|Budget Amount *help
¥5,800,000 (Direct Cost : ¥5,800,000)
Fiscal Year 1992 : ¥1,400,000 (Direct Cost : ¥1,400,000)
Fiscal Year 1991 : ¥1,400,000 (Direct Cost : ¥1,400,000)
Fiscal Year 1990 : ¥3,000,000 (Direct Cost : ¥3,000,000)
Seasonal changes in several forms of nitrogen (total-N, total soluble-N, free amino acids) in various component organs, chlorophyll content and light-saturated photosynthetic rates of foliage leaves were investigated in two evergreen temperate woodland hemicryptophytes (Pachysandra terminalis and Coptis japonica), two deciduous hemicryptophytes (Allium vistorialis ssp. platyphyllum and Erythronium japonicum), and one bulbous perennial ruderal (Allium grayi). In two evergreen perennials, the concentration of total nitrogen in rhizomes and roots decreased from winter to spring, indicating the plant's utilization of new shoot growth in spring. In the rhizomes, total soluble protein stored by early summer decreased gradually until winter, coupled with an increase in free amino acids. Nitrogen was largely pooled in free amino acids in the roots, especially in summer. The content of total soluble protein in the current-year leaves decreased from spring to summer and then increased in winter.
This seasonal change was coinncident with the change in light-saturated photosynthetic rates obtained in a previous study. In contrast, chlorophyll content and the ratio of chlorophyll to total nitrogen was higher in summer than in other seasons. The results indicate that nitrogen was used in a manner which better utilizes a very weak light in summer and the relatively high light intensities in other seasons. The major component of the free amino acid pool was asparagine in every organ throughout the season. Seasonal changes in nitrogenous fractions in various organs of two deciduous woodland perennials, Allium victorialis ssp. platyphyllum and Erythronium japonicum, were also coincident with the changes in light-saturated photosynthetic rates. High concentrations of total soluble protein and free amino acids were found in winter and also in late summer. It is also noteworthy that glutamine was one of the major free amino acid fractions in the bulbs of these two woodland hemicryptophytes in winter. On the other hand, arginine and asparagine were richest in early to late summer in E. japonicum and A. victorialis var. platyphyllum, respectively. Seasonal changes in dry matter allocation, and carbon-nitrogen economy of Allium grayi were also critically analyzed. Most unique turnover patterns of N-fractions and C/N ratios were discovered from this ruderal perennial, which obviously reflects a very unstable, changing conditions of the habitats of this species.