Experiments were made in an attempt to determine the effect of ozone fumigation on the rate of CO₂ exchange both in the light (24 klux) and in the dark of detached poplar leaves. The rate of CO₂ exchange was determined before and after the exposure to 0.9 ppm ozone at 25°C with the air flow rate of 1.5 liter min^-1.
Both net photosynthesis and CO₂ evolution in the light were considerably decreased. However, dark respiration was increased after the ozone fumigation. The light and CO₂ compensation points were significantly higher in the ozonated leaves. The results of these experiments are discussed.

View full abstract

An attempt of indoor experiment has been made to determine the apparent photosynthesis of several benthic marine algae as an indicator of the effect of marine pollution at Tagonoura Port located in the innermost part of Suruga Bay.
The materials used in this study were 2 species of Chlorophyceae, 3 species of Phaeophyceae and 6 species of Rhodophyceae.All the plants were collected along the coast of six different localities in Suruga Bay. The experiments were carried out with Differential Gas-Volumeter (Yokohama and Ichimura, 1969) under the conditions of 20°C sea water temperature and 20 klux light intensity.
The results obtained are summarized as follows:
1) In most species examined photosynthetic activity was apparently inhibited with increase of concentrations of pollutants.
2) In only one species, Enteronorpha intestinalis, collected on the coast of two different localities, a strong resistance to high concentration of pollutants was observed, and the rate of photosynthesis at concentration of 25% was approximately 3 times of that at concentration of 0%.
3) It can be said that the green algal species of Enteromorpha may be useful for assaying the pollution of sea water.
4) Photosynthesis-inhibition in algae such as Sargassum hemiphyllum, Eisenia bicyclis, Gelidiuna amansii and Hypnea japonica from the sublittoral zone was more remarkable than in those such as Ulva pertusa, Scytosiphon lomentarius and Porphyra from the intertidal zone.

View full abstract

The experiments were carried out to ascertain the effect of day and night temperature on the growth and flower formation of egg-plant.
1. Effect of thermoperiod on the vegetative and reproductive responses
Seedlings were grown at the following seven different thermoperiods:
Experiment Day temperature-Night temperature
I {15°C-10°C20°C-15°C25°C-20°C30°C-25°C
II {17°C-12°C23°C-18°C30°C-25°C
Combination of high temperature treatments induced the vigorous growth followed with the earlier flower bud differentiation, development and the increased number of flowers.
2. Effect of night temperature on the vegetative and reproductive responses
Seedlings were grown at combinations of day temperature 30°C and various different night temperatures. The higher the night temperature up to 25°C, the more vigorous the seedling growth, the earlier the date of flower bud differentiation, and the more the number of flowers. The night temperature higher than 25°C, on the other hand, restricted the seedling growth and retarded the flower bud differentiation, resulting in the increase in the number of leaves to the first flower.
3. Effect of low night temperature at various stages of seedling growth on flowering behaviour
Seedlings were grown at day temperature 30°C and night temperature 25°C, and subjected one, two and three weeks to the low night temperature 12°C and/or 18°C at various stages of seedling growth, and then they were returned to the original condition. During the course of this experiment the day temperature was maintained at 30°C.
It was found that exposure of seedlings to low night temperature for at least two weeks just after cotyledon expansion resulted in the smallest number of leaves to the first flower.

View full abstract

The influence of osmotic potential and water potential on the leaf expansion and leaf weight were studied with a Japanese native tobacco variety ‘Shiroenshu’grown in irrigated or non-irrigated plots on volcanic ash soil. Water status in leaf, chemical component and yield of irrigated and non-irrigated tobacco were also examined. Leaf area and leaf weight of non-irrigated tobacco were smaller than those of irrigated tobacco. The decrease in leaf area and leaf weight were closely correlated with the depression of pressure potential (turgor pressure) of leaves. The rate of water loss at room temperature of detouched leaves of middle position in the irrigated tobacco was faster than that of the non-irrigated one. The rate of water loss in upper leaves was slower than that in lower ones.
Chlorophyll content in the irrigated tobacco was maintained longer than those in non-irrigated one. It was supposed that the cells of the upper leaves of the irrigated tobacco were kept younger than that of the non-irrigated tobacco. Yield and quality of the irrigated tobacco were higher than those of the non-irrigated one.

View full abstract

A tadpole shrimp, Triops granarius appears in paddy fields a few days after the water submergence and ploughing. The Triops species have many similarities in their ecological characteristics with those of the annual plant weeds in paddy field, such as the life cycle in an annually disturbed habitat, the wide range of food or nutritional requirement, the high persistency of eggs or seeds in drought, the rapid development and maturation, the great overlapping of growing and reproductive stages, the high reproductive power, and the self compatibility in reproduction. As some annual weed species in paddy fields are light-sensitive in their seed germination, T. granarius eggs were also examined in this respect and it was found that the light condition has significant effect on their egg hatching.
The eggs, collected from a paddy field with soils at Ibaraki City, Osaka (Experiments 1 and 2), and oviposited in the laboratory (Experiment 3), were submerged in water and the rate of egg hatching was examined in the darkness and under the various day lengths of illumination by the fluorescent lamp (Toshiba white 20W NL, 40 cm apart) at 20°C. A high percentage of eggs hatched rapidly under the light condition between 8 and 24 hrL. The egg hatching was significantly prevented under the shorter day length of less than 4 hrL as well as in the darkness.

View full abstract

In this paper, characteristics of the digital computer control of temperature in a growth-cabinet were made clear by simulation. Simulation of temperature control system on modelling of a growth-cabinet was carried out by means of hybrid computer. Sampling PID control was carried out by means of digital computer.
Characteristics of K, T_I and T_D were examined with τ-parameter in the simulation.
1) Value of K should be decided upon the relations with manipulating capacity P or τ. Computer control of temperature should be programmed in consideration of proper value of K in steady-state condition or in transient condition.
2) Value of T_I should be smaller in steady-state condition than in transient condition.
3) Value of T_D should be small in either case.
4) Stability of temperature control is better in smaller τ, though it is good in larger τ (τ=20 sec.) on the condition of optimum K, T_I and T_D from the data of simulation.
5) Time constant of detecting means should be examined in consideration of P and K.

View full abstract