An effective control logic for a high-pressure fog cooling system for a naturally ventilated greenhouse has been developed. A suitable duration of the fog cooling system operating time is estimated using weather data and the target relative humidity inside the greenhouse with a computational model based on mass and thermal balances of the greenhouse air. The program has three main tasks: (1) to read the dry bulb temperature set point inside the greenhouse for fogging system operation and the target relative humidity defined by the user; (2) to compute a suitable duration of the fog cooling system operation; and (3) to display relevant output information to the user. The duration of fog cooling system operation decreased as the water vapor pressure deficit inside the greenhouse decreased. The control logic of the fog cooling system would be used to lower dry bulb temperature by increasing the relative humidity to the target value. Our results prove that implementing this control logic for greenhouse fog cooling system is technically feasible.
To understand the vital role of roots in plant growth, it is essential to know the dynamics and distribution of the plant root system. Research in this area has been limited severely by labor intensive techniques used for determination of physical characteristics of roots, especially fine roots. Nowadays, with development of various image analysis applications, it is possible to use methods that speed the process of fine root quantifying and, therefore, allow many more samples to be collected and processed for study. The accuracy of root measurements and time required greatly depend on the capabilities of the image acquisition equipment and the employed root preparation technique. At the same time, the optimal use of image analysis software can improve dramatically both precision and measuring speed. Our objective was to examine some fine root measuring issues common to most image analysis applications. These problems include choosing the proper image resolution, determining the appropriate threshold range and image parameters to measure, as well as reducing the impact of non-root objects on measurement accuracy. Using a numerical example, we describe techniques that can be used to minimize these problems and optimize the precision and accuracy of measurements. Our results suggest that optimal scanning resolution can be determined based on prior determination of root diameter and the minimum root diameter in an image must contain no less than three pixels. We also found that variation in measured root length can by minimized by determining threshold ranges. By applying numerical filters to images, we were able to decrease background noise ; however determination of the optimal filter ranges needed to be performed individually for each application and depend on the size of scanned roots and image resolution. The combined effect of using optimal image resolution, threshold ranges, and numeric filters can increase the efficiency of fine root image analysis in terms of precision and speed.
There is increasing interest in growing medicinal plants under controlled environments for phytopharmaceutical products, partly because it provides safety and efficacy. However, few studies on medicinal plant production under controlled environments have been reported. In the current study, St. John's wort, a traditional medicinal plant with antidepressive properties, was grown in a controlled environment system (CES) and in the field in summer (FS) and winter (FW) . Despite the higher planting density in the CES-treatment, plants showed the greater biomass and secondary metabolite production than those of the plants in both the FS-treatment or FW-treatment. Total dry mass per plant in the CES-treatment was 2.4 and 2.1 times greater than those of plants in the FS-and FW-treatments, respectively. Leaf net photosynthetic rate and chlorophyll a concentration were higher in the CES-treatment than in the FS-treatment or FW-treatment. The hypericin, pseudohypericin and hyperforin contents (mg plant-1) in leaf tissues in the CES-treatment were 6.1, 5.6 and 10.6 times greater, respectively, than those in the FW-treatment. Therefore growing medicinal plants under a controlled environment appears to provide high biomass and secondary metabolite production.
Hot air and hot water are being extensively studied as postharvest heat treatments for retaining freshness and extending shelf life of many fruits and vegetables during storage. In the present study, the best combination of several types of heat stress application methods that minimizes water loss of fruit during storage were investigated, aiming at the practical use. The heat stress application allowed the water loss of the fruit during storage to be successfully reduced. The combinatorial double heat shock treatment where the hot air was first applied for 6 h at 40°C followed by hot water dipping for 6-12h at 40°C showed the best performance at the final stage in all other treatments including single hot air, hot water, hot water + hot air and control (non-heated) in minimizing the water loss of oranges during storage. This heat stress technique (HA + HW) is useful for successful storage of orange.
