Acta Horticulturae

Published by International Society for Horticultural Science
Online ISSN: 0567-7572
Publications
Article
The simultaneous and discriminative measurement of the photosynthesis and the respiration of the plant was attained by simultaneous monitoring of 13CO2 and 12CO2 by artificial control of 13CO2 abundance of ambient air. The principle of the measurement is based on the following physiological processes. 6CO2 + 12H2O --> C6H12O6 + 6O2 + 6H2O, 6(13C)O2 + 12H2O --> (13C6)H12O6 + 6O2 + 6H2O, 6CO2 + 12H2(18O) --> C6H12O6 + 6(18O)18O + 6H20. Assuming that respiratory consumption of the new born carbon substrate fixed by photosynthesis is negligible during the measurement, the photosynthetic CO2 consumption VPCO2 and the respiratory CO2 production VRCO2 are measured according to the estimation (1) or (2), (1) for closed method, VPCO2 = k(V0 - V t)¿ F13CO2 + (F12CO2/F13CO2)F13CO2 ¿, VRCO2 = k(V0 - V t)¿ F12CO2 - (F12CO2/F13CO2)F13CO2 ¿, (2) for open method, VPCO2 = kVE ¿ (FI13CO2 - FE13CO2) + (F12CO2/F13CO2)(FI13CO2 - FE13CO2) ¿, VRCO2 = kVE ¿ (FI12CO2 - FE12CO2) - (F12CO2/F13CO2)(FI13CO2 - FE13CO2) ¿ where V0 is initial volume of growth chamber including attached flexible bag, FICO2 is the inlet or initial gas concentration of CO2 and FECO2 is the ambient gas concentration of CO2 in the chamber, V and VE are the sampling rate of mass spectrometer and the ventilation rate of the growth chamber respectively, k is the STPD conversion factor = ¿273(PB-PH2O)/760(273+tE)¿, tE(degrees C) is the ambient gas temperature. In the closed method, the gas container of the growth chamber is circulated, resulting FECO2 is varied according to the balance of consumption and production of CO2, while in the open method VE is controlled to keep FECO2 at a constant value. Both (1) and (2) methods were examined and evaluated on the measurements of komatsuna and maize.
 
Article
We researched effects of diurnal change of the mineral concentration on tomato yield and nutrient absorption. First, we examined the effect on yield in a spray culture, in the experiment 1-1, when nitrate concentration of solution (N) and potassium concentration (K) were low and phosphate concentration (P) was high during the daytime, while N and K were high and P was low during the night, the yield was low. In the experiment 1-2, when N and K were high and P was low during the daytime, while N and K were low and P was high during the night, the yield was low. Second, we examined the effect on nutrient absorption in a water culture. Concentration of KNO3, of solution was changed in the daytime or the night. When KNO3 level was low during the daytime, while it was high during the night, total nitrate and potassium absorption for 24 hours was the highest. It were showed the possibility of the efficient supply of minerals to plants by the diurnal control in minerals.
 
Article
The production system for grafted seedlings mainly consists of three processes; 1) growth of seedlings, 2) grafting of seedlings, and 3) acclimation of grafted seedlings. Of the three processes, the duration of acclimation is highly influenced by the acclimation conditions. The acclimation environment after grafting was controlled to be satisfied the demands of grafted seedlings in the point of the physiological reaction such as photosynthesis, respiration, transpiration, and translocation nutrients. In the present study, a preliminary experiment was conducted to understand the relationship between the factors concerned with the acclimation of grafted seedlings, using a new acclimation apparatus. The factors of interest were air temperature, relative humidity, light, and carbon dioxide concentration. In the presence of light, the air temperature and relative humidity were interfered each other, so that both factors were difficult to keep at a constant value. Furthermore, the concentration of carbon dioxide was remarkably fluctuated by the relative humidity regulated by the humidifier and dehumidification which was controlled by the temperature differences between water and ambient air. A new device of acclimation system which is automatically controlled would be expected to construct in near future. Such a device will make it possible to shorten the duration of acclimation and produce high quality of grafted seedlings.
 
Article
In the development of a plant growth model, the assumptions made and the general equations representing an understanding of plant growth are gradually refined as more information is acquired through experimentation. One such experiment that contributed to sweetpotato model development consisted of measuring biomass accumulation of sweetpotato grown in hydroponic culture in a plant growth chamber. Plants were started from fifteen centimeter long 'TU-82-155' sweetpotato vine cuttings spaced 25 cm apart in each of 18 rectangular growing channels (0.15 by 0.15 by 1.2m) in a system designed to use the nutrient film technique (NFT). Each channel contained four plants. The 3.5m by 5.2m plant growth chamber environmental parameters included an 18h photoperiod, 500 micromoles m-2 s-1 of photosynthetic photon flux (PPF), and a diurnal light/dark temperature of 28 degrees C/22 degrees C. The relative humidity was 80 +/- 5% and the CO2 partial pressure was ambient (350 ppm). The nutrient solution contained in 30L reservoirs was a modified half Hoagland's solution with a 1:2.4 N:K ratio and a pH of 6.2. Solution replenishment occurred when the electrical conductivity (EC) level dropped below 1050. Plants were harvested at 15 days after planting (DAP) and weekly thereafter until day 134. By 57 DAP, stems and fibrous roots had acquired 90% of their total dry biomass, while leaves had reached 84% of their maximum dry biomass. Beginning at 64 DAP dry biomass accumulation in the storage roots dominated the increase in dry biomass for the plants. Dry weight of storage roots at 120 DAP was 165 g/plant or 1.1 kg/m2. Resulting growth curves were consistent with the physiological processes occurring in the plant. Results from this study will be incorporated in a plant growth model for use in conjunction with controlled life support systems for long-term manned space missions.
 
Article
Space missions of extended duration are currently hampered by the prohibitive costs of external resupply. To reduce the need for resupply, the National Aeronautics and Space Administration (NASA) is currently testing methods to recycle solid wastes, water, and air. Composting can be an integral part of a biologically based waste treatment/recycling system. Results indicate that leachate from composted plant wastes is not inhibitory to seed germination and contains sufficient inorganic minerals to support plant growth. Other solid wastes, for example kitchen (food) wastes and human solid wastes, can be composted with inedible plant residues to safely reduce the volume of the wastes and levels of microorganisms potentially pathogenic to humans. Finished compost could serve as a medium for plant growth or mushroom production.
 
