The effect of altered sink-source relations on photosynthetic traits and matter transport during the phase of reproductive growth in the annual herb <Emphasis Type="Italic">Chenopodium album</Emphasis> |
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Authors: | Y Yasumura |
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Institution: | (1) Graduate School of Life Sciences, Tohoku University, 6-3 Aoba, Aramaki, Sendai 980-8587, Japan;(2) Present address: Department of Plant Ecology, Forestry and Forest Products Research Institute, Tsukuba, Ibaraki 305-8687, Japan |
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Abstract: | Annual plants transport a large portion of carbohydrates and nitrogenous compounds from leaves to seeds during the phase of
reproductive growth. This study aimed to clarify how reproductive growth affects photosynthetic traits in leaves and matter
transport within the plant in the annual herb Chenopodium album L. Plants were grown in pots and either reproductive tissues or axillary leaves were removed at anthesis. Matter transport
was evaluated as temporal changes in dry mass (as a substitute of carbohydrates) and nitrogen content of aboveground organs:
leaves, axillary leaves, stems and reproductive tissues. Photosynthetic capacity (light-saturated photosynthetic rate under
ambient CO2 concentration), nitrogen, chlorophyll and soluble protein content were followed in the 20th leaf that was mature at the start of the experiment. Removal of reproductive tissues resulted in accumulation of dry mass
in leaves and axillary leaves, and accumulation of nitrogen in stem as nitrogen resorption from leaves and axillary leaves
proceeded with time. Removal of axillary leaves proportionally reduced dry mass and nitrogen allocation to reproductive tissues,
thus affecting the quantity but not quality of seeds. Removal treatments did not alter the time course of photosynthetic capacity,
nitrogen, chlorophyll or soluble protein content during senescence in the 20th leaf, but changed the photosynthetic capacity per unit of leaf nitrogen according to demand from reproductive tissues. Together,
the results indicate that reproductive tissues affected carbon and nitrogen economy separately. The amount of carbon was adjusted
in leaves through photosynthetic capacity and carbohydrate export from them, and the amount of nitrogen was adjusted by transport
from stem to reproductive tissues. The plant’s ability to independently regulate carbon and nitrogen economy should be important
in natural habitats where the plant carbon-nitrogen balance can easily be disturbed by external factors. |
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Keywords: | Additional" target="_blank">Additional leaf senescence nitrogen resorption photosynthetic nitrogen use efficiency soluble protein |
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