Dry bulb (or air) temperature, leaf temperature of tomato plant (Tleaf), and relative humidity were measured under various fogging times (tf) around midday in summer inside a naturally ventilated single-span experimental greenhouse with a fogging system for cooling and with side-wall and roof ventilators which remained open. Then, the evaporative cooling efficiency (η) of the greenhouse, expressed as the ratio of the difference in dry bulb temperature between the outside (Todb) and the inside (Tidb) to the difference between Todb and the outside wet bulb temperature (Towb), was calculated. The fogging system was comprised of a water filter, a water reservoir, a fogging pump, a pressure regulator, and fog-generating nozzles. Fog was applied for periods between 20 and 75 s, separated by intervals of 160 s. For all tf, a drop in Tidb increased with increasing vapor pressure deficit of the inside air (VPDi) at the start of fogging. Tidb reached 6.0°C lower than Todb by fogging. During fogging, Tidb was more or less the same as Tleaf. During the interval, however, Tidb increased and Tleaf tended to remain unchanged. The increase in VPDi resulted in decreased (Tleaf-Tidb) . The η was in the range between -30% and 21% when using the average Tidb, and 57% and 80% when using the minimum Tidb. The η compares favorably with a conventional misting system.
Tomato plants were grown in a bag culture system with a drip irrigation system using coco-nut coir as substrate. For the treatments the same volume of nutrient solution (50mL) with 2 different amounts of NO3-N (0.4 and 0.5 me plant1 MJ-1 m-2) was supplied when cumulative solar radiation value reached 1 MJ m2. Different volumes of water were supplied at the same time as the supply of nutrients. There were 4 additional water supply treatments with varying amounts of water supply for vapor pressure deficit as follows: V-0 (no additional water supply), V-1, V-2, and V-3, respectively with the total of 8 treatments. In the V-0 treatments with both of NO3-N amounts, the contents of total soluble solids in the fruits were the highest, while the leaf dry weight, photosynthetic rate and yield were the lowest. This study revealed that a concentration of 0.4 me NO3-N plant-1 MT-1 m-2 was the optimum for tomato production in this system. The 0.4V-3 treatment was associated with a low percentage of drainage, high water use efficiency and high nitrate use efficiency. The recommendation for fertigation management consisting of varying the amounts of NO3-N and of additional water depending on the data of NO3-N consumption in the 0.4V-3 treatment was explained.
To investigate whether night break (i.e., the interruption of the dark period by artificial lighting) controls plant flowering sufficiently with treatment on alternate days, we compared the reproductive responses of seven horticultural crop species under a daily night-break treatment, an alternate-day treatment, and no night-break treatment during the short-daylength season. Longday crops of spinach (Spinacia oleracea), petunia (Petunia×hybrida), and godetia (Godetia cvs.) and short-day crops of cosmos (Cosmos bipinnatus), perilla (Perilla ocymoides), zinnia (Zinnia elegans), and Japanese morning glory (Pharbitis nil) were used. The night-break treatment was supplied for 2 hours starting at midnight using red light-emitting diodes. The effect of the alternate-day treatment was much smaller than the effect of the daily treatment in zinnia and Japanese morning glory; was smaller in spinach, godetia and cosmos; and was only slightly smaller in petunia. Budding in perilla was inhibited by both night-break treatments.
Inoculation of ectomycorrhizal fungi to nursery-raised tree seedlings can improve survivorship and growth of them when transplanted into the field. This study investigated the effects of ectomycorrhizal inoculation using mycorrhizal tree on Shorea macrophylla seedlings, planted at different intervals, in a tropical nursery. Forest topsoil and river sand were mixed at a volumetric ratio of 1 : 1 as bedding medium. The non-mycorrhizal seedlings and a mycorrhizal tree were planted in a plastic container (length=75 cm, width=25 cm, depth=14 cm), with the seedlings spaced at 20-cm and 30-cm intervals from the tree. These seedlings were raised for 6 months at a nursery of the Lambir Hills National Park, Miri, Sarawak, Malaysia. Mycorrhizal formation percentage, dry matter weight, and nutrient content of the seedlings and soil properties of the bedding media were measured. The ectomycorrhizal infection could transfer from mycorrhizal tree to the seedlings by the elongation and connection of rhizomorph in both 20-cm- and 30-cm-interval treatments. The ectomycorrhizal inoculation would be better when the seedlings were planted closer to mycorrhizal tree, i.e., at 20-cm interval. Early phase infection and greater mycorrhizal formation might improve nutrient acquisition such as N under poor nutrient condition.