Article
It is known that chlorophyll has the second distinct absorption peak in the vicinity of 450nm (blue light region) other than the first peak in the vicinity of 660nm (red light region) in its light absorption spectrum The blue light is also indispensable to the morphologically healthy growth plant. On the other hand, the red light contributes to the plant photosynthesis. Noticing this facts, we have developed various kind of plant growth apparatus using many pieces of blue light LED and red light LED with emission wavelength 450nm and 660nm as artificial light source. In this paper, we introduce our LED plant growth apparatus and systems named such as LED PACK, BIOLED, UNIPACK, and COMPACK with respect to their structure, function, electrical design, and characteristics.
 
Article
A plant growth chamber equipped with a machine vision (MV) system was developed for the continuous, non-contact sampling and near-real-time evaluation of the top projected leaf area (TPLA) of lettuce (Lactuca sativa, cv. Ostinata) seedlings. A rotary table enabled automatic, individual presentation of the lettuce plants to the imaging system. Hourly measurements were continuously made for 16 plants from the first true leaf stage through 30 days from seeding. A near-infrared radiation source illuminated the plants during the dark period, permitting measurements without interrupting the 12 hour photoperiod. Daily minimum hourly change of TPLA for the plants occurred from 3 to 4 hours after the start of the light period. Most rapid increase in TPLA occurred from 4 to 5 hours after the onset of the dark period. The machine vision system was capable of determining a plant physiological response to the nutrient stress within 24 hours of the change of the nutrient regime.
 
Article
Recycling waste products during orbital (e.g., International Space Station) and planetary missions (e.g., lunar base, Mars transit mission, Martian base) will reduce storage and resupply costs. Wastes streams on the space station will include human hygiene water, urine, faeces, and trash. Longer term missions will contain human waste and inedible plant material from plant growth systems used for atmospheric regeneration, food production, and water recycling. The feasibility of biological and physical-chemical waste recycling is being investigated as part of National Aeronautics and Space Administration's (NASA) Advanced Life Support (ALS) Program. In-vessel composting has lower manpower requirements, lower water and volume requirements, and greater potential for sanitization of human waste compared to alternative bioreactor designs such as continuously stirred tank reactors (CSTR). Residual solids from the process (i.e. compost) could be used a biological air filter, a plant nutrient source, and a carbon sink. Potential in-vessel composting designs for both near- and long-term space missions are presented and discussed with respect to the unique aspects of space-based systems.
 
Article
To clarify the possibility of plant production under red and blue monochrome light using light emitting diodes (LEDs), the effects of light quality and photosynthetic photon flux (PPF) on the growth and morphogenesis of lettuce plants were examined. Lettuce plants were hydroponically grown for 20 days, under 3 different light qualities (Red, Blue and Red/Blue) and 2 PPF levels (about 85 and 170 micromoles/m2/s) for a l6hr day and an 8hr night cycle, at a temperature range of 20 to 22 degrees C. Irrespective of the two different PPF levels, the plants grown under the red LEDs developed more leaves than the plants under the blue LEDs, but less leaves than the plants under blue/red light. The curvature rate of the leaf margin in the plants grown under the blue LEDs was less than that of the plants under red LEDs on both PPF levels. The inclination angle of the seventh leaf in the plants grown under the blue LEDs and the blue/red fluorescence lamps was greater than that of the plants under red LEDs on the high PPF level. The whole plant dry weight was greater in the plants grown under the high PPF level than the plants under a low PPF level.
 
Article
The superimposed pattern of "luminescence spectrum of blue light emitting diode (LED)" and "that of red LED", corresponds well to light absorption spectrum of chlorophyll. If these two kinds of LED are used as a light source, various plant cultivation experiments are possible. The cultivation experiments which use such light sources are becoming increasingly active, and in such experiments, it is very important to know the distribution of the photosynthetic photon flux (PPF) which exerts an important influence on photosynthesis. Therefore, we have developed a computer simulation system which can visualize the PPF distribution under a light source equipped with blue and red LEDs. In this system, an LED is assumed to be a point light source, and only the photons which are emitted directly from LED are considered. This simulation system can display a perspective view of the PPF distribution, a transverse and a longitudinal section of the distribution, and a contour map of the distribution. Moreover, a contour map of the ratio of the value of the PPF emitted by blue LEDs to that by blue and red LEDs can be displayed. As the representation is achieved by colored lines according to the magnitudes of the PPF in our system, a user can understand and evaluate the state of the PPF well.
 
Article
A layered canopy model was used to analyze the effects of diffuse light on canopy gross photosynthesis in controlled environment plant growth chambers, where, in contrast to the field, highly diffuse light can occur at high irradiance. The model suggests that high diffuse light fractions (approximately 0.7) and irradiance (1400 micromoles m-2 s-1) may enhance crop life-cycle canopy gross photosynthesis for hydroponic wheat by about 20% compared to direct light at the same irradiance. Our simulations suggest that high accuracy is not needed in specifying diffuse light fractions in chambers between approximately 0.7 and 1, because simulated photosynthesis for closed canopies plateau in this range. We also examined the effect of leaf angle distribution on canopy photosynthesis under growth chamber conditions, as these distributions determine canopy extinction coefficients for direct and diffuse light. We show that the spherical leaf angle distribution is not suitable for modeling photosynthesis of planophile canopies (e.g., soybean and peanut) in growth chambers. Also, the absorption of the light reflected from the surface below the canopy should generally be included in model simulations, as the corresponding albedo values in the photosynthetically active range may be quite high in growth chambers (e.g., approximately 0.5). In addition to the modeling implications, our results suggest that diffuse light conditions should be considered when drawing conclusions from experiments in controlled environments.
 
Article
In order to estimate the effects of "global warming" on plants, the effects of carbon dioxide concentration (500 ppm or 1000 ppm CO2) and/or relative humidity (37% or 79% RH) on the growth and the transpiration of several C3 plants and a C4 plant (corn) were investigated by using artificially-lighted growth cabinets. The dry weight growths of all species, especially C3 plants, were accelerated by an elevated concentration of CO2, but were reduced, especially tomato and eggplant, by lowering RH. The leaf area growths of tomato and eggplant were accelerated by a high CO2, while those of all species were reduced by a low RH. A high CO2 increased net assimilation rates (NARs) more than relative growth rates (RGRs) of all species. It decreased leaf area ratio (LAR) due to a decrease in specific leaf area (SLA). A low RH decreased RGRs of all plants. while it affected NARs or LARs of some species. The partitioning of dry matter was insignificantly affected by CO2 or RH. Effects of CO2 on the transpiration rate were not observed clearly with C3 species, though a high CO2 decreased the transpiration of corn obviously. A low RH increased the transpiration rates of all species. From these results, the water use efficiencies of many plants, especially corn were kept at a high level by a high CO2 with a high RH condition. The interactive effects between CO2 and RH on the growth and the transpiration were insignificantly observed in these plants.
 
