| Summary: | 博士 === 國立臺灣大學 === 園藝學研究所 === 91 === To study the mass inoculum production of arbuscular mycorrhizal fungi, fungal samples were collected from Penghu, Kinmen, the north coast, and the east coast of Taiwan. In spring, blanket flower inoculated with arbuscular mycorrhizal fungi collected from Penghu (Glomus etunicatum Becker & Gerdemann, G.e) in sand+10% farm soil medium resulted in the best sporulation (2679/10 g). Cold storage spores at 4℃ showed higher germination rate than those stored at room temperature. Storage over six months could reduce the germination rate and the viability of spores.
The association of water melon (Citrullus lanatus (Thunb.) Matsum. et Nakai cv. Empire No. 2), cucumber (Cucumis sativus L. cv. Fountain) and angled loofah (Luffa acutangula L. Roxb. cv. Miriam) with arbuscular mycorrhizal fungi in plug system which commonly adopted by farmers were studied. The results showed mycorrhizal seedling grew well in low phosphorus and sterilized field soil or medium BVB #4. Based on the consideration of production managements and higher mycorrhizal infection rate, it was recommended that in 4.5 × 4.5 × 4 cm3 cellular size plug, with 1/3 organic manure or weekly applied with commercial fertilizer (Hyponex #4, 25-5-20) in 1000 dilution for four weeks could result in vigorous mycorrhizal cucurbits seedling. For three cucurbits crops, Glomus spp. were more suitable for application than Gigaspora spp..
The influence of arbuscular mycorrhizae on cucumber and butter head lettuce（Lactuca sativa L. cv. Red fire）under drought, temperature and salt stress were studied. The results showed that crops inoculated with mycorrhizal fungi grew better than non-mycorrhizal control (NM). In drought, cucumber inoculated with G.e and butter head lettuce inoculated with Glomus mix (G. mix) had higher yield production than NM. At 30/25℃, cucumber inoculated with G. mix had the highest growth and yield. However, butter head lettuce inoculated with G.e were able to produce the heaviest fresh and dry weights in all temperature treatment. Cucumber inoculated with G.e and butter head lettuce inoculated with G. mix showed to be the best tolerance to salt stress. Under environmental stress, the growth of cucumber and butter head lettuce were higher in Glomus spp. inoculated treatment than inoculated with Gigaspora spp..
The N, P, K, Ca, Mg, contents of mycorrhizal cucumber were higher than NM, but no significant difference in Na content under salt stress. The chlorophyll and protein contents, nitrate reductase and glutamine synthetase activitives of mycorrhizal cucumber were also higher than NM under salt stress. For mycorrhizal cucumber, the accumulation of proline was less than soluble carbohydrate. The higher soluble carbohydrate in mycorrhizal cucumber suggested a higher osmoregulating capacity of these plants.
Salt treatment resulted in an increase in abscisic acid (ABA) content, particularly to mycorrhizal cucumber seedlings. G. mix inoculation increased ABA content by 5.3-fold compared with NM plants. Under salt stress, ABA pretreatment could alleviate NM cucumber seedlings shoot fresh weight decrease, proline accumulation and water transpiration reduction than those of non-ABA pretreatment. This suggested that the degree of salt tolerance was likely related to ABA in NM cucumber seedlings. However, the effect of mycorrhizal cucumber seedlings on salt tolerance may not limited to ABA only.
Mycorrhizal fungi could enhance the nutrient uptake of host plant and resulted in the decrease of nitrate content . The vegetables included leaf lettuce (Hsing-Fong), leaf sweet potato, water convolvulus, endive and green onion. Combine the treatments of both mycorrhizal inoculation with phosphate treatments could significantly reduce nitrate content of lettuce and celery. For butter head lettuce, significant results were achieved by combing G.mix inoculation with the application of 5 g superphosphate in each 6 inches pot. For celery, significant results were achieved by combing G.e inoculation with the application of 6 g superphosphate in each 60 ×18 ×18 cm3 pot.
Effects of arbuscular mycorrhizal fungi and light intensity inside or outside of the plastic greenhouse on nitrate contents in butter head lettuce and water convolvulus (Ipomoea aquatica Forsk.) were studied. When growing inside the greenhouse , the chlorophyll content and nitrate reductase activity of butter head lettuce and water convolvulus decreased but nitrate content accumulated. Among all treatments, those mycorrhizal butter head lettuce and water convolvulus inoculated with G. mix or G.e contained the highest nitrate content. However, the nitrate content decreased to the lowest when they were cultivated outside the greenhouse. The nitrate content of two crops decreased along with the increase of time after growing outside the greenhouse. Butter head lettuce inoculated with G. mix and G.e decreased 50% of nitrate content rapidly after transferring to grow outside the greenhouse for just one day. Mycorrhizal water convolvulus also decreased 40% of nitrate content. But the decrease rate for NM comparatively was slow. No matter whether they were inoculated or not, the nitrate contents of two crops were lower than normal level after transferring to grow outside the greenhouse for one to four days.
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