2007 Fiscal Year Final Research Report Summary
Elucidation of gas diffusion mechanisms in mangroves for adapting to high salinity and application of the mechanisms for developing afforestation methods
| Project/Area Number |
17380193
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Boundary agriculture
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| Research Institution | Osaka Prefecture University |
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Principal Investigator |
KITAYA Yoshiaki Osaka Prefecture University, Graduate School of Life and Environmental Sciences, Professor (60169886)
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| Co-Investigator(Kenkyū-buntansha) |
SHIBUYA Toshio Osaka Prefecture University, Graduate School of Life and Environmental Sciences, Assistant Professor (50316014)
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| Project Period (FY) |
2005 – 2007
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| Keywords | Manaroves / O_2 / Hypocotyls / Roots / Leaf conductance / Afforestation / Transpiration / Photosynthesis |
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| Research Abstract |
Hypocotyls of the seedlings can play an important role for early seedling growth. In the present study, we examined the function of oxygen supply from hypocotyls to roots. We determined photosynthetic activity of the hypocotyls of the seedlings, and O_2 concentrations and gas diffusion characteristics in the hypocotyls using young seedlings of Rhizophora mucronata, which is a dominant species in mangrove forests in Southeast Asia.
The gross photosynthetic rates of hypocotyls increased with an increase in light intensity and reached the maximum value of 0.4 μmolCO_2 m^<-2> s^<-1> at a PPFD of 300 μmol m^<-2> s^<-1>, which was 80% of the CO_2 release rate from the hypocotyls in the darkness. The O_2 concentrations in an inner tissue system of hypocotyls were lower than the atmospheric O_2 concentration and lower at the regions closer to roots. The O_2 concentrations in the hypocotyls were 20%, 11%, and 1% when exposed to the air in the light, submerged in the light, and submerged in the darkness, respectively. The longitudinal gas-diffusion rate in hypocotyls was about 10 nmol O_2 s^<-1> in the light regardless of submergence.
Extended submersion of hypocotyls under water and shading of hypocotyls suppressed the leaf conductance and retarded growth of young seedlings. In conclusion, the hypocotyls generate O_2 with photosynthetic action and could transport O_2 to the roots during daytime even when the hypocotyls were submerged under water at a high tide. This function would allow seedlings of mangroves such as Rhizophoraceae having well developed hypocotyls to grow under muddy anaerobic soil conditions in estuaries.
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