Article
The response of 'TI-155' and 'Georgia Jet' sweetpotato cultivars to elevated CO2 concentrations of 400 (ambient), 750 and 1000 micromoles mol-1 were evaluated under controlled environment conditions using the nutrient film technique (NFT). Growth chamber conditions included photosynthetic photon flux (PPF) of 600 micromoles m-2 s-1, 14/10 light/dark period, and 70% +/- 5% RH. Plants were grown using a modified half-Hoagland nutrient solution with a pH range of 5.5-6.0 and an electrical conductivity of 0.12 S m-1. Gas exchange measurements were made using infrared gas analysis, an open-flow gas exchange system, and a controlled-climate cuvette. Photosynthetic (Pn) measurements were made at CO2 ranges of 50 to 1000 micromoles mol-1. Storage root yield/plant increased with CO2 up to 750 but declined at 1000 micromoles mol-1. Storage root dry matter (DM) and foliage dry weight increased with increasing CO2. Harvest index (HI) for both cultivars was highest at 750 micromoles mol-1. The PPF vs Pn curves were typical for C3 plants with saturation occurring at approximately 600 micromoles m-2 s-1. CO2 concentration did not significantly influence net Pn, transpiration, water-use-efficiency (WUE), and stomatal conductance. As measurement CO2 concentration increased, net Pn and WUE increased while transpiration and stomatal conductance decreased.
 
Dietary quercetin reduced (P < 0.06) expression of COX-1 by 20.2%. Values are means of saline and AOM-injected rats (n = 20/diet).  
Rats consuming diets without quercetin had elevated (P < 0.058) COX-2 expression (24.3%). Values are means of saline and AOM-injected rats (n = 20/diet).  
Article
We have demonstrated that 0.45% quercetin added to a diet containing corn oil (15% w/w), as the lipid source, and cellulose (6% w/w), as the fiber source, was able to suppress the formation of high multiplicity aberrant crypt foci (ACF > 4 AC/focus), to lower proliferation and enhance apoptosis in a rat model of colon cancer. This experiment determined whether quercetin was acting as an antiinflammatory molecule in an in vivo model of colon cancer. We used weanling (21 d old) Sprague Dawley rats (n = 40) in a 2×2 factorial experiment to determine the influence of quercetin on iNOS, COX-1 and COX-2 expressions, all of which are elevated in colon cancer. Half of the rats received a diet containing either 0 or 0.45% quercetin, and within each diet group, half of the rats were injected with saline or azoxymethane (AOM, 15 mg/kg BW, sc, 2× during wk 3 and 4). The colon was resected 4 wk after the last AOM injection, and the mucosa scraped and processed for RNA isolation. Data from this experiment were analyzed using a mixed model in SAS for main effects and their interaction. AOM injection stimulated (P < 0.0001) iNOS expression. However there was an interaction such that, relative to rats injected with saline, AOM-injected rats consuming diets without quercetin had significantly elevated iNOS expression (5.29-fold), but the expression in AOM-injected rats consuming the diet with quercetin was not significantly elevated (1.68-fold). COX-1 expression was 20.2% lower (P < 0.06) in rats consuming diets containing quercetin. COX-2 expression was 24.3% higher (P < 0.058) in rats consuming diets without quercetin. These data suggest inflammatory processes are elevated in this early stage of colon carcinogenesis, yet quercetin may protect against colon carcinogenesis by down-regulating the expressions of COX-1 and COX-2.
 
Article
A new dynamic control of photosynthetic photon flux (PPF) was tested using lettuce canopies growing in the Minitron II plant-growth/canopy gas-exchange system. Canopy photosynthetic rates (Pn) were measured in real time and fedback for further environment control. Pn can be manipulated by changing PPF, which is a good environmental parameter for dynamic control of crop production in a Controlled Ecological Life-Support Systems CELSS. Decision making that combines empirical mathematical models with rule sets developed from recent experimental data was tested. With comparable yield indices and potential for energy savings, dynamic control strategies will contribute greatly to the sustainability of space-deployed CELSS.
 
Article
The present Spacetron is used to cultivate plants over a long term by controlling environment condition. The cultivation drum was rotated in perpendicular direction creating fluctuation in gravity. Centrifugal force plus 1 G ground gravity, are distributed unevenly over the cultivation drum. This fluctuation effect on plant growth was not clear. In the modified Spacetron the cultivation drum rotates horizontally whereas the plant stage rotated in the perpendicular direction. To find the basic information for design of centrifugal phytotron the two axes Spacetron Junior (clinostat) was developed to formulate the micro and hypergravity environment. It would be used to study the effect on a plant growth process of different gravity conditions. In order to produce the different values of gravity, the clinostat's axis was rotated with a stepping motor at different angular velocity. The axis rotated at 5.2 revolutions per minute (rpm) to create a centrifugal force equivalent to 0.01 G and the plant stage was rotated at 5.2 rpm. The chlorophyll value is higher in the plants under microgravity condition of 0.01 G whereas the fresh weight and dry weight are higher in the plants under control condition of 1 G earth gravity. The result of this study showed that the plant growth was affected by microgravity along with other known factors such as vibration and unknown factors.
 
Article
To obtain the basic data of gas exchange of rice (Oryza sativa L. cv. Nipponbare), rates of ethylene release, photosynthesis and transpiration of the rice plant were measured by using a closed-type chamber. Each rate increased until the heading stage and thereafter decreased. Ethylene release rate (E) gradually increased with day after seeding and rates of photosynthesis (P) and transpiration (T) did exponentially. At the heading stage, E, P and T were maximum and had values of about 2.0 mmol plant-1 h-1, 3.0 mmol plant-1 h-1 and 0.60 mol plant-1 h-1, respectively. E in the light period was 1.5-3 times as much as that in the dark period, whereas T in the light period was 5-6 times as much as that in the dark period. E of rice per plant was lower than those of lettuce and Brassica genera which were reported previously. Especially, the rate of rice was about one-tenth that of lettuce. However, when ethylene release rates were estimated on a growth area basis, the rate of rice was about half that of lettuce, and was more than those of Brassica genera.
 
Article
CO2 and water vapor fluxes of hydroponically grown wheat and soybean canopies were measured continuously in several environments with an open gas exchange system. Canopy CO2 fluxes reflect the photosynthetic efficiency of a plant community, and provide a record of plant growth and health. There were significant diurnal fluctuations in root and shoot CO2 fluxes, and in shoot water vapor fluxes. Canopy stomatal conductance (Gc) to water vapor was calculated from simultaneous measurements of canopy temperature (Tcan) and transpiration rates (Tr). Tr in the dark was substantial, and there were large diurnal fluctuations in both Gc and Tr. Canopy net Photosynthesis (Pnet), Tr, and Gc increased with increasing net radiation. Gc increased with Tr, suggesting that the stomata of plants in controlled environments (CEs) behave differently from field-grown plants. A transpiration model based on measurements of Gc was developed for CEs. The model accurately predicted Tr from a soybean canopy.
 
