedlings were grown in different concentrations of salinity containing 0%, 1% ,2% and 3% NaCl for 90 days. The results showed that 3% salinity treatment caused death of inoculated Pittosporum seedlings; but did not cause death of Bhendi tree and Scaevola. However, it retarded growth of seedlings and caused obvious symptoms. As salinity increased, proline, Cl and Na element contents of plants, and Na element content of soil were increased. However, the height growth, dry matter weight, leaf area, chlorophyII content, water potential, photosynthetic rate and K, Ca and Mg element contents of plants were decreased. Experimental results further indicated that leaf succulence of Scaevola increased with increases in salinity. This process may maintain a reasonable amount of salt concentration. Photosynthesis characteristics were studied for seedlings grown under a variety of saline conditions. According to experimental results, the net photosynthetic rate were highest in 0% salinity. In addition, all net photosynthetic rate decreased when salinities increased. Ultrastructural study revealed that there were no significant differences among stomatal densities of seedlings cultured at 0%, 1% and 2% NaCl concentrations. However, the stomatal densities of seedling decreased significantly in 3% NaCl treatment. Cl and Na accumulated in various tissues of seedlings, Cl and Na content was decreased as follows: droped leaves and leaves > shoot and root. When old leaves aged and drop out, the salt accumulated in those left the seedlings.
This study demonstrated that A. scrobiculata and G. mosseae could stimulate the growth of Bhendi tree, Scaevola, and Pittosporum seedlings, and will be beneficial to the silvicultural practice of Bhendi tree, Scaevola, and Pittosporum in coastal plantation of Taiwan.
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