The water transportation within a clonal-fragments of Sasa kurilensis in different light environments: Can understory ramets function as water source to ramets in gaps?
2019
Tsunoda, Y. (Gifu University (Japan). The Unite Graduate School of Agricultural Science) | Ozawa, K. | Katoh, Y. | Mizunaga, H.
We observed diurnal changes in the sap flow rates of culms and rhizomes of Sasa kurilensis in different light environments to clarify: 1) the contribution of physiological integration to the water budget in ramets and 2) the time at which water transportation through rhizomes fulfills the function of physiological integration. We defined two culms through the rhizome as a clonal-fragment and measured the water flow in the culms and rhizome of a clonal-fragment using the stem heat balance method under different light conditions: the understory and in one small gap. We observed that the direction of water flow of intermediate rhizomes that were sandwiched in culms changed clearly during the daytime. This was not due to instantaneous phenomena such as noise. The flow direction was synchronized with the balance of the tug-of-war relationship of sap flow from both fragment ends in a small gap. Interestingly enough, the significant downward water flow from the culms to the rhizome was observed even in the daytime and in good weather, and the downward water flow was approximately 60% of the total daily flow of a culm in the understory. The water of clonal-fragments in the understory flowed from the fragment to the outside through rhizomes, and the water supply from the rhizomes to the clonal-fragment was 57.4-82.3% of the total transpiration (water flow from the clonal-fragment to the atmosphere) in a small gap. We suggest that ramets in small gaps and the understory play the roles of consumers and suppliers, respectively, and water supply through the rhizomes enables rapid and flexible water sharing among ramets to cover any daytime water shortage in the ramets.
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