Article
A computer program was developed to study multiple crop production and control in controlled environment plant production systems. The program simulates crop growth and development under nominal and off-nominal environments. Time-series crop models for wheat (Triticum aestivum), soybean (Glycine max), and white potato (Solanum tuberosum) are integrated with a model-based predictive controller. The controller evaluates and compensates for effects of environmental disturbances on crop production scheduling. The crop models consist of a set of nonlinear polynomial equations, six for each crop, developed using multivariate polynomial regression (MPR). Simulated data from DSSAT crop models, previously modified for crop production in controlled environments with hydroponics under elevated atmospheric carbon dioxide concentration, were used for the MPR fitting. The model-based predictive controller adjusts light intensity, air temperature, and carbon dioxide concentration set points in response to environmental perturbations. Control signals are determined from minimization of a cost function, which is based on the weighted control effort and squared-error between the system response and desired reference signal.
 
Article
A more basic understanding of the microbial dynamics of closed, hydroponic cultivation systems is needed. We therefore initiated a study of the microbial community inhabiting the root environment, using phospholipid fatty acid (PLFA) profiles, and started to examine whether changes in the microbial population structure would result from the introduction of selected isolates of plant growth-promoting rhizobacteria (PGPR). Tomato were cultured in deep-flow systems with circulating nutrient solution. Bacteria were sampled from tomato roots at three locations, longitudinally, in the gutters of a control system and in two systems inoculated with PGPR. In the beginning of the gutters the PLFA profiles were similar in all systems, whereas the profiles differed in the gutter ends (following the direction of flow). In the control system, and in a treatment inoculated with two Gram-negative and one Gram-positive PGPR strain, the relative proportion of PLFAs characteristic to Gram-positive bacteria was highest at the end of the gutter. In a treatment inoculated only with a Gram-negative PGPR strain, the relative proportion of PLFAs characteristic of Gram-negative bacteria was highest at the end of the gutter. The results indicate a complex situation with different micro-environments distributed along the root mat. It can also be concluded that PLFA profiles may be useful tools in the study of the microbiology of closed hydroponic plant cultivation systems.
 
Article
Potato plantlets (Solanum tuberosum L. cv. Benimaru) were cultured in vitro for 20 days on a 10 ml MS agar medium under a magnetic flux density of 0 (control: Cont), 2, 4 or 6 mT (T=Wb m-2) in both upward and downward directions of magnetic field. Air temperature in the head space of the test tubes and photosynthetic flux density on the culture shelf were 25 +/- 1 degrees C and 38 micromoles m-2 s-1 respectively. The results showed that a magnetic flux density of around 4 mT had beneficial effects, regardless of the direction of magnetic field, on the growth promotion and enhancement of CO2 uptake of potato plantlets in vitro The direction of magnetic field at the magnetic flux densities tested had no effects on the growth and CO2 exchange rate.
 
Article
The optimum management of nutrient solution in soilless culture needs the accurate control of nutrient solution, especially in recycled soilless culture system. To keep the electrical conductivity (EC) of nutrient solution within the adequate range after application of combined fertilizers, theoretically derived EC prediction methods are required. In this study, the experimental EC prediction equation, an extended form of the Robinson and Stroke's theoretical equation only available for a binary electrolyte, was developed for predicting the EC of the nutrient solution containing many kinds of inorganic compounds. And the multilayer perceptron consisting of three layers with the back propagation learning algorithm was developed for EC prediction. It consists of nine variables in the input layer for the concentrations of seven macro elements, Na+ and Cl, and one variable in the output layer for the EC of nutrient solution. The predicted ECs by experimental model as well as neural networks for the nutrient solution were compared to the measured ones and showed good agreements.
 
Article
Sweetpotato is one of several crops recommended by National Aeronautics and Space Administration (NASA) for bioregenerative life support studies. One of the objectives of the Tuskegee University NASA Center is to optimize growth conditions for adaptability of sweetpotatoes for closed bioregenerative systems. The role of nutrient solution management as it impacts yield has been one of the major thrusts in these studies. Nutrient solution management protocol currently used consists of a modified half Hoagland solution that is changed at 14-day intervals. Reservoirs are refilled with deionized water if the volume of the nutrient solution was reduced to 8 liters or less before the time of solution change. There is the need to recycle and replenish nutrient solution during crop growth, rather than discard at 14 day intervals as previously done, in order to reduce waste. Experiments were conducted in an environmental growth room to examine the effects of container size on the growth of several sweetpotato genotypes grown under a nutrient replenishment protocol. Plants were grown from vine cuttings of 15cm length and were planted in 0.15 x 0.15 x 1.2m growth channels using a closed nutrient film technique system. Nutrient was supplied in a modified half strength Hoagland's solution with a 1:2.4 N:K ratio. Nutrient replenishment protocol consisted of daily water replenishment to a constant volume of 30.4 liters in the small containers and 273.6 liters in the large container. Nutrients were replenished as needed when the EC of the nutrient solution fell below 1200 mhos/cm. The experimental design used was a split-plot with the main plot being container size and genotypes as the subplot. Nine sweetpotato genotypes were evaluated. Results showed no effect of nutrient solution container size on storage root yield, foliage fresh and dry mass, leaf area or vine length. However, plants grown using the large nutrient solution container accumulated more storage root dry mass than those with the small containers. Although plants grown with the smaller containers showed greater water uptake, plant nutrient uptake was lower than with the larger container. All genotypes evaluated showed variation in their responses to all parameters measured.
 
Article
Providing a controlled environment for growth of plants in a space environment involves development of unique technologies for the various subsystems of the plant growing facility. These subsystems must be capable of providing the desired environmental control within the operational constraints of currently available space vehicles, primarily the US Space Shuttle or the Russian Space Station, MIR. These constraints include available electrical power, limited total payload mass, and limited volume of the payload. In addition, the space hardware must meet safety requirements for a man-rated space vehicle. The ASTROCULTURE (TM) space-based plant growth unit provides control of temperature, humidity, and carbon dioxide concentration of the plant chamber air. A light emitting diode (LED) unit provides red and blue photons with a total intensity adjustable from 0 to 500 micromoles m-2 s-1. Ethylene released by the plant material is removed with a non-consumable ethylene removable unit. A porous tube and rooting matrix subsystem is used to supply water and nutrients to the plants. The ASTROCULTURE(TM) flight unit is sized to be accommodated in a single middeck locker of the US Space Shuttle, the SPACEHAB module, and with slight modification in the SPACELAB module. The environmental control capabilities of the subsystems used in the ASTROCULTURE(TM) flight unit have been validated in a microgravity environment during five US Space Shuttle missions, including two with plants. The unique environmental control technologies developed for the space-based plant growth facility can be used to enhance the environmental control capabilities of terrestrial controlled environment plant chambers.
 
