@phdthesis{oai:sucra.repo.nii.ac.jp:00018696,
 author = {BARNUEVO ABNER PLAZA},
 month = {},
 note = {xiv, 93 p., Mangroves are trees and shrubs that inhabit the coastal areas in the tropical and subtropical countries. They are known to provide important ecosystem services that contribute to human wellbeing. But, despite of its functions and values, they are one of the valuable habitats that have suffered widespread habitat loss due to increasing population density and continuing economic development in the coastal areas. The continuous degradation of mangrove habitats has encouraged government and multilateral sectors to undertake rehabilitation initiatives to foster the recovery and biodiversity of these areas. However, some rehabilitation initiatives suffer high mortality because of incorrect species-site matching and failure to recognize the ecophysiology of mangrove species with the environmental stressors. Inundation, elevation gradient and salinity fluctuations are considered the major abiotic drivers that influence the survival, growth and distribution of mangroves. In extreme conditions, these environmental stressors trigger excessive generation of reactive oxygen species （ROS）, affecting mangrove physiology and homeostasis, leading to oxidative stress and mortality if the condition remains exacerbated. As a natural defense to quench the deleterious effects of ROS, mangroves have developed an antioxidant （AOX） system to scavenge the excessive ROS. This study investigated the effects of salinity, water depth and inundation on the growth, biochemical stress responses, and ecophysiology of Rhizophora stylosa in greenhouse microcosm experiments and field studies.
The field study was conducted in Olango and Banacon Islands, in the central part of the Philippines where R. stylosa plantations was established over 60 years ago. Transect line plot method was employed to assess the mangrove forest structure perpendicular to the shoreline. The leaves of R. stylosa were collected from natural and planted forests within the sampled transect line-plot. For every sampled tree, the light intensity and the pore water salinity was measured in situ and the elevation gradient was estimated based on mean water level at neap tide. The collected samples were immediately frozen with dry ice inside a thermal box and transported to the laboratory. On the other hand, for microcosm experiments, mature propagules of R. stylosa were collected in Olango Island and two experimental set up were conducted. In the first set up, the propagules were individually planted in seed bag and cultured in aquarium tanks filled with different salinity treatments: low （LS） - 0 ppt, moderate （MS）  - 20 ppt and high salinity （HS）  - 35 ppt. The seedlings were arranged on the top of a platform and irrigated with low water （LW, 3-5 cm）, mid-water （MW, 10-13 cm） and high water （HW, 30-33 cm）. The developments of the first leaves were monitored, and the average height, biomass and leaf tissues were measured and sampled at 5 and 10 months. In another set up, the seedlings were cultured at the low-water level in three different salinity treatments. After 15 months, the seedlings were subjected to inundation hydroperiod simulating the tidal cycle as semi-diurnal inundation （SDI）, diurnal inundation （DI） and permanent submersion （PS） for one week. These microcosms simulated emerged and inundated conditions, mimicking intertidal inundation that seedlings would experience. Leaf samples from field and experiments were analyzed for hydrogen peroxide （H2O2）, catalase （CAT）, ascorbate peroxidase （APX）, guaiacol peroxidase （POD）, pigments, carotenoids, Fv/Fm and proline. Statistical analyses were done using XLSTAT Premium.
The mangrove forest structure （density, species diversity, average height, girth size） showed a significant difference between the natural and planted forests. The planted forest had lower structural complexity than the reference natural forest. Even 60 years after the forest was created in Banacon Island, it still lacked the understory of young cohorts. While a forest has been created, it does not mimic a natural forest. Future mangrove restoration programs should consider planting several species and maintain sufficient spacing for growth in order to reproduce in the rehabilitated areas some of the key ecosystem characteristics of natural mangrove forests and to achieve the best outcome and functionality of the restored habitat. Results of the biochemical analyses showed that the H2O2 and AOX activities for samples collected at the higher elevation areas with rare inundation have significantly higher values compared with the samples collected at the inundated areas. On the other hand, the chlorophyll a and b for samples at the inundated areas showed an increasing with salinity, while those in higher elevation and rarely inundated areas showed a decreasing trend. The long-term negative effects of high H2O2 at the plant and community levels were manifested in the reduction of growth rate in plants cultured in the greenhouse and the reduction of height in the 30-year-old R. stylosa plantation.
The results of the greenhouse experiment showed that salinity significantly influenced the early growth and biomass production of R. stylosa. At 5 months, low salinity provided the optimum condition for relative growth rate （RGR）, while at 10 months, the optimum condition and higher RGR shifted towards the moderate salinity. Salinity also influenced the biomass allocation and partitioning as shown in the root/shoot ratio. At 5 months, the seedlings cultured in high salinity had higher allocation for root biomass while those cultured in low salinity had higher allocation for shoot biomass. At 10 months, the biomass allocations shifted, and the seedlings cultured in high salinity had higher allocation for shoot biomass while those in low salinity had higher allocation for root biomass. This temporal shift in salinity preference and optimum condition implies an adaptive morphological plasticity with salinity stress. On the other hand, the proline content of the leaves showed a significant increase for seedlings cultured in moderate and high salinity at 10 months compared with at 5 months. This increase in proline accumulation signifies physiological adaptations to saline conditions, which is consistent with the observed changes in growth and biomass production. Results of the biochemical analyses of leaf tissues showed that levels of ROS and AOX activities were significantly lower in the emerged condition than those in an inundated condition. Periodic inundation （SDI and DI） imposed a higher order of stress as indicated by ROS levels compared with the effect of salinity, while prolonged inundation （PS） caused sublethal damage as manifested by the chlorosis of the leaves in moderate and high salinity treatments. The chlorotic leaves developed relatively faster in high salinity （4 days after） than in moderate salinity （5 days after）; whereas in low salinity, chlorosis was not observed even at the end of the experimental period. The pigments （Chl a and b）, carotenoids and Fv/Fm showed a significant reduction relative to the inundation hydroperiod in all salinity treatments, and the PS showed the highest reduction. Inundation and salinity both significantly influenced the reduction, but the inundation was the most influential factor.
