Seasonal changes in leaf chlorophyll contents of eight tree species, Quercus glauca, Cinnamomum camphora, Rhaphiolepis umbellata, Quercus myrsinaefolia, Pittosporum tobira, Ulmus parvifolia, Zelkova serrata and Quercus serrata, were measured with Chlorophyll Meter SPAD-502 for 13 months. The differences in the regression lines between SPAD value and chlorophyll contents of each species indicated that SPAD value was affected by leaf thickness and chlorophyll contents of each species. SPAD value for old leaves of Quercus glauca and Cinnamomum camphora showed a gradual decrease from winter to spring. Although most old leaves were defoliated just after the flush of new leaves, SPAD value in 2-year-old leaves remaining on branch increased in spring. On the other hand, leaves of Rhaphiolepis umbellata and Pittosporum tobira were discolored just before the defoliation in spring. Deciduous tree species showed a rapid increase in SPAD value for new leaves in comparison with evergreen tree species. Three types of relationships between leaf area and SPAD value of new leaves were detected during the period of leaf elongation in spring. It indicated species differences in the balance of chlorophyll production and leaf development in the beginning of flush.

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Photosynthesis and transpiration of tulip tree (Liriodendron tulipifera) were measured in Kagawa University, Marugame Station Square and Kinbuchi Forest Park, and at the same time, soil conditions and root distributions were investigated.
The growth of the leaf area finished for about 20 days, but it took about one month to mature chlorophyll.
In case of the trees in Kagawa University and Kinbuchi Forest Park, light-saturated photosynthetic rate increased with the chlorophyll content of the leaf. The light-saturated photosynthetic rate of the mature leaves showed more than 10μmolCO₂/m²/s, but it greatly dropped at the drought period in summer. Water Use Efficiency, that is the ratio of photosynthetic rate to transpiration rate, decreased from spring to summer, and increased from summer to fall. It is supposed that drought in summer greatly influenced the photosynthetic activity. The root systems of both trees were very shallow because of dense soil conditions. So, it seemed that the trees were apt to be influenced by drought.
In case of the tree in Marugame Station Square, the photosynthetic rate was low and unstable. It seemed that the reason was lack of soil water. Because, the tree was planted on the artificial ground above the underground parking and the ground surface around the tree was paved with asphalt and stones. So, the supply of underground water and infiltration of rain into the soil were not expected. In addition, irrigation was not sufficient.

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Effects of spray of pH 2, 3 and 4 sulfuric acid solutions (5, 0.5 and 0.05 mM/1 respectively) on growth, biomass increment, levels of indoleacetic acid (IAA) and abscisic acid (ABA), and ethylene production in seedlings of woody plants were investigated. The application of the pH 2 solution to the shoot system of plants with a hand spray for 2 months significantly decreased growth and biomass of Cryptomeria japonica, Chamaecyparis obtusa, Pinus densiflora, Betula platyphylla and Ulmus americana seedlings. The pH 2 solution also enhanced ethylene production in these species. In B. platyphylla and U. americana seedlings, defoliation was accelerated by application of all of the acid solutions. The IAA content in needles or leaves was noticeably reduced in C. japonica, C. obtusa, P. densiflora and B. platyphylla seedlings by acid application, however, the ABA content was not affected.

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To explain the process of CO₂ and H₂O diffusion between air and plant, analysis was made using a data set concerned with diurnal and seasonal variation of transpiration and net CO₂, assimilation rate on leaves of three evergreen broad-leaved trees (Quercus glauca, Cinnarnornum carnphora and Pasania edulis).The observation results about the pattern of diurnal and seasonal change are as follows:(1) Diurnal variation: the pattern of transpiration rate had the peak about at noon, whereas the pattern of net CO₂ assimilation rate had the peak in the morning.(2) Seasonal variation: bigger seasonal variation in transpiration rate compared with net CO₂ assimilation rate were observed.(3) Water-use efficiency: the values are higher in the morning or in winter than in the afternoon or in summer.Two parameters, stomatal conductance and internal conductance, were used to explain the observation results.From this analysis it is shown quantitatively that stomatal conductance is not the single physiological component deciding CO₂ flux and the influence of internal conductance is not negligible. Moreover, it could be explained by analyzing water-use efficiency which environmental and plant factor mainly caused the differences of the pattern of the diurnal and seasonal variation between transpiration rate and net CO₂ assimilation rate.

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