Article
The heat transfer characteristics of a hydroponic system were experimentally verified after theoretical establishment and the effect of nutrient solution cooling on the plant temperature was investigated. About 96 percent of the total heat flow transferred from culture bed to nutrient solution was the conductive heat through planting board and partitioning materials. The average and maximum temperatures of the leaf lettuce decreased 0.6 and 1.5 degrees C., respectively, with cooling of nutrient solution by 6 degrees C. A numerical model for prediction of cooling load of nutrient solution in a hydroponic greenhouse was developed, and the results from the simulation model showed a good agreement with those from experiments. A mechanical cooling system using the counter flow type with double pipes was developed for cooling the nutrient solution. Also the heat transfer characteristics of the system were analyzed experimentally and theoretically, and compared with the other existing cooling systems of nutrient solution. The cooling capacities of three different systems, which used polyethylene tube in solution tank, stainless tube in solution tank, and the counter flow type with double pipes, were comparatively evaluated.
 
Article
Thiobacillus ferrooxidans is a chemoautotrophic bacterium that is capable of using Fe2+ oxidation by O2 as the sole source of energy for growth and CO2 fixation. The idea of the solar bacterial biomass farm by using of this bacterium is proposed. The incubation experiment of these bacteria was carried out, and the 9K culture medium as the standard medium for T. ferrooxidans was used. The measurement of Fe2+ in the growth stage was carried out as the first step of the experiments to clarify the possibility of this system. The items of measurement were Fe2+ ion density, pH of the medium, bacterium density and quantity of total organic carbon (TOC). The density of Fe2+ ion in the medium was measured by coulometry method. This method has the following advantage, high accuracy (<1%), easy operation, short measurement time (a few minutes) and small sample quantity (about 0.1 ml). The experimental results show that the Fe 2+ ion density is measured as same as the accuracy of pH measurement. At the final stage of the growth, the pH decreased due to the generation of the iron hydroxide (Fe(OH)3). The bacterium density and TOC slightly increased after that Fe2+ runs short. This result shows that the CO2 fixation speed is slower than Fe2+ oxidation speed. It is shown by the experiment that the growth limit of T. ferrooxidans is caused by the disappearance of the Fe2+ ion. It may be possible that the bacterium density increases by the continuous supply of Fe2+ ion.
 
Article
As part of bioregenerative life support feasibility testing by NASA, crop residues are being used to resupply elemental nutrients to recirculating hydroponic crop production systems. Methods for recovering nutrients from crop residues have evolved from water soaking (leaching) to rapid aerobic bioreactor processing. Leaching residues recovered the majority of elements but it also recovered significant amounts of soluble organics. The high organic content of leachates was detrimental to plant growth. Aerobic bioreactor processing reduced the organic content ten-fold, which reduced or eliminated phytotoxic effects. Wheat and potato production studies were successful using effluents from reactors having with 8- to 1-day retention times. Aerobic bioreactor effluents supplied at least half of the crops elemental mass needs in these studies. Descriptions of leachate and effluent mineral content, biomass productivity, microbial activity, and nutrient budgets for potato and wheat are presented.
 
Article
Dissolved O2 concentration ([O2]) in nutrient solution was controlled at 0.01, 0.10 and 0.20 mM with accuracy of +/- 0.005 mM in a newly developed hydroponic system, and the effects of [O2] on water uptake and growth of cucumber plants (Cucumis sativus L.) were analyzed. For evaluating water uptake rate under the control of [O2], water flux at the stem base was measured on-line with +/-5% in accuracy, 1 mg s-1 in resolution and 1 min in time constant by heat flux control (HFC) method. Water uptake rate was drastically increased by lighting to the plant at each [O2], and water uptake per day was depressed in proportion to decrease in [O2]. In the plants grown for 10 days, leaf area, fresh weight and dry weight of leaves decreased at lower [O2], while stem length and number of leaves were scarcely affected. These facts suggest that membrane permeability of root cells reduces at lower [O2] through respiration-dependent processes, and growth is inhibited through leaf turgor loss caused by the depressed water uptake of roots in O2-deficient nutrient solution in hydroponics.
 
Some biologically active constituents of Hypericum perforatum.  
Examples of the dark (e.g. naphthodianthrone-containing) glands and canals found on petals (left) and the anther connective (right) in Hypericum perforatum (Photos: M. Azizi).  
Article
This research is part of an ongoing selection and breeding effort to target Iranian genotypes of Hypericum perforatum with the potential to produce higher amounts of desired secondary metabolites and greater resistance to fungal pathogens. There is a significant interest in the development of such cultivars to supply materials to the local pharmaceutical industries. For this reason, two improved cultivars of H. perforatum ("Gold" and "Veperikon") were compared with a wild Iranian population (Ardabile population) under common garden conditions in Iran. Plants were cultivated from seed in a greenhouse and seedlings were transplanted after one month to the field plots. The statistical design of this study was a Randomized Complete Block Design with three replications. During the period of full flowering, selected phenological (number of days to flowering), morphological (plant height, mean leaf area, number of black glands/leaf) and chemical (hypericin and pseudohypericin content) characteristics were assessed. Our observations were that the "Veperikon" cultivar is very sensitive to soil-borne diseases. All transplanted seedlings were infected by the plant pathogenic fungus Colletotrichum gloeosporioides, which caused necrosis of the whole plant. Both the "Gold" cultivar and plants from the wild population persisted despite mild infections with C. gloeosporioides and produced flowering shoots at both the first and second years after cultivation. The "Gold" cultivar was superior to the Ardabile population in terms of phenological and morphological characteristics. The average naphthodianthrone content (% dry weight of tissue) for the wild Iranian population was 0.04(±0.01)%, but for the "Gold" cultivar, 0.33(±0.43)%. These data indicate that selection and directed cultivation of Iranian H. perforatum plants can result in plants with improved morphological, phenological and chemical characteristics.
 