Drought stress was applied to ‘Shiranui’ trees [ (Citrus unshiu Marc. × Citrus unshiu Osbeck) × Citrus reticulata Blanco], and xanthoxin, abscisic acid (ABA), phaseic acid (PA), dihydrophaseic acid (DPA), epi-dihydrophaseic acid (epi-DPA), and jasmonates were monitored in fruit and leaf. They were quantified using the respective deuterium-labeled internal standards. Xanthoxin, ABA, and DPA concentrations in the pulp of the drought-stressed trees were found to be higher than those of the well-watered trees throughout development. Xanthoxin concentrations, however, were lower than those of ABA. These results may imply a rapid turnover from xanthoxin to ABA. In addition, ABA concentrations in the leaf were higher in drought-stressed trees than the well-watered trees, although PA and DPA levels between the drought-stressed and well-watered trees were not clear. DPA was found to be the primary metabolite in the pulp, skin, and leaf. Both jasmonic acid (JA) and ABA concentrations in the pulp, skin, and leaf showed high values in the drought-stressed trees. However, JA levels in the pulp decreased as the harvest approached. Sucrose concentrations in the pulp of the drought-stressed trees were higher than those of the well-watered trees. ABA and jasmonate applications induced stomatal closure in leaf The effect of ABA on stomatal closure was stronger than that of jasmonate. We discuss herein the relationship between ABA, jasmonates, and drought stress.
We investigated the effects of the size of seedling container used in the nursery (deep or shallow types) and of the nursing period (25, 30, or 35 days) on the growth and flowering of snapdragon (Antirrhinum majus L.) cv.‘Maryland Pink’ and‘Light Pink Butterfly II’. Snapdragons were seeded in July and pinched in September. We compared the results with those of the conventional method (temporary planting) for raising seedlings. Plant growth and subsequent yields of cut flowers increased in the deep containers. In seedlings raised for 35 days, plant height and the number of nodes decreased at the time of pinching, and the number of days from pinching to flowering of the second-node shoots increased. Flowering of the second-node shoots of plants with non-temporary planting occurred earlier than in the conventional method, and the yield of cut flowers was greater. To nurse the seedlings without temporary planting, planting within 30 days seems to be suitable regardless of the seedling containers that are used.
The allelopathic potential of an aqueous methanol extract of Citrus junos leaves was investigated under laboratory conditions. The extract inhibited the growth of roots and shoots of cress (Lepidium sativum L.), lettuce (Lactuca sativa L.) and alfalfa (Medicago sativa L.) seedlings. Significant reductions in the root and shoot growth were observed as the extract concentration increased. Since abscisic acid -β-D-glucopyranosyl ester (ABA-GE) was found to be a major inhibitor in fruit peel of C. junos, ABA-GE in C. junos leaves was determined and the concentration was 540 μg kg-1 fresh weight in the leaves harvested on September 26, 2002. These results suggest that C. junos leaves possess allelopathic activity and could work as a weed inhibiting agent, which should be investigated further in the field for practical application.
For production of high-quality St. John's wort (Hypericum perforatum L.) transplants, several authors have proposed in vitro multiplication of a superior germplasm by clonal propagation followed by ex vitro acclimatization in the greenhouse with natural light. This ex vitro acclimatization is a vital stage for successful transplant production. However, few studies have attempted to determine the optimum conditions for ex vitro acclimatization under artificial light. The objective of the current study was to find the necessary duration of ex vitro acclimatization by gradually reducing relative humidity under controlled environments with artificial light for St. John's wort plantlets grown photomixotrophically (sugar-containing medium) and photoautotrophically (sugar-free medium) in vitro. The results showed that all Photoautotrophically- and photo-mixotrophically-grown plantlets survived after the ex vitro acclimatization. Plantlets grown photoautotrophically in vitro were most suitable acclimatized to ex vitro environments by decreasing the relative humidity from 90 to 65% within two days. Meanwhile, the results suggested that plantlets grown photomixotrophically in vitro were most suitable acclimatized to ex vitro environments within four or seven days.