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Abstract

Poinsettias (Euphorbia pulcherrima Willd. cvs. Annette Hegg Supreme, V-10, and Brilliant Annette Hegg) were grown on heated benches and exposed to root zone temperatures between 18° and 29° C. Increasing media temperatures affected bract size and development, internode length, fresh and dry weight of stems, leaves, and bracts, as well as the number of axillary shoots of cultivars differentially. In general, plants grown at higher temperatures were shorter, had more prominent axillary shoots, and developed anthocyanin sooner than unheated controls.

Abstract

Poinsettias (Euphorbia pulcherrima Willd. cv. Annette Hegg Brilliant Diamond) were grown in separate greenhouses, one in which the night air temperature was maintained at 16.7°C and another where the air temperature was allowed to fall to 11.5°. The cool-air-treated plants were subjected to root-zone temperatures of 17°, 23°, 26°, and 29°. In general, the deleterious effects of cool air temperatures could be reversed by root-zone warming at 23°.

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.

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.

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.

Abstract

Various concentrations of salicylhydroxamic acid and alpha, alpha-dipyridyl (reported inhibitors of cyanide-insensitive respiration) applied to fruit of ‘Bose’ pear (Pyrus communis L.) reduced fruit softening. The application of silver ions, reported to inhibit ethylene action, delayed ripening.

Abstract

Acetaldehyde is produced in fruit of pear (Pyrus communis L.) and can stimulate ripening. The action of selective inhibitors indicates that acetaldehyde operates independently of ethylene.

Abstract

Tomato plants (Lycopersicon esculentum Mill. cv. Laura), pruned to a single-flower truss, were exposed to 90 μmol·s⁻¹·m⁻² supplemental photosynthetic lighting (0400 to 2200 hr) during the developmental period: a) anthesis to initial fruit set, b) anthesis to mature-green fruit, or c) anthesis to red-ripe fruit. The yield response was compared to plants receiving d) no supplemental photosynthetic lighting after incipient anthesis. The greatest increase in average fruit weight was produced with continued supplemental lighting during the developmental-period initial fruit set to the mature-green stage. Net photosynthetic activity, μmol CO₂/min per dm², was the greatest in the canopy during early anthesis and then steadily declined as the canopy aged. Net whole plant photosynthetic activity, μmol CO₂/min per plant, increased steadily after the early anthesis stage of development to a peak rate during the rapid fruit development stage. Net whole plant photosynthetic activity then declined as the plant approached the mature-green and then finally the red-ripe stage of fruit development.

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.

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.