title: Growth and photosynthetic traits of hybrid larch F1 (Larix gmelinii var. japonica x L. kaempferi) under elevated CO2 concentration with low nutrient availability.
abstract: The hybrid larch F(1) (Larix gmelinii var. japonica × Larix kaempferi) is considered one of the most important tree species not only for timber production but also as an afforestation material for severe conditions such as infertile soil. To predict the ability of hybrid larch F(1) as an afforestation material under potential climates in the future, it is important to understand the response of hybrid larch F(1) to elevated CO(2) concentration ([CO(2)]) under low nutrient availability. Three-year-old seedlings of hybrid larch F(1) were grown under two different levels of [CO(2)], 360 (ambient) and 720 µmol mol(-1) (elevated), in combination with two different levels of nitrogen (N) supply (0 and 30 kg ha(-1)) for one growing season. Elevated [CO(2)] reduced the maximum rates of carboxylation and electron transport in the needles. Net photosynthetic rates at growth [CO(2)] (i.e., 360 and 720 µmol mol(-1) for ambient and elevated treatment, respectively) did not differ between the two CO(2) treatments. Reductions in N content and N use efficiency to perform photosynthetic functions owing to the deficiency of nutrients other than N, such as P and K, and/or increase in cell wall mass were considered factors of photosynthetic down-regulation under elevated [CO(2)], whereas stomatal closure little affected the photosynthetic down-regulation. Although we observed strong down-regulation of photosynthesis, the dry matter increase of hybrid larch F(1) seedlings was enhanced under elevated [CO(2)]. This is mainly attributable to the increase in the amount of needles on increasing the number of sylleptic branches. These results suggest that elevated CO(2) may increase the growth of hybrid larch F(1) even under low nutrient availability, and that this increase may be regulated by changes in both crown architecture and needle photosynthesis, which is mainly affected not by stomatal limitation but by biochemical limitation.
authors.affiliation: Research Fellowship of Japan Society for the Promotion of Science, Chiyoda-ku, 102-8472, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Watanabe
authors.forename: Yoko
authors.initials: Y
authors.lastname: Watanabe
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kitaoka
authors.forename: Hajime
authors.initials: H
authors.lastname: Utsugi
authors.forename: Kazuhito
authors.initials: K
authors.lastname: Kita
authors.forename: Takayoshi
authors.initials: T
authors.lastname: Koike
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism*; D002678:Chimera; D015536:Down-Regulation; D004579:Electron Transport; D017752:Greenhouse Effect; D007564:Japan; D028221:Larix / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D009584:Nitrogen / Q000378:metabolism; D010758:Phosphorus / Q000378:metabolism; D010788:Photosynthesis; D018515:Plant Leaves / Q000378:metabolism; D054046:Plant Stomata / Q000378:metabolism; D011188:Potassium / Q000378:metabolism; D036226:Seedlings / Q000254:growth & development / Q000378:metabolism; D014197:Trees / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*
chemical_list: D002245:Carbon Dioxide; D010758:Phosphorus; D009584:Nitrogen; D011188:Potassium