Dry Matter Production by Chamaecyparis pisifera in Winter

Photosynthetic activity and dry matter production during winter were investi- gated in the excised twigs of Sawara cypress Chamaeeyparis pisifera, compared with those in the other seasons. 1. In winter, the chlorophyll content of colored leaves of this conifer, which were brown in appearance, had been reduced by half of that of the leaves remaining in green. 2. Net photosynthetic rate of green twigs in winter was positive, though it was at a low level of one third of summer rate. The colored twigs showed more remarkably depressed net photosynthetic rate, and their light compensation point ascended markedly. 3. A positive productivity of green twigs in winter can be observed only in the case of moderately low temperature; under an optimal condition in winter, it was estimated at 3.1 mg. dry matter/g. fresh weight/day, i. e. about one sixth of summer maximum productivity. The colored leaves could have a productivity of only one fifteenth of the summer value.