Shoot tip temperature is one of the important factors to affect morphological development of plants. Energy budget equation can be applied to estimate the shoot tip temperature and cuticle resistance of plant shoot tip is essential to calculate the energy budget.
A method for measuring cuticle resistance of a plant shoot tip was newly developed. The theoretical equation to calculate the cuticle resistance was derived from the energy budget equation, which is consisted of radiation, convection and transpiration. The derived equation is the function of drybulb temperature, wetbulb temperature, glazing material temperature, air velocity, and the relation between vapor pressure deficit and difference between drybulb and shoot tip temperature. The drybulb, wetbulb, glazing material temperatures and air velocity can be directly measured, and the relation between vapor pressure deficit and difference between drybulb and shoot tip temperature is experimentally determined.
The experiment was conducted to obtain the directly measured values and determine the relation mentioned above using Poinsettia crops in a greenhouse.
The procedure of the experiment was that the vapor pressure deficit of the greenhouse was changed with maintaining the drybulb temperature. These values and relation were put into the developed equation and then the cuticle resistance of Poinsettia shoot tip was calculated approximately 960 s/m.

View full abstract

The energy balance of a closed-type transplant production system with artificial lighting was investigated. Sweetpotato (Ipomoea batatas (L.) Lam. cv. Beniazuma) plants were grown for 15 days at photosynthetic photon flux on the tray surface of 100, 200 and 300 μmol m^-2 s^-1 on days 0-2, 3-11 and 12-14, respectively, air temperature of 30°C, CO₂ concentration of 1000 μmol mol^-1, relative humidity of 80/100% (photoperiod/dark period) inside the system and photoper-iod of 16 h d^-1. The amount of electric energy consumption during the 15 days for lighting, cooling and the other equipment per planting area were 375.5, 80.8 and 41. 1 MJ m^-2, respectively. Electric energy consumption per plant was 1.8 MJ (0.5 kWh), and its cost was approximately 4-5 Japanese Yen. Coefficient of performance for the cooling system was approximately 4.7, which was 2 times higher than the value described in the catalog, partly because the air temperature inside the system was higher than that of outside the system. The ratio of electric energy consumption to chemical energy assimilated by plants (energy use efficiency of the system) was 0.006. These results show that the closed-type transplant production system is feasible for the commercialization. Methods for further reduction of electric energy consumption (increasing the energy use efficiency of the system) and electricity cost are discussed.

View full abstract

Growth and mineral absorption of Japanese bunching onion (Allium fistulosum L. cv. Yakko) were observed using various fertilizing solutions whose ratio of NO₃-N and NH₄-N was varied. Plant growth was remarkably suppressed when the plants were fertilized by a solution in which the ratio of NO₃-N and NH₄-N was 0 : 10. The root growth, especially of the secondary roots, was relatively more affected than the top growth, which was presumably due to a big stress of ammonium nitrogen. The fact that plant growth was considerably improved when the ratio of NO₃-N and NH₄-N in a fertilizing solution was changed once on the way from 10 : 0 to 0 : 10 or from 0 : 10 to 10 0, suggested the effectiveness of a temporary supply of NO₃-N to the plants. With an increase of NH₄-N in the ratio of both nitrogen forms in a fertilizing solution, the contents of Ca, Mg, K and NO, -N in the leaf blade decreased. Occurrence of leaf tip withering was positively correlated with root browning and with NH₄-N content in the leaf blade, while it was negatively correlated with the contents of Ca and Mg in it.

View full abstract

A computer software program for aiding the mixture of macronutrients in nutrient solutions, named 'IonAdjuster', has been developed to select the best combination from various nutrient sources to determine required addition rates, according to user-specified demand and current analysis results. This software program is a personal computer spreadsheet program that runs on Excel 97. The user specifies the desired solution composition suitable for a cultivated plant by means of milli-equivalents or weight per volume of macronutrients. IonAdjuster determines the quantity of concentrated stock solution to be added from differences in required composition and the present macronutrient concentrations in solution. In practical hydroponic culture of tomatoes, fluctuation of ion contents of the solution was decreased and the percentage of top-grade fruit increased by the nutrient stock addition according to IonAdjuster. It is assumed that the combination of IonAdjuster and automatic ion sensing, such as that by a multi-ion meter, may allow for appropriate and continuous control of solutions in closed hydroponics. This developed system may result in higher crop production, more efficient use of fertilizer and elimination of groundwater pollution due to the drainage of large amounts of nutrient solutions from open hydroponic systems.

View full abstract

In this study, a new cultivation system using porous ceramic pipes with negative pressure was successfully developed, by which the water content of soil could be auto-controlled to suitable values for vegetable growth. In this cultivation system, the nutrient and water can be autosupplied to roots continuously and timely, when necessary. The response of the soil pF to the inner negative pressure of the ceramic pipe and its irrigation rate were also studied. During cultivation experiment of lettuce, the soil pF of the new system could always be maintained at suitable values (1.3-1.5) for the growth of lettuce, while the pF in the usual soil cultivation fluctuated widely (0-1.9). The growth and yields of lettuce cultivated in the new system were significantly better than that in the usual soil culture. The developed cultivation system would be a useful and practical technique for vegetable production.

View full abstract

In a previous report, we have revealed that the bio-electric potential signal of Grifora Frondosa was significantly affected by blue light stimuli under constant temperature and humidity.
In this study, we have investigated intensity dependence and effects of fluctuations of blue and red light stimuli on the morphogenetic properties of Grifora Frondosa in a growth chamber.
We obtained the following results :
(1) The blue light stimuli significantly accelerated mushroom growth.
(2) Growth was further accelerated when 1/f fluctuating blue light was used.

View full abstract

Removal of the cotyledons of eggplant seedlings by ethrel (chemical name : 2-chloroethylphosphonic acid) and brushing treatment was examined to obtain the height to the cotyledons suitable for grafting robot. Effects of spraying of 800 ppm ehtrel and brushing on the removal of the cotyledons for 'Senryou-2gou' seedlings, and 400 ppm ethrel and brushing for 'Akanasu' and 'Daitarou' seedlings were obtained. The vegetative growth and flowering of eggplant seedlings before and after grafting were unaffected by ethrel treatment.

View full abstract