Extrapolating ecophysiology of R. stylosa, this species had low tolerance to inundation stress （high ROS and AOX, reduced pigments）. Translating this low tolerance to field conditions, in the frequently inundated areas （i.e. seafront mangroves fringes） that are subjected to longer inundation at spring tides, this species may suffer from oxidative stress, stunted growth and consequently low survival., Table of Contents・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・iv
List of Tables・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・vi
List of Figures・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・vii
List of Appendices・・・・・・・・・・・・・・・・・・・・・・・・・・・ix
Acknowledgements・・・・・・・・・・・・・・・・・・・・・・・・・・・x
Abstract・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・xi
Chapter I : INTRODUCTION・・・・・・・・・・・・・・・・・・・・・・1
1.1 General Introduction・・・・・・・・・・・・・・・・・・・・・・1
1.2 Statement of the Problem・・・・・・・・・・・・・・・・・・・・・3
1.3 Objectives of the Study・・・・・・・・・・・・・・・・・・・・・4
1.4 Significance of the Study・・・・・・・・・・・・・・・・・・・・・5
1.5 Scope and Limitations・・・・・・・・・・・・・・・・・・・・・5
Chapter II : REVIEW OF RELATED LITERATURE・・・・・・・・・・・・・・7
2.1 Mangrove basic biology and adaptations・・・・・・・・・・・・・・・7
2.2 Mangrove species distribution and coverage・・・・・・・・・・・・・8
2.3 Mangrove functions and values・・・・・・・・・・・・・・・・・・9
2.4 Environmental stressors and biochemical responses・・・・・・・・・10
2.5 Mangrove status and threats・・・・・・・・・・・・・・・・・・12
2.6 Lessons-learned from mangrove rehabilitations・・・・・・・・・・・・13
Chapter III : METHODOLOGY・・・・・・・・・・・・・・・・・・・・・・15
3.1 Part 1 - field work・・・・・・・・・・・・・・・・・・・・・・・15
3.1.1 Field sampling and mangrove forest assessment・・・・・・・・・・・15
3.1.2 Studied species and sampling of leaves and propagules・・・・・・・・16
3.2 Part 2 - green house culture and laboratory analyses・・・・・・・・・17
3.2.1 Greenhouse acclimatization and bagging・・・・・・・・・・・・・17
3.2.2 Experiment 1 - effects of salinity and water depths・・・・・・・・18
3.2.3 Experiment 2 - effects of salinity and inundation hydroperiod・・・・・19
3.2.4 Measurement of plant growth and biomass・・・・・・・・・・・・19
3.2.5 Extraction and determination of pigments and carotenoid・・・・・・20
3.2.6 Fv/Fm measurement・・・・・・・・・・・・・・・・・・・・・・20
3.2.7 Extraction and assay for H2O2, APX, CAT and POD・・・・・・・・20
3.2.8 Extraction and determination of proline・・・・・・・・・・・・・21
3.3 Data processing and statistical analyses・・・・・・・・・・・・・・22
Chapter IV : RESULTS・・・・・・・・・・・・・・・・・・・・・・・・・23
4.1 Experiment 1 - effects of salinity and water depths・・・・・・・・・・23
4.1.1 Propagule development, growth and biomass・・・・・・・・・・・23
4.1.2 Leaf proline・・・・・・・・・・・・・・・・・・・・・・・・・25
4.1.3 Pigments, Fv/Fm and biochemical stress responses in emerged
condition・・・・・・・・・・・・・・・・・・・・・・・・・・25
4.2 Experiment 2 - effects of salinity and inundation hydroperiod・・・・・・27
4.2.1 H2O2 and activities of antioxidants・・・・・・・・・・・・・・・・27
4.2.2 Pigments, carotenoids and Fv/Fm・・・・・・・・・・・・・・・・27
4.3 Integrating both the greenhouse experiments and the field data・・・・・28
Chapter V : DISCUSSION・・・・・・・・・・・・・・・・・・・・・・・30
5.1 Adaptive morpho-physiological plasticity as a respond to
salinity・・・・・・・・・・・・・・・・・・・・・・・・・・32
5.2 Do mangroves need salt?・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・34
5.3 Comparison of stress between emerged and submerged conditions・・・・・35
5.4 The relationship of H2O2 with antioxidants and pigments・・・・・・・・37
5.5 Translating the effects of oxidative stress to the whole plant and
community level・・・・・・・・・・・・・・・・・・・・・・39
5.6 Species-specific niche-width and implications for mangrove
rehabilitation・・・・・・・・・・・・・・・・・・・・・・・40
Chapter VI : CONCLUSION・・・・・・・・・・・・・・・・・・・・・・・43
Chapter VIII : REFERENCES・・・・・・・・・・・・・・・・・・・・・・・45
TABLES・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・56
FIGURES・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・64
APPENDICES・・・・・・・・・・・・・・・・・・・・・・・・・・・・91, 主指導教員 : 浅枝隆, text, application/pdf},
 school = {埼玉大学},
 title = {Growth and biochemical stress responses of Rhizophora stylosa Griff. to salinity, water depth and inundation},
 year = {2018},
 yomi = {バヌエボ アブナー プラザ}
}