To produce the high quality tomato fruits, plants are grown in soilless culture with the special features by controlling the nutrient solution. This effort highly requires real-time bioinformation of fruit internal properties during growth for feedback in routine control of the nutrient solution. The dry matter (DM) and starch content of the growing fruits are mainly correlated to ripe-stage soluble solids content (SSC) as an important quality parameter. In this study, the “on-site” near infrared (NIR) measuring system was successfully developed as a nondestructive method for determination of DM and starch content in growing fruits. As the temperature of fruit in field could not be controlled, the problem could be solved using a calibration model with temperature compensation. Here, the high performance of this measuring system for monitoring on-plant fruit was also demonstrated. The equations developed from the monitoring results of DM and starch content could be used to predict the SSC of ripen fruits. The use of “on-site” NIR measuring system developed, makes it possible to control and modify the nutrient solution (e.g. EC level) based on the internal properties of immature fruits to produce tomatoes at the desired SSC level.
The physiological adaptation response to environmental stress of a plant can induce changes in physiological and physical conditions of the plant. These changes influence the dielectric properties of the plant, which can be detected by measuring complex dielectric properties of plant materials. The dielectric properties of tomato leaves during salt stress at NaCl concentrations of 0, 50, 100 and 200 mmo1L-1in nutrient solution were measured with an open-ended coaxial probe from 0.3 to 3 GHz, as well as changes in water content, photosynthetic rate, stomatal conductance and water potential which reflect the physiological condition of the plant. Experimental results showed the potential of microwave sensing as a method for monitoring adaptation responses in tomato plants under salt stress. In order to clarify the principle of detecting adaptation responses to salt stress by microwave method, chemical analyses were conducted. The chemical analyses results suggest an increase in the effects of osmoregulation by the tomato plant. The dynamic adaptation responses of the tomato plant to salt stress can be detected non-invasively by microwave sensing which detects the changes in complex dielectric properties of the plant.
The effects of calcium (Ca) application on fruit firmness, ethylene concentration and Ca uptake of ‘Jonagold’ apple [Malus sylvestris (L.) Mill. var.domestica (Borkh.) Mansf.] were investigated. A 2.5 g⋅L-1Ca (1.425g⋅L-1calcium sulphate dihydrate, 0.675g⋅L-1calcium chloride and 0.4 g⋅L-1others) solution was applied to whole tree at 4 days intervals from 20 to 60 days after full bloom (DAFB) . Ca treatment decreased internal ethylene concentration compared to the untreated control. Bound Ca concentration in the cell wall of Ca-treated fruit was higher than that of untreated control. Although the firmness of Ca-treated fruit showed higher value than that of the control before coloring, they had no significant difference after coloring. These results demonstrate that Ca treatment at 20-60 DAFB may prevent the increase of ethylene production, resulting in the delay of fruit senescence, prior to coloring, which is often observed in warm regions.
The effect on fruit set and stigma receptivity of a pre-pollination treatment with 0.75 μ11-11-MCP, an inhibitor of ethylene action, was tested in flowers of ‘Housui’ Japanese pear (Pyrus pyrifoliaNakai) . 1-MCP increased the fruit set and the number of stigmas with pollen germination in flowers hand-pollinated at 6 and 7 days after anthesis. Twenty hours afterin vitropollination, 1-MCP reduced the ethylene production of pollinated and non-pollinated styles of 1 day after anthesis flowers. Collectively, these results suggest that style senescence was delayed by 1-MCP resulting in the higher fruit set in late pollinated flowers.