Article
Higher plants are being evaluated for life support to provide needed food, oxygen and water as well as removal of carbon dioxide from the atmosphere. The successful utilization of plants in space will require the development of not only highly productive growing systems but also highly efficient bioregenerative systems. It will be necessary to recycle all inedible plant parts and all human wastes so that the entire complement of elemental compounds can be reused. Potatoes have been proposed as one of the desirable crops because they are 1) extremely productive, yielding more than 100 metric tons per hectare from field plantings, 2) the edible tubers are high in digestible starch (70%) and protein (10%) on a dry weight basis, 3) up to 80% of the total plant production is in tubers and thus edible, 4) the plants are easily propagated either from tubers or from tissue culture plantlets, 5) the tubers can be utilized with a minimum of processing, and 6) potatoes can be prepared in a variety of different forms for the human diet (Tibbitts et al., 1982). However potatoes have a growth pattern that complicates the development of growing the plants in controlled systems. Tubers are borne on underground stems that are botanically termed 'rhizomes', but in common usage termed 'stolons'. The stolons must be maintained in a dark, moist area with sufficient provision for enlargement of tubers. Stems rapidly terminate in flowers forcing extensive branching and spreading of plants so that individual plants will cover 0.2 m2 or more area. Thus the growing system must be developed to provide an area that is darkened for tuber and root growth and of sufficient size for plant spread. A system developed for growing potatoes, or any plants, in space will have certain requirements that must be met to make them a useful part of a life support system. The system must 1) be constructed of materials, and involve media, that can be reused for many successive cycles of plant growth, 2) involve a minimum quantity of media, 3) contain media that is essentially inert and not oxidize or degrade with use, 4) utilize a recirculating nutrient solution to permit regulation of pH and nutrient concentrations, and 5) be capable of complete automation of all planting, maintenance and harvesting procedures.
 
Article
The effect of vapor pressure deficit (VPD) of air during photoperiod on spinach growth under low total pressure was examined. Spinach plants grown under atmospheric pressure were transplanted into a pressure-reduced growth chamber and cultured hydroponically for eight days. The air temperature in the growth chamber was kept at 25 degrees C during the light period and 20 degrees C during the dark period. In the control, the total pressure was 101 kPa and the VPD was 0.95 kPa. The low pressure treatment had a total pressure of 25 kPa and a VPD of 0.95 kPa. The low pressure and high humidity treatment had a total pressure of 25 kPa, and a VPD of 0.48 kPa. The VPD during the dark period was consistent for all treatments at 0.44 kPa. O2 and CO2 partial pressures were constant at 21 kPa and 40 Pa, respectively. The photosynthetic photon flux density (PPFD) on a plant bed inside the growth chamber was 250 micromoles m-2 s-1 on a plant bed. Relative growth rate (RGR) of spinach in the low pressure and high humidity treatment was significantly greater than in the control. There was no significant difference in RGR between the control and the low pressure treatment. The low pressure and high humidity treatment also had increased leaf area. These results showed that the effect of pressure alone was not significant on RGR, but the combination of low pressure with high humidity was important.
 
Article
Age-related macular degeneration (AMD) is the leading cause of irreversible visual loss in the developed world. This disease of the elderly robs them of central vision in one or both eyes leading to a devastating loss of the ability to drive, read, and recognize faces. In recent years, a number of novel treatments for the neovascular form of AMD (also known as "wet" or exudative AMD) have been introduced, and for the first time, the relentless downhill course of vision loss experienced by the majority of patients with this particularly malignant variant of AMD has been transformed to the stabilization and even improvement of vision in at least two-thirds of patients. Likewise, the slower, more insidious form of AMD known as dry AMD which leads to geographic atrophy of the macula has become the focus of pharmaceutical firms' efforts for intervention. Unfortunately, all of these novel treatments have limitations, and they tend to be very expensive. Thus, prevention of AMD is of paramount importance to reduce the healthcare burden of this blinding disorder. Accumulating evidence suggests that encouragement of increased consumption of fruits and vegetables rich in the xanthophyll carotenoids lutein and zeaxanthin is a simple, cost effective public health intervention that might help to decrease the incidence of AMD. In this review article, the scientific underpinnings for these nutritional recommendations will be surveyed.
 
Article
Stomatal frequency, length and width were studied in two determinate type soybean (Glycine max L. Merr.) cultivars at 15, 20 and 25 degrees C on 60th day after emergence. The stomatal frequency on the adaxial leaf surface did not show any consistent trend for the increase of growing temperatures but on the abaxial surface, stomatal frequency significantly decreased for every increase of 5 degrees C. Akishirome had 503, 454 and 379 stomata mm-2 and Akiyoshi had 471, 442 and 384 mm-2 at 15, 20 and 25 degrees C respectively. The stomatal lengths of both surfaces increased toward optimum temperature and were longer in the adaxial surface Maintaining this trend, the lengths varied between 16.3 to 23.4 micrometers on the adaxial surface and from 14.2 to 21.5 micrometers on the abaxial surface. Width of the whole stomatal apparatus at noon time did not show any significant variation due to environmental temperature. Net photosynthesis rate of 4th leaf from top significantly increased in higher temperatures in both cultivars and showed similar trend at 32nd day after emergence and on 62nd day after emergence. Stomatal conductance increased and dark respiration decreased with increasing temperature. Plants grown in 25 degrees C were transferred to 15, 20 and 30 degrees C temperature chambers. On the 30th day after emergence, 4 hours of treatment resulted similar significant effects on net photosynthesis (ranging between 12.55 and 31.37 micromoles CO2 m-2 s-1 in Akishirome, and between 16.26 to 34.53 micrometers CO2 m-2 s-1 in Akiyoshi). 72 hours of similar treatments at 60 day after emergence also produced identical results. Therefore, higher temperature increased stomatal size but decreased its frequency, and increased net photosynthesis and stomatal conductance.
 
Article
Lettuce (Lactuca sativa L., cv. Ostinata) growth experiments were carried out to study the effect of dissolved oxygen (DO) concentration on plant growth in a floating hydroponic system. Pure O2 and N2 gas were supplied to the hydroponic system for precise DO control. This system made it easy to increase the DO concentration beyond the maximum (or saturation) concentration possible when bubbling air into water. Eleven day old lettuce seedlings were grown for 24 days under various DO concentrations: sub-saturated, saturated, and super-saturated. There was no significant difference in fresh weight, shoot and root dry weights among the DO concentrations: 2.1 (25% of saturated at 24 degrees C), 4.2 (50%), 8.4 (saturated), and 16.8 (200%) mg/L. The critical DO concentration for vigorous lettuce growth was considered to be lower than 2.1 mg/L. Neither root damage nor delay of shoot growth was observed at any of the studied DO concentrations.
 
