碩士 / 國立屏東科技大學 / 森林系所 / 106 / Pittosporum pentandrum, Planchonella obovata and Aglaia formosana can grow on the west coast of the Hengchun Peninsula where is dry and rainless for up to six months every year, and they have the adaptability to arid environments. The purpose of this study is to find out their drought tolerance by determining leaf water potential at turgor loss point of these three types of trees. Can the forms of P. pentandrum, P. obovata, and A. formosana and their physiological performances when facing water shortage explain the reasons why these three types of tress can adapt to the weather in Hengchun? Field monitoring and water shut-off tests on potted plants in nursery gardens were conducted respectively. Field monitoring aimed to test and determine the changes of these three trees in predawn leaf water potential and leaf drought tolerance between the rainy season and the dry season on the coast of Shihchu. Water shut-off tests on potted plants in nursery gardens were divided into two parts. The first test determined the predawn water potential of these three potted plants with different leaf wilt states, and the decrease in chlorophyll fluorescence (Fv/Fm). The second test was to grow these three types of trees in a 60-cm deep tube container, and then cutting off the water or providing ample water was conducted respectively. During the water shut-off period, the physiological performances of plants were determined, and after the test, the numbers of roots of the plants with ample water supply were determined.
Results showed that the predawn water potential of P. pentandrum, P. obovata and A. formosana on the west coast of the Hengchun Peninsula in the later period of the dry season in 2017 was -0.36, -1.00 and -1.50 MPa respectively. A. formosana was influenced the most by the dry season, followed by P. obovata, while P. pentandrum did not encounter the water shortage. As to their leaf water potential at turgor loss point in the later period of the dry season, the results indicated that P. obovata and A. formosana had higher leaf drought tolerance, while that of P. pentandrum was lower. In the water shut-off tests on potted plants in nursery gardens, the stomatal conductance and transpiration rate of P. pentandrum that had not encountered water shortage were significantly higher than those of P. obovata and A. formosana. In addition, seedlings of P. pentandrum also had higher total leaf areas, which made its water consumption 3.8 times and 5.1 times higher than those of P. obovata and A. formosana respectively at the initial stage of cutting off water. As a result, P. pentandrum had faster consumption of water in the soil inside the container. During the 50 days of cutting off water, the photosynthesis rate, stomatal conductance and transpiration rate of P. pentandrum only remained below 20% at the initial stage of cutting off water, while the three physiological performances of P. obovata and A. formosana both remained over 40%. The period of cutting off water resulting in the zero photosynthesis rate for P. pentandrum, P. obovata and A. formosana was 72, 126 and 140 days respectively. This result showed that P. pentandrum suffering from earlier water shortage had serious physiological inhibition. After the water had been cut off for 108 days, water potential at turgor loss point of P. pentandrum, P. obovata and A. formosana was -2.66, -2.78 and -3.03 MPa respectively, which all showed high leaf drought tolerance. The predawn water potential of A. formosana with the zero photosynthesis rate was -8.30 MPa, which indicated that this type of tree had extremely high physiological drought tolerance. The potted seedlings of P. pentandrum with ample water supply had up to 412 roots at the 40 cm depth under the soil surface, which was obviously much higher than those of P. obovata (125) and A. formosana (181). Large quantities of root systems were advantageous to its continuous absorption of water in the soil. Results of this study showed that P. pentandrum, P. obovata and A. formosana all had very high drought tolerance, which could explain why they were adapted to grow on the coast of Shihchu.
| Identifer | oai:union.ndltd.org:TW/106NPUS5360003 |
| Date | January 2018 |
| Creators | Liu, Chen-Shi, 劉承熹 |
| Contributors | Kuo, Yau-Lun, 郭耀綸 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 87 |
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