Photosynthetic properties of leaves are compared among saplings of tree species. The interspecific difference is insignificant in maximal rate of net photosynthesis (P_max) but is recognized in initial slope of light response curve (x) . Values of α are largest in C. controversa and smaller in M. kobus and Q. mongolica var. grosseserrata: P. verecunda and Q. serrata have intermediate values. Under exposure to an irradiance of 1, 400μmol quanta m^-2 sec^-1, the photosynthetic response (P^*) declines rapidly for Q. serrata and Q. mongolica, whereas the other tree species show no rapid decreases at least for 5 min, also followed by relatively gentle decreases. The photosynthetic reduction of P_max by the 60-min exposure to high light ranges from 16% of M. kobus to 35% of P. verecunda and that of a from 28% of Q. mongolica to 55% of P. verecunda, significantly differing due to species. However, the extent of photosynthetic reduction of P_max or α is not directly correlated with the decrease in P^*. It is saplings of C. controversa that is presumably able to utilize most efficiently both weak and strong light under the actual light regime of the forest floor. Saplings of Q. serrata and Q. mongolica, by contrast, have no particularly advantageous photosynthetic properties to either use of weak light or that of strong light.

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The purpose of this investigation was to estimate the root resistances to water movement. The total root resistances and the root conductive resistances were measured using the pressure chamber method and the siphon method, respectively. The absorptive resistances were calculated from the measured resistances assuming a simple model of a root system. The results are summarized as follows. 1) The total root resistance changes with the flow rate from the root base. The result suggests that the resistance changes with the transpiration rate. The resistance decreases as the water absorptive rate from the root increases and converges to a constant value. 2) When the total root resistance becomes a constant, the absorptive resistance of sunflower occupies 82% of the total resistance, while the conductive resistance of third root 1% and that of secondary root 18%. The absorptive resistance of corn, however, accounts for 99% of the total resistance. 3) The water flow through root vessels can be considered as a Hagen-Poiseulle's flow. The value of the conductive resistance through root vessels of corn is almost equal to the theoretical value obtained by Hagen-Poiseulle's equation. However, as for sunflower, wheat and soybean, the value is 3.5 to 5 times as large as the theoretical value.

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In order to promote the growth of redifferentiated carrot (Daucus carota L.) plantlets in vitro in MS medium, changes in the concentration of the medium components and in the quantity of nutrient uptake were investigated. Eight somatic embryos of carrot were placed on medium-supports (made of formed polyester wool) containing 60 ml of MS medium with 1.5% sucrose in a culture vessel (60×60×100 mm) and cultured. From 1 week after placing, growth of the plantlets and concentrations of inorganic and sugar components were measured every week. Phosphate concentration of MS medium and growth rate of the plantlets decreased in the late stage of carrot tissue culture and phosphate uptake by the plantlets also decreased with increase of the dry weight. Phosphate added into the MS medium in the late stage of cultivation increased height and dry weight of the plantlets. It was found that the standard phosphate concentration in MS medium became insufficient in the late stage of cultivation of carrot plantlets, and adding supplement of phosphate into the medium promoted growth.

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In order to diagnose physiological activities of individual trees growing in urban area, a remote sensing using a thermographic system from a helicopter was examined at the temple of“Heirin-ji”and adjascent area in Saitama Prefecture. Under cloudy and steady-state thermal conditions the information about activities of physiological functions such as stomatal movement, transpiration, photosynthesis, and air pollutant absorption was obtained from the thermal image of trees. The slight injury, which was found in the field survey of individual trees, was diagnosed by the thermal image, although it was not detected from aerial photographs in color. The difference in species of trees was also detected by the thermal image.
The stomatal conductance of several tree species measured by a porometer, which is an indicator of stomatal opening, decreased with a lowering of PPFD. The decrease rate was large at PPFD below 200μmol photons m^-2 sec^-1 but it was small and constant at PPFD above 300μmol photons m^-2 sec^-1. This result means that it is possible to diagnose stably the slight injury of trees from the thermal image measured under a cloudy sky with PPFD above 300μmol photons m^-2 sec^-1.
The resolution and error in temperature image measured by the thermographic system depended on spatial distributions of temperature. When the difference (5°C) between high and low temperatures in the image was given by slits with zigzag patterns, the resolution and error were ca. 300 lines and ca. 5% (0.25°C) at 50 slits. This result shows that it is necessary to measure at a height below 300 to 500 m in order to obtain the exact temperature of individual trees within 5% in error.

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The leafy single node cuttings of potato (Solanum tuberosum L. cv. Benimaru) plantlets cultured in vitro were cultured under photomixotrophic conditions, and the effect of the lighting cycle on the growth and morphology of the plantlets into which the cuttings in vitro was examined under the following four lighting cycle treatments: (1) 16 hr photoperiod/8 hr dark period; (2) 4 hr photoperiod/2 hr dark period; (3) 1 hr photoperiod/ 0.5 hr dark period; and (4) 0.25 hr photoperiod/0.125 hr dark period. The ratio of the photoperiod to the dark period was 2: 1 in all treatments. Therefore, the amount of electricity for lighting per day was the same in all the treatments. The CO₂ concentrations inside and outside the vessels were measured at time intervals of 0.0625-2.5 hr.
On day 28, the dry fresh weights per plantlet were greater in the shorter lighting cycle treatments than in the longer lighting cycle treatments. However, the length of the newly developed shoots of the plantlets was the shortest, and the leaf dry weight and leaf area per plantlet were the greatest in the 1 hr photoperiod/0.5 hr dark period treatment.
The difference in CO₂ concentration between the inside and outside of the vessel, ΔC, during the photoperiod increased with the passage of days after treatments and was greater in the longer lighting cycle treatments than in the shorter lighting cycle treatments. The ΔC during the photoperiod showed a low constant value for a longer time in the longer lighting cycle treatments than in the shorter lighting cycle treatments. The differences in growth of the potato plantlets among the treatments seemed to be primarily influenced by the differences in CO₂ concentrations in the vessels among the treatments.

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