Article
A computer vision system was developed to analyze plant growth. The developed system has a great advantage that various shapes of plant can be applied without any modification of software. The system consisted mainly of CCD camera, image capture board, computer, infrared LED and mirror system, and was easily set up. The infrared LED was hooked onto the plant part which was the location to be measured. Images, containing both the plant and the LED, with the different angle were simultaneously obtained using the mirror system, digitized and stored into a magneto optical diskette at a fixed interval. The centroid value of the LED was computed from the stored images and determined as the LED location. Experiments were conducted to evaluate the newly developed system by analyzing the elongation rate of Verbena bonariensis L. The results were compared to that obtained by the former non-contact analyzing system and it was found that the new system was applicable to plant growth analysis. This approach can not be substituted for the non-contact analyzing system formerly developed because it is contact type. However, this system can be applied to various plants without any modification in software, and has a potential for a wide use.
 
Article
Primed spinach (Spinacia oleracea L., cv. Nordic) seed was started in rockwool slabs in a growth room for eight days before the seedlings were transplanted into a controlled environment greenhouse equipped with five identical, but separate, NFT systems. The day and night temperatures in the greenhouse were maintained at 24 and 18 degrees C, respectively, with the daytime starting at 06:00 and ending at 22:00 hr. A photoperiod of 16 hrs was maintained, to prevent early bolting, and different target daily integrated light levels (PPF, in mol m-2 d-1) were studied to observe dry weight production. HPS lamps were used as the supplemental light source. Thirty-three days after seeding a final harvest was performed. Using the expolinear growth equation, dry weight production can be predicted based solely on target daily integrated light levels. Total chlorine residuals in the nutrient solution higher than 1 ppm were observed to be toxic. Root disease (rot) in the plant crown was found to be caused by Fusarium. Several remedies, including three biofungicides and potassium silicate, were tried but none proved to be consistently successful.
 
Article
A closed gas-exchange system was developed to measure gross photosynthesis and respiration discriminately and simultaneously. The system developed in this study included a high performance mass spectral analyzer for gas measurements. The gas-exchange system consisted of a 3L assimilation leaf chamber, a 1L flexible metallic bag, gas supply apparatus, and a lighting system. The lights were turned on and gas measurements were started after the initial 12CO2 concentration level was increased to 500 ppm. The 13CO2 gas was added to the chamber 10 min after the start of the light period. The lights were turned off 15 min after the addition of 13CO2. The 12CO2 and 13CO2 concentrations in the chamber during the light and dark periods were measured for pothos and maize leaves. The 13CO2 absorption rate by the leaves was larger than that for 12CO2 during the light period. It was assumed that the 13CO2 absorbed by photosynthesis was not evoluted by respiration during the first 25 min from the start of the light period. Based on this assumption, gross photosynthetic rate and respiration rate were estimated by calculating the difference in uptake rates of 12CO2 and 13CO2 during the light period.
 
Article
Major shifts in world economy, society and technology will cause dramatic changes in Dutch horticulture and in the attitude of the government towards research. The horticulture industry will change from a production-driven to a customer-driven strategy while developing market-oriented product chains. More than ever, knowledge becomes a critical factor in competition. In contrast with the past, the horticulture industry will protect knowledge to increase its profitability. The government will choose to focus on basic sciences, leaving applied research mainly to the industry. This is a major shift since the government used to be responsible for most research. Complete institutional research programmes are no longer state-financed; instead, a system of financing research programmes by competitive bids is being developed. The government is also restructuring the infrastructure of agricultural research. Breakthroughs in science and technology will have strong effects on how the industry will develop. The more important ones are described. In the future, research institutes will act in a competitive environment with great uncertainties. The knowledge market used to be dominated by governments, but will be dominated by internationally active private enterprises. Both management and researchers will take more customer-oriented attitudes. Research institutes will need to develop strategies to survive under these circumstances. Some possibilities are discussed. It is concluded that horticultural research will change. Instead of focusing on plant production, it will include many more disciplines and multi-disciplinary collaboration in agreement to the information flow in product chains. The horticulture industry will have to decide whether separate horticultural stations for applied research should remain and what kind of work must be done in the future.
 
Chapter
To determine the effect of wide ranges of macronutrient fertilisation on leaf micronutrient concentrations and plant growth characteristics ‘Navaho’ blackberry, plants were grown in sand culture for two years and fertilised with solutions consisting of five macro nutrients (N, P, K, Ca, and Mg) applied at three different rates (0 mg/l, control and 10X control). Foliar samples were collected at 4, 8 and 16 weeks after treatment initiation during the second growing season. Leaf Fe was highest at recommended rates of all macronutrient fertilisations. Mn leaf concentrations were increased with increasing rates of Mg, but decreased with 10x rates of N and Ca. High concentrations of Zn were found in plants receiving 10x rates of P fertilisation. Leaf Cu was increased by increasing N or K, but was decreased by P, Ca or Mg. Toxicity and deficiency symptoms were more evident with the N, K, and Mg fertiliser treatments.
 
Purchasing frequency of the different gardening product groups by the young families (n=151) 
Comparison of the importance and satisfaction of selected purchase criteria in the three preferred places of purchase (applied the frequency of the two positive levels of a four-ranking-scale, n=104) 
Preferred places of purchase –groups tendencys' in the determined factors (n=83) * significant differential of means (SL=5%, ANOVA) 
Article
Paper prepared for presentation at the First Symposium on Horticulture in Europe (SHE), 17th to 20th February 2008 at Vienna/Austria held under the aegis of ALVA, APH, BNL-SHS, DGG, GSHS, IOH, INRA, NJF, PSHS, SECH, SOI and the International Society for Horticultural Science
 
Article
As with other areas of science, supply chain analysis suffers from the fact that practitioners of its different component disciplines often find it exchange results and methods of analysis. For fresh produce supply chains a key issue is how to unite the elegant mathematical work on the physiology of quality change with the more qualitative methods of social science that are applied to the analysis supply chain management. This paper explores the possibility of utilising approaches which are widely used in demography to unify concepts of quality modelling and supply chain efficiency in the fresh produce sector. A key feature of demographic (or karpographic) models is that they use the average properties of individuals to model the behaviour of cohorts (or batches) and thus have a direct means of including biological variance within their scope. We illustrate the potential of matrix projection models to provide a simple way to unite mathematical analyses of keeping quality and subjective and qualitative analyses of supply chain efficiency. Among other results, the paper demonstrates a rational basis for the assumption, which has been adopted in recent policy changes to the EU food and agriculture policy, that short (or local) supply chains are, ceterus paribus, superior to longer ones. The analytical approach suggested spans the gap between theoretical modelling and knowledge transfer in a single step and requires no more to allow parameterisation than the elicitation of subjective probability estimates from supply chain participants on the transition of produce from one quality class to another.
 
