| Summary: | 碩士 === 國立屏東科技大學 === 森林系所 === 99 === Abstract
Student ID: M9912005
Title of Thesis: Dynamics of the Photosynthetic Capacity with Leaf Age in Six Tree Species of Different Successional Status
Total Page: 76
Name of Institute: Department of Forestry, National Pingtung University of Science and Technology
Graduate Date: July 10, 2011 Degree Conferred: Master
Name of Student: Ming-Kai Huang Adviser: Dr. Yau-Lun Kuo
The Contents of Abstract in This Thesis:
The purpose of this study is to compare the lifetime pattern of photosynthetic capacity in leaves of six native tree species of different successional status. Leaf lifespan and photosynthetic capacity (Amax) of each species were monitored. The species used included two pioneer, Melanolepis multiglandulosa and Macaranga tanarius, one mid-successional species, Schefflera octophylla, and three late-successional species, Diospyros maritima, D. discolor, and Myristica cagayanensis. Two experimental procedures were conducted in this study. The first was monitoring the dynamics of photosynthetic capacity of leaves from a young age to abscission (continuous monitoring method); the second was to mark the newborn leaves along the same phyllotaxis, and measured the photosynthetic capacity of each leaf of different leaf ages when the first marked leaf became senesces (discontinuous monitoring method). The results from these two methods were compared, and suitable species for each method were recommended.
Results showed that among the six species, Mel. multiglandulosa had the shortest mean leaf lifespan of 95 d, following by 122 d of Mac. tanarius. The mean leaf lifespans of S. octophylla, D. maritima, and D. discolor were 243, 311, and 376 d, respectively. All the five species showed significant differences in mean leaf lifespan. Since no marked leaves died during monitoring period, therefore the leaf lifespan of Mir. cagayanensis is yet to be known. The Amax of Mel. multiglandulosa and Mac. tanarius were 27.3 and 25.4 μmol CO2 m-2s-1, respectively, and were significantly higher than S. octophylla, D. maritima, D. discolor, and Myr. cagayanensis (17.7, 9.8, 10.4, and 10.8 each). In addition, we found that in Mel. multiglandulosa, Mac. tanarius, D. maritima, and D. discolor the mean leaf lifespan was different among leaves born in different months: mean leaf lifespan of each leaf was negatively correlated with daily mean temperature during its lifetime, the higher the daily mean temperature the shorter the lifespan. However, the lifespan of S. octophylla leaf showed a bell-shape distribution pattern with regard to daily mean temperature during lifetime.
In Melanolepis multiglandulosa and Mac. tanarius the photosynthetic capacity had reached its maximum before full leaf expansion. Schefflera octophylla had almost reached its Amax when full leaf expansion occurred. As for D. maritima, D. discolor, and Myr. cagayanensis their Amax occurred sometimes after full leaf expansion. These results showed that there existed different developmental strategies in photosynthetic apparatus and leaf morphology among tree species from different successional status.
The differences in the results from the two methods (continuous vs. discontinuous) were compared using ten indexes. Result showed that in the short lived Mel. multiglandulosa and Mac. tanarius leaves the two methods had no significant differences, thus discontinuous method could be applied on these two species for acquiring the pattern of photosynthetic capacity during leaf lifespan in a short time. Adversely, in species with longer leaf lifespan, the results from the two methods were significantly different. This indicated that the discontinuous method would be inappropriate to acquiring such data.
The photosynthetic capacities in five species showed significant negative relationship with leaf lifespan. In D. maritima and D. discolor, however, the leaf lifespan was 65 d differed while the difference in Amax was small. This indicated that in these two species photosynthetic capacity and mean leaf lifespan were not significant related. As for different leaves on a single species, photosynthetic capacity was not significantly negatively correlated with leave lifespan. This result showed that different mechanisms existed to affect the above two functional traits.
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