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Harry W. Janes, Seenithamby Logendra, and Sitheswary Logendra

It was proposed to study and develop a system for producing salad vegetables on a space station. To this end a `Salad Machine' was designed to act as a controlled environment growth chamber within which various plants will be grown on a continuous and predictable basis such that crew members will periodically have available the ingredients of a “normal” salad. Within this framework we studied the enclosed environment production of tomatoes.

Forty-five tomator cultivars were screened in a greenhouse and four were selected for further evaluation. The criteria for selection were total plant yield, fruit size, fruit quality and the total weight of the fruit on the main stem as compared to the axillary branches. The four selected cultivars were grown in an environmentally controlled chamber (`Salad Machine') at 6 plants/m (volume rather than area is important here). The data collected included: weekly plant height, total daily yield, water use and nutrient uptake.

The continuous production of tomatoes in a small volume using a selected cultivar will be discussed.

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Harry W. Janes and Richard J. McAvoy

In this paper we review our research of light effects on tomato production. It was demonstrated that, during the production of greenhouse tomatoes, the total fruit yield, as well as time of harvest, was related to light. The date of harvest was inversely correlated with the amount of light the crop received during the seedling phase of growth, while fruit weight was positively correlated with light during the production phase. Additionally, we present information that shows that light was most effective in promoting fruit development between 15 and 45 days after flowering. Some of these relationships were quantified and used to develop a predictive model to help a grower plan a tomato crop to meet market demand. The concept of the Single-cluster Tomato Production System was developed, and the rewards of using our understanding of plant-environment interactions to control plant growth and, therefore maxim&profits were shown. Furthermore, the need to create a more dynamic model and the methods for doing so were discussed.

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Han Ping Guan and Harry W. Janes

Light/dark effects on growth and sugar accumulation in tomato fruit were studied on intact plants (in vivo) and in tissue culture (in vitro). Similar patterns of growth and sugar accumulation were found in vivo and in vitro. Fruit growth in different sugar sources (glucose, fructose or sucrose) showed that sucrose was the primary carbon source translocated into tomato fruit. Darkening the fruit decreased growth about 40% in vivo and in vitro: Light-grown fruit took up 30% more sucrose from the same source and accumulated almost twice as much starch as that in dark-grown fruit. The difference in CO2 exchange rate between light and dark indicated that light effects on fruit growth were due to mechanisms other than photosynthesis. Supporting this conclusion was the fact that light intensities ranging from 40 to 160 μmol/m2/s had no influence on growth and light did not increase growth when fruits were grown on glucose or fructose. A possible expansion of an additional sink for carbon by fight stimulation of starch synthesis during early development will be discussed.

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Seenithamby Lgogendra, Harry W. Janes, Harry Motto, and Gene Giacomelli

With the increasing establishment of greenhouses in conjunction with resource recovery projects (i.e., producing electricity by burning a low cost fuel), greenhouse facilities have access to low cost heat and in many cases electricity as well. In this regard we have been studying the production of spinach with the use of supplemental light.

The goal of the research was to establish the relationship between light and productivity and to also investigate the effects of light on tissue nitrate levels. The data indicate that an average daily PPF of 13-14 moles will provide enough energy to maximize the plant's relative growth rate. It was also found that supplemental HPS light with a PPF of 90 μmoles/m2/sec given over a 12h period will increase the total light received by a plant in mid-winter by about 50% and lead to a 10% decrease in leaf nitrate level.

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Sitheswary Logendra, Mei-Mann Hsueh, and Harry W. Janes

Growing tomato fruits in tissue culture, using ovaries, could be used as a model system to study fruit development and sink strength/activity. Producing a “normal and healthy” fruit is essential in developing this system. Many factors affect the growth and development of the fruit. The objective of this study was to investigate the effect of the age of the ovary (i.e., the number of days after pollination) on growth and final fruit size. The results indicate that the fruit size, root development, and uniformity in growth of the fruit were affected by the initial age of the ovary. The older the ovary, the greater was the final fruit size and uniformity. The development of root mass was not affected by the age of the ovary until 7 days of pollination. However, root development was suppressed in ovaries that were of 9 days after pollination. The fruits from younger ovaries were more irregular in shape. All the fruits from ovaries harvested at 9 days after pollination were more uniform and round as compared to other treatments.

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Sitheswary Logendra, Mei-Mann Hsueh, and Harry W. Janes

The effect of root mass on tomato fruit size in tissue culture was studied. The root mass of the ovaries was changed either by growing in culture media containing different concentrations of NAA (α– napthaleneacetic acid) or by culturing the ovaries with and without sepals. The root mass increased with a decrease in NAA concentration from 10.0 to 2.5 μM and the ovaries with sepals developed more roots. The tomato fruit size was affected by the root mass. The greater the root mass, the larger was the fruit size. However, the larger fruit size from ovaries cultured with sepals could be attributed either to the presence of more roots (greater absorption of sucrose) or to the sepal (additional carbon fixation by photosynthesis), or to both the sepals and more roots. Moreover, it is possible that the presence of sepals induce root development. These results indicate that the presence of sepals and total root mass are two important factors that influence the fruit size in vitro.