China's Horticultural Exports by Major Product Groups (% by value)
China's Rising Share of the Japan Fresh Flower Market
China's Fresh Apple Trade and Trade Competitive Index
Article
Summary Recent debate on the reasons for the informal sector has led to renewed focus on how to operationalize the measurement of informal employment. This paper investigates congruence between three empirical measures of the rate of informality using Brazilian household survey data for the period 1992-2004. Sixty-three percent of the economically active are informal according to at least one definition, but only 40% are informal according to all three. Regression analysis is used to shed further light on differences in these measures. Appropriate measurement is therefore of high significance to policy analysis and design of appropriate strategies to reduce informality.
 
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Article
Market gardening has been increasing fast in Senegal. But farmers face high marketing risks: daily price fluctuations exceed an average 20% for some products, seasonality is strong, anticipation based on prices leads to cyclic movements. Farmers and market operators have found various forms of coordination to manage uncertainty. “Coxers” are specifically dedicated to information gathering, either in rural or wholesale urban markets or to transport negotiation. Paid per unit handled, they limit their own risk, whereas they reduce uncertainty for their partners. In other cases, interlinked transactions permit to provide inputs to producers despite the deficient credit market; meanwhile, it secures merchants access to product. As it is the case in many other countries, information provided by MIS is of little help to Senegalese market gardeners. The updated and more targeted access to information through MANOBI services allows producers to improve their negotiation capacity. But it does not modify the existing coordination features, given that they are not only determined by needs in information (but also by social links, access to credit, payment modalities, transport facilities…).
 
Chapter
IntroductionBiology of the Highbush BlueberryGenetic Resources for Breeding Southern Highbush BlueberryOrigins of Highbush Blueberry BreedingMethods Breeding Objectives Recommending Cultivars for Commercial PlantingsOutlook and IssuesLiterature Cited
 
Article
Introduction Corona discharge has been reported to reduce the decay and extend the storage life of fruits and vegetables. Potential mechanisms by which the corona could affect produce quality include the destruction of ethylene and volatiles, removal of airborne fungal spores, and the production of ozone, negative air ions (NAI) and other reactive species. Ozone and/or NAI have been reported to inhibit or kill pathogenic microbes and reduce decay of fresh produce (Tanimura 1997, 1998). This study evaluated the efficacy of a commercially available corona generation system on produce decay. et al., Materials and Methods An assortment of produce was or was not inoculated with various pathogens and held in two "jacketed" chambers at 10 C and 9598 % RH. Disease development was monitored for up to 3 weeks. The treatment chamber contained a FletcherFresh FE6 air purification system (FE, Hudson, PQ, Canada) equipped with a single corona generating plate made o
 
Chapter
IntroductionAdvantages of Cut Flowers StorageFactors Affecting the Storage Life of FlowersStorage Methods Concluding RemarksLiterature Cited
 
Article
The U.S. Department of Agriculture - Agricultural Research Service (USDA-ARS), in cooperation with Oregon State University (OSU) and the Oregon Blueberry Trial Support Group, has been running an extensive selection and cultivar evaluation trial at the OSU North Willamette Research and Extension Center (NWREC) in Aurora Oregon. Since the initial planting in 1990, over 120 genotypes have been evaluated. Over the years, the evaluation approach has been streamlined and improved based on experience and data analyses. The very practical things that have been learned include: 1) netting is essential for evaluating genotypes ripening in June and July; 2) a randomized complete block design, while not as ideal as a completely randomized design for detecting genotypic differences, is better from a practical standpoint when managing the best way to add new genotypes to the planting; 3) three replications were sufficient to detect differences that were meaningful to growers, about 2.69 t/ha vs. 1.80 t/ha with five replications; and 4) good harvests in years 4, 5 and 6 after planting was highly correlated with performance of total yield over years 3-9. As far as blueberry type was concerned, northern highbush blueberries were well adapted to the NWES site but most southern highbush were not. The southern highbush, with the notable exception of 'Legacy' and 'Ozarkblue', grew well but tended to be very low yielding due in part to mid-winter flowering. Rabbiteye blueberries grew well although their fruit quality was generally poorer than highbush blueberries. Rabbiteye cultivars that overlap with the highbush ripening season are not of much interest, whereas cultivars like 'Powderblue', which has good quality and 'Ochlockonee' that is very late ripening have excellent potential for late-season markets.
 
Article
Opuntia has a long tradition of use for forage in Mexico,. Tunisia and arid regions of the US. The vast majority of these cacti are spineless as spiny forage types are more difficult to work with. Some spiny Opuntias are very cold tolerant existing as far as 56 N in Alberta, Canada. In contrast traditional spineless Opuntia ficus-indica species, normally used for fruits, are limited in extension to USDA cold hardiness zones 9 and 10 due to lack of cold hardiness. Discovery of a spineless cold hardy O. ellisiana adapted to USDA cold hardiness zone 7 has the potential to greatly expand the range for livestock forage. Additionally new crosses between spineless O ficus-indica and the cold hardy, but spiny Texas native O. lindheimerii have produced spineless progeny that are currently being evaluated for forage characteristics in USDA cold hardiness zone 7 and 8 in Argentina. USDA computer models have been used to predict where spineless Opuntia types could be used in semi-arid areas world wide in USDA cold hardiness zones 7 and 8.
 
Article
The plant quarantine measures for tulip and lily bulbs were abolished in 1988. A removal of the quarantine made Japanese bulb growers face international competition in the markets. Since then the imports of bulbs, mainly from Holland, increased rapidly and bulb prices tended to decline gradually, while the Japanese production of bulbs did not decrease. The imports also introduced new varieties of bulbs to Japan. The demand for tulip bulbs increased greatly until the late 1990s, but in the 2000s the Japanese bulb markets stagnated. Bulb prices decreased, and the domestic production of bulbs decreased sharply, which caused a great reduction in the number of bulb farmers. Consequently, the rate of self-sufficiency for producing tulip bulbs in Japan decreased from 80% in 1988 to 20 % in 2006, even though the volume of imported bulbs decreased in the 2000s. This paper analyzes the demand and supply conditions of tulip bulbs, and reports estimates of the Japanese demand and supply functions of tulip bulbs by regression analysis. Demand depends upon the real price (in terms of consumption goods) of tulip bulbs negatively and the real national income positively, and shows that the demand curve shifted forward until 2001, and then shifted backwards. Domestic supply depends upon the prices of tulip bulbs and the rice prices positively.
 
Top-cited authors
L.F.M. Marcelis
  • Wageningen University & Research
Guglielmo Costa
  • University of Bologna
T. Kozai
  • Chiba University
E. Heuvelink
  • Wageningen University & Research
Jaap M van Tuyl
  • Wageningen University & Research