In class demonstrations, it is almost impossible to maintain the same water: air ratio in growing media. If some treatments result in greater plant growth than others, treatment effects on plant growth are often confounded with the effect of water: air ratio in the growing media. In a laboratory demonstration of nutrient deficiencies symptoms in plants, a controlled water table irrigation system maintained a constant water: air ratio in the growing media regardless of the nutrient deficiency affect on plant growth. The modified capillary mat irrigation system consists of one mat edge extending over the edge of the bench into a narrow trough on the side of the bench. The nutrient solution level in the trough is controlled by a liquid level controller, so it is at a fixed distance below the bench surface. The nutrient solution is drawn upward by capillarity to the bench surface and then moves by capillarity over the bench. The system automatically maintains a constant air: water ratio in the growing media. A standard Hogland solution was modified to demonstrate deficiencies in N, P, K, Mg, Ca, Cu, Fe, and Zn on corn, squash, radish, soybeans, and marigold. Seeds were germinated and grown to maturity in either a 10- or 15-cm pot. Students set up the demonstration, were provided instruction in preparing solutions, regularly observed plant growth, and answered questions at the end of the study about differences in plant growth observed. However, possibly because low concentrations of some minor elements in the capillary mat, Zn deficiency was not observed and other elements, although resulting in poor growth compared to the control, did not show severe deficiency symptoms.
The controlled water-table irrigation (CWT) system was evaluated for vegetable seed germination and transplant growth. The system is a modification of capillary mat irrigation except that the mat along one side extends over the edge of the bench into a narrow trough running along the side of the bench. The nutrient solution level in the trough is controlled by a liquid level controller, so it is at a fixed distance below the bench surface. The nutrient solution is drawn by capillarity from the trough upward to the bench surface and then moves by capillarity to the opposite side of the bench. The system automatically maintains a constant air: water ratio in the growing media. Seeds of broccoli, tomato, and pepper were germinated in a 96-cell plug tray and grown to transplanting stage with the CWT system. A factorial experiment consisted of two growing media combined with CWT treatments of 2 and 4 cm. Excellent germination and high-quality seedlings were produced with all treatments. No differences were observed in growth of seedlings at 2 vs. 4 cm or between the two growing media. The CWT system is capable of maintaining a constant uniform water: air ratio in all plug cells on a commercial growing bench. Nutrient solution does not run off the bench. The CWT potentially is an excellent system for the irrigation of vegetable transplants.
(2-Chloroethyl)phosphonic acid (ethephon) applied as a foliar spray on field-grown Hydrangea macrophylla 2 weeks prior to cold storage caused defoliation within 8 to 9 days. Complete defoliation occurred at 1000 to 5000 ppm of ethephon spray on both ‘Merveille’ and ‘Rose Supreme’. Ethephon-treated plants showed reduced height after subsequent forcing in the greenhouse. ‘Merveille’ was more sensitive to ethephon spray carry over than ‘Rose Supreme’. Optimum concentration range for defoliation and height reduction without any visible detrimental phytotoxic symptoms was 1000 and 2000 ppm for ‘Merveille’ and 1000 to 3000 ppm for ‘Rose Supreme’. Ethephon at 3000 ppm or higher on ‘Merveille’ and 5000 ppm or higher on ‘Rose Supreme’ induced abnormal yellow pigmentation of the flowers.
Students in plant science courses have difficulty thoroughly understanding the effect of water stress on net photosynthesis and its consequences—reduced plant growth, productivity, quality, and profit. A laboratory demonstration utilizing a controlled water table irrigation system (CWT) provides a nearly constant plant water potential. Pots are placed on a capillary mat with one end suspended in a trough with nutrient solution. The vertical distance from the solution surface to the pot bottom determines the water potential; the water potential is 0 when the pot bottom is at the same level as the nutrient solution. The greater the vertical distance from solution to the pot bottom, the lower the water potential. For this demonstration, the bench was sloped from 0 to 10 cm above the solution over a distance of 90 cm. Corn, squash, soybean, fescue, and marigold seed were directly sown to either 9- or 15-cm pots and then placed on the CWT sloped bench at five vertical distances above the solution. Weekly, students observed plant growth and at the end of 8 weeks evaluated root and shoot growth. For all species, plant growth was indirectly related to the distance above the nutrient solution. Plants at near 0 water potential were much larger than those grown 8 to 10 cm above the solution.