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Logan S. Logendra, Thomas J. Gianfagna, and Harry W. Janes

Rockwool is an excellent growing medium for the hydroponic production of tomato; however, the standard size rockwool blocks [4 × 4 × 2.5 inches (10 × 10 × 6.3 cm) or 3 × 3 × 2.5 inches (7.5 × 7.5 × 6.3 cm)] are expensive. The following experiments were conducted with less expensive minirock wool blocks (MRBs), on rayon polyester material (RPM) as a bench top liner, to reduce the production cost of tomatoes (Lycopersicon esculentum) grown in a limited-cluster, ebb and flood hydroponic cultivation system. Fruit yield for single-cluster plants growing in MRBs [2 × 2 × 1.6 inches (5 × 5 × 4 cm) and 1.6 × 1.6 × 1.6 inches (4 × 4 × 4 cm)] was not significantly different from plants grown in larger sized blocks (3 × 3 × 2.5 inches). When the bench top was lined with RPM, roots penetrated the RPM, and an extensive root mat developed between the RPM and the bench top. The fruit yield from plants on RPM was significantly increased compared to plants without RPM due to increases in fruit size and fruit number. RPM also significantly reduced the incidence of blossom-end rot. In a second experiment, single- and double-cluster plants were grown on RPM. Fruit yield for double-cluster plants was 40% greater than for single-cluster plants due to an increase in fruit number, although the fruit were smaller in size. As in the first experiment, fruit yield for all plants grown in MRBs was not significantly different from plants grown in the larger sized blocks. MRBs and a RPM bench liner are an effective combination in the production of limited-cluster hydroponic tomatoes.

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Logan S. Logendra, Thomas J. Gianfagna, and Harry W. Janes

A mixture of C8/C10 fatty acid methyl esters (FAME) when applied directly and exclusively to leaf axils of greenhouse-grown tomato (Lycopersicon esculentum Mill.) significantly inhibited side shoot development. Plants grown in a single cluster production system in winter produced 8.9 side shoots/plant, whereas those treated with C8/C10 FAME 45 days after sowing, produced only 0.7 side shoots/plant. Total pruning weight of the side shoots was reduced from 40.2 g/plant to 1.3 g/plant. Fruit yield increased 14% with C8/C10 FAME treatment and there was an increase in the harvest index from 0.63 to 0.70. For a spring crop, in which average daily irradiance was more than twice that in winter, overall yield increased 70% when compared to the winter crop. As in winter, side shoot number and side shoot weight/plant were significantly reduced by C8/C10 FAME, but there was no difference in crop yield between C8/C10 FAME and untreated plants. In both winter and spring, untreated plants required hand pruning three times during the production period, whereas C8/C10 FAME-treated plants were pruned only once at the time of application. A C8/C10 free fatty acid (FA) mixture was also applied to one and two-cluster plants with similar results. In the multiple cluster system, application of the C8/C10 FA mixture instead of side shoot pruning reduced plant height and increased yield from 6.4 to 7.4 kg/plant. C8/C10 FA or C8/C10 FAME treatment could be a useful labor saving strategy in greenhouse tomato production and may increase crop yield under conditions in which assimilates may be limited by environmental factors, or as a result of a high level of competition from other fruits or shoots.

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Logan S. Logendra, Thomas J. Gianfagna, David R. Specca, and Harry W. Janes

Limited-cluster production systems may be a useful strategy to increase crop production and profitability for the greenhouse tomato (Lycopersicon esculentum Mill). In this study, using an ebb-and-flood hydroponics system, we modified plant architecture and spacing and determined the effects on fruit yield and harvest index at two light levels. Single-cluster plants pruned to allow two leaves above the cluster had 25% higher fruit yields than did plants pruned directly above the cluster; this was due to an increase in fruit weight, not fruit number. Both fruit yield and harvest index were greater for all single-cluster plants at the higher light level because of increases in both fruit weight and fruit number. Fruit yield for two-cluster plants was 30% to 40% higher than for singlecluster plants, and there was little difference in the dates or length of the harvest period. Fruit yield for three-cluster plants was not significantly different from that of two-cluster plants; moreover, the harvest period was delayed by 5 days. Plant density (5.5, 7.4, 9.2 plants/m2) affected fruit yield/plant, but not fruit yield/unit area. Given the higher costs for materials and labor associated with higher plant densities, a two-cluster crop at 5.5 plants/m2 with two leaves above the cluster was the best of the production system strategies tested.

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Logan S. Logendra, Jonathan G. Mun, Thomas J. Gianfagna, and Harry W. Janes

Ethephon (2-chloroethylphosphonic acid) was applied to single cluster greenhouse tomato crops (1000 ppm) at the green mature stage of fruit development or when 35% of the plants had fruits at the breaker stage. Fruits were harvested at the pink stage. Untreated fruit were harvested from 95 to 116 days after sowing whereas fruit from the green mature ethephon treatment were harvested from 92 to 102 days, three days earlier and with a reduction in the harvest window from 22 to 11 days. Fruit treated with ethephon at 35% breaker were harvested at the same time as untreated fruit, but harvest was completed after only 12 days. Fruit yield from the green mature ethephon treatment was reduced by about 30%, but there was no significant difference in fruit yield as a result of ethephon treatment at 35% breaker. Fruit color, firmness and soluble solids were evaluated one and six days after harvest. Fruit firmness and soluble solids were unaffected by treatment; however, fruit from the ethephon treatments were significantly redder in color. In a second experiment, ethephon was applied at 500 or 1000 ppm when 100% of the plants had fruit at the breaker stage. Fruit were harvested over a 7-day time interval compared to untreated fruit that were harvested over 14 days, and there was a small but significant increase in fruit yield for the 1000 ppm treatment. Both ethephon treatments also increased fruit soluble solids. For limited cluster tomato production systems, ethephon is effective in reducing the harvest window without loss in postharvest fruit quality.