九州森林学会発表大会

401	Relative contribution of cotyledon nutrient reserves to the initial growth of seedlings of Lithocarpus edulis, an evergreen oak
○Charissa Maria Maniagasi（宮大農），Satoshi Ito, Ryoko Hirata，Hina Haratani	The nutrient storage of underground cotyledon in acorns of oak species must have significance on successful establishment under shaded conditions. This study aims to evaluate how much growth of matebashii (Lithocarpus edulis) during the first year after germination depends on the nutrient reserve in the cotyledon. We Measured growth and dry mass of seedling germinated from acorns under 100% dark environment and compared them with those under open environment. Final weight of plant organs showed linear relationships with the initial cotyledon weight under both and dark and open conditions, indicating strong dependence of the initial growth on the cotyledon nutrient reserve. However, the relative contribution rate of the cotyledon, which was calculate as the fraction of the total plant weight under dark condition to that under the open condition, did not vary largely along the initial cotyledon weight, and ranged from ca.32-37%. These results indicated that the more cotyledon reserve can produce the more photosynthetic organ, which resulted in the similar relative contribution rate of cotyledon irrespective of the amount of the cotyledon reserve.

401

Relative contribution of cotyledon nutrient reserves to the initial growth of seedlings of Lithocarpus edulis, an evergreen oak

○Charissa Maria Maniagasi（宮大農），Satoshi Ito, Ryoko Hirata，Hina Haratani

The nutrient storage of underground cotyledon in acorns of oak species must have significance on successful establishment under shaded conditions. This study aims to evaluate how much growth of matebashii (Lithocarpus edulis) during the first year after germination depends on the nutrient reserve in the cotyledon. We Measured growth and dry mass of seedling germinated from acorns under 100% dark environment and compared them with those under open environment. Final weight of plant organs showed linear relationships with the initial cotyledon weight under both and dark and open conditions, indicating strong dependence of the initial growth on the cotyledon nutrient reserve. However, the relative contribution rate of the cotyledon, which was calculate as the fraction of the total plant weight under dark condition to that under the open condition, did not vary largely along the initial cotyledon weight, and ranged from ca.32-37%. These results indicated that the more cotyledon reserve can produce the more photosynthetic organ, which resulted in the similar relative contribution rate of cotyledon irrespective of the amount of the cotyledon reserve.

402	An attempt to identify physiological characteristics in current-year shoots of sawtooth oak seedlings before, during and after dormancy
○比江島尚真（鹿大農），鵜川信，渡部由香	Acknowledging the physiological characteristics that are present before, during and after dormancy in trees will provide fundamental knowledge that contributes to evaluating the impact that global warming will have on dormancy. Here, we used sawtooth oak, a deciduous species widely inhabiting the temperate region, as a reference to elucidate physiological characteristics that are present before, during and after dormancy. To achieve this objective, twigs, foliage and buds of one-year-old sawtooth oak seedlings were subjected to monthly measurements of water content, relative water content, respiration rate, starch concentration, sugar concentration and abscisic acid concentration from September, 2021 to March, 2022. The temporal fluctuation of starch was more evident compared to the other measurements. Before dormancy, starch depleted in foliage as yellowing progressed. During dormancy, starch depleted in both twigs and buds. After dormancy, starch accumulated in twigs. From these results, it may be suggested that the breakdown of starch after the growing season plays a role in maintaining carbon-based metabolic activities. Moreover, the accumulated starch in twigs after dormancy might assist in the resumption of vegetative growth.

402

An attempt to identify physiological characteristics in current-year shoots of sawtooth oak seedlings before, during and after dormancy

○比江島尚真（鹿大農），鵜川信，渡部由香

Acknowledging the physiological characteristics that are present before, during and after dormancy in trees will provide fundamental knowledge that contributes to evaluating the impact that global warming will have on dormancy. Here, we used sawtooth oak, a deciduous species widely inhabiting the temperate region, as a reference to elucidate physiological characteristics that are present before, during and after dormancy. To achieve this objective, twigs, foliage and buds of one-year-old sawtooth oak seedlings were subjected to monthly measurements of water content, relative water content, respiration rate, starch concentration, sugar concentration and abscisic acid concentration from September, 2021 to March, 2022. The temporal fluctuation of starch was more evident compared to the other measurements. Before dormancy, starch depleted in foliage as yellowing progressed. During dormancy, starch depleted in both twigs and buds. After dormancy, starch accumulated in twigs. From these results, it may be suggested that the breakdown of starch after the growing season plays a role in maintaining carbon-based metabolic activities. Moreover, the accumulated starch in twigs after dormancy might assist in the resumption of vegetative growth.