An analysis of using an air-earth heat exchange for controlling the environment in a greenhouse was conducted. For purpose of the analysis, a small greenhouse (2.75 m wide and 4.25 m long) connected to 30.5 m of 45 cm diameter pipe was assumed. In terms of heating, the air-earth heat exchanges proved to be inadequate except for the very southern parts of the United States, and even in these locations the temperature had to be limited to a relatively cool temperature of 10°C. A similar analysis for summer showed that the air-earth heat exchange could effectively limit the occurrence of high temperatures in a greenhouse throughout the United States.
Effectiveness of α-cyclopropyl α-(p-m ethoxyphenyl)-5 pyrimidinemethanol (ancymidol) drench, (2-chloroethyl-trimethyl ammonium chloride (chlormequat), drench or encapsulated, and (2-chloroethyl)phosphonic acid (ethephon), drench or granular, were compared on Euphorbia pulcherrima Willd. cvs. White Hegg and Dark Red Hegg. The most effective chemicals in terms of height control, improved foliage quality, size of bracts were 0.5 mg ancymidol (drench), 3000 ppm chlormequat (drench), 1250 ppm ethephon (drench) and 2.0 to 7.0 g ethephon (granulated).
Foliar application of 5% and 10% alkaryl polyoxyethylene glycol (X–77) surfactant to greenhouse forced pre-cooled ‘Georgia’ Easter lilies resulted in flower bud abortion and shorter plants. No phytotoxic effects were observed following application of 5% X–77 and only slight curving of young leaves were noted with 10% X–77 when applied to plants after 60 or more leaves had unfolded. There was no decrease in leaf number or damage to leaf area.
Tomato and pepper seedlings were grown in six controlled environmental chambers with three different temperature levels (high:24/16°C, medium:20/12°C, and low:16/8°C) and two CO2 levels (1500 ppm and ambient) after cotyledons had unfolded. After 4 weeks, seedlings were planted into 15 cm pots. After 4 weeks, another set were transplanted to the field on 5/13 and arranged with 4 replications in a randomized complete block design. Only temperature treatment had a significant influence on the number of flowers developed in greenhouse experiments. However, for field transplanted seedlings, CO2 enrichment had a significant effect on flower formation and increased total flower numbers and fruit numbers in the early growth stages in field. Temperature also influenced seedling height. In other experiments, cold treatments were given to tomato and pepper seedlings. Seedlings were treated with 13°C temperatures for 0, 1 or 2 weeks after cotyledons unfolded. Results indicate that tomato seedlings with either 1 or 2 weeks of cold treatment had greater dry weight and leaf numbers and larger and more mature flower buds than those given no cold treatment. Pepper seedlings receiving 2 weeks of cold treatment showed similar increases compared to those receiving 0 or 1 weeks of cold treatment. The earliest flower initials were observed microscopically when tomato had only one visible leaf and pepper had 8 or 9 visible leaves. These results indicate that cold treatments should be started as soon as the cotyledons have unfolded to hasten flower formation.
The surfactant alkaryl polyoxyethylene glycol containing free fatty adds and isopropanol (X -77) destructs apical meristems on Chrysanthemums morifolium Ramat: and shows potential for chemical pruning at concentration of 3.5 to 4%.
Two varieties of tall bearded iris, ‘Color Carnival’ and ‘First Violet’, were grown at minimum temperatures above 20° F throughout the fall and winter months. Groups of these plants were transferred periodically to a 65° house where they received either long or short-day treatments. Plants of ‘Color Carnival’ flowered under long days, regardless of the length of the vernalization period; under short days, some flowering occurred if the plants received more than 8 weeks of vernalization. Plants receiving 16 or more weeks of vernalization flowered equally well under long days or short days. Plants of ‘First Violet’ did not flower under flowering did not occur until the plants had long days unless the plants had received 16 or more weeks of vernalization; under short days received 20 or more weeks of vernalization. The longer the plants had been held at the minimum temperature, the shorter the time required for flowering after being transferred to 65°.