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- Author or Editor: Peter Hicklenton x
Abstract
Butterhead lettuce (Lactuca sativa L. ‘Montana’) plants were grown in recirculating solution culture in growth chambers under various combinations of day temperatures (TD; 12°, 15°, 19.5°, or 22.5°C) and night temperatures (TN; 5° or 14°) and root-zone temperature (TR; 20°, 23°, 26°, or 29°) Photosynthetic photon flux (PPF) was 3.8 mol·day−1·m−2. Leaf area and weight were determined at 7-day intervals. The final harvest followed 28 days of treatments. There were no significant interaction effects between TD and TN. An increase of TD from 12° to 19.5° increased fresh and dry leaf weight and leaf area at final harvest, but increasing TN from 5° to 14° had little effect. Specific leaf area and leaf area ratio increased with increasing TD and TN. Leaf weight ratio increased with TD but remained constant with TN. The overall effect of TR on plant size was minor. Dry weight of roots decreased with increasing TR at the 14- and 21-day harvests, but fresh and dry leaf weights were not affected. Leaf area increased with TR up to 26°. Increases in TR resulted in increased values for specific leaf area, leaf area ratio, and leaf weight ratio at final harvest. The results suggest that some butterhead lettuce cultivars may be grown satisfactorily under low daily PPF by allowing TN to decline to 5° while maintaining TD at ≈ 19°C. In ‘Montana’, increasing TR above 20° under those conditions had little beneficial effect on plant size at harvest.
Nutrient release from Nutricote Type 100 (100-day N release; 16N-4.4P-8.1K), and from a 1:3 mixture of Nutricote Type 40 (40-day N release; 16N-4.4P-8.1K) and Type 100 was affected by time and temperature. The Type 40/100 mixture released nutrients more rapidly over a 5 to 35C range in laboratory studies. Seasonal growth of containerized cotoneaster (Cotoneaster dammeri C.K. Schneid `Coral Beauty') and juniper (Juniperus horizontalis Moench. `Plumosa Compacta') increased with increasing application rates of either Nutricote Type 100 or a 1:3 mixture of Type 40/100 over the range 2-10 kg·m-3. Between 25 June and 27 July, cotoneaster grew more rapidly in media with Type 40/100 Nutricote, but by the end of the season (27 Sept.), fertilizer type showed no effect on plant dry weight. Shoot N was higher in cotoneaster plants grown with Type 40/100 Nutricote than with the Type 100 formulation during the first 2 months of growth, reflecting the more rapid release and uptake of N from the mixture. During the last month the situation was reversed, as nutrients from the Type 40/100 mixture were depleted. Potassium and P shoot concentrations were not affected by fertilizer type. Juniper growth and shoot concentrations of N, K, and P were not affected by fertilizer type at any time during the season. The results provided no evidence that seasonal growth could be enhanced in either cotoneaster (grows rapidly) or juniper (slower growing) by mixing rapid and more slowly releasing types of Nutricote.
Capillary irrigation uses less water than most other methoes, and effectively reduces the quantity of fertilizer leaching from nursery containers. We have developed a sand bed system with automatic control of bed hydration using inexpensive and readily available analog hardware. Water supply to the sand bed (via irrigation drip hose) is controlled by a bridge-type temperature controller associated with two stainless steel mesh sensors embedded in the sand. Growth, quality and nutrient status of capillary (CI) or drip-irrigated (DI) Juniperus horizontalis `Plumosa Compacta'(Andorra juniper) and Euonymus fortunei `Coloratus' were compared in 2 consecutive growing seasons. At the end of the second year CI Juniper and Euonymus plants were 23% and 37% larger, respectively, than their DI counterparts. Foliar N did not differ between irrigation regimes in Juniper, but both P and K levels were higher in CI plants; foliar N, P, and K, were consistently higher in CI Euonymus.
Two commercial freezers were modified to provide an inexpensive chamber system to investigate frost effects on wild, lowbush blueberries (Vaccinium angustifolium) under field conditions. A computer control system was developed with software written in Visual Basic 6.0 for MSWindows, which precisely controlled temperature in the plant canopy when the chambers were placed over blueberry plants in the field. Frost events (with temperatures ranging from -2 to -15 °C (28.4 to 5.0 °F)) were simulated by user input to control the cooling and warming rates, and minimum temperatures. The system records temperature set points, and current temperature in the plant canopy, or elsewhere in the plant environment, and provides a graphical display of key parameters. Trials have verified the reproducability of temperature profiles and the chambers have been used to provide preliminary information on the effects of frost at bloom on fruit set and development.
Our previous work on modifying strawberry plant morphology used either mowing to remove the leaf laminas and part of the petioles on `Camarosa', or a new reduced-risk gibberellin synthesis inhibitor, Prohexadione-Ca (ProCa), to restrict cell elongation in `Sweet Charlie'. These early studies showed promising results in acheiving desirable plant size and increasing fruit yield in annual hill plasticulture. Therefore, in the growing seasons of 2001 and 2002, we used `Camarosa' to explore the possibility of combining mowing and ProCa as a means of modifying strawberry transplant morphology in the nurseries, and studied its effect on fruit production in annual hill plasticulture. Plants were mowed and treated with 62.5 μL·L-1 of ProCa in a nursery field in Nova Scotia (45°26'N, 63°27'W). Treatments consisted of either mowing, the application of ProCa, or a combination of mowing and ProCa on one of two dates, 5 or 19 Sept. ProCa application early in the growing season had increased the production of daughter plants in the nursery. All plants were harvested in early October, and immediately transplanted in Dover, Fla. (28°00'N, 82°22'W). Fruits were collected twice weekly from late November to February or March. At time of harvest, both mowing and ProCa reduced plant height and total leaf area; plants which were treated with ProCa and mowed were the shortest. On average, treated plants had higher fruit yield as compared to untreated plants. In 2001, early fruit production in December was increased significantly in treated plants.
Bare-root transplants received from high latitude nurseries for Florida production have limited root systems, very long petioles and wilt soon after planting. Further dessication occurs when leaves come in contact with black plastic mulch used in the annual production system. Conventional irrigation practices for the establishment of bare-root transplants of strawberry consist of overhead water application for at least 8 hours/day for 10-14 days after planting. Plant growth regulators (PGRs) have been used to modify the growth characteristics of many plants species. A split-block experiment was implemented at the GCREC-Dover, Dover Fla., to determine the effect of the use Prohexidione-Ca (PC) and IBA [(indole-3) butyric acid] on growth, yield and establishment of strawberry. Main blocks consisted of over head establishment irrigation for 4, 8, and 12 days, and sub-plots consisted of treatments of PC applied in the nursery at a rate of 62.5 mg·L-1 2, 4, or 6 weeks before digging, PC applied in the nursery at 31.25 mg·L-1 2 weeks before digging, a root dip of transplants in 100 mg·L-1 IBA just prior to transplanting. The experiment was conducted for four growing seasons. Data were recorded for marketable yield, number of marketable berries (>10g), and disease incidence. Significant differences were detected for duration of establishment irrigation and growth regulator treatment. No interaction was shown between establishment irrigation and growth regulator treatment.
The effects of night temperature (NT) and photosynthetic photon flux (PPF) on time to flower and flower yield in `Bristol Fairy' and `Bridal Veil' Gypsophila paniculata L. (perennial baby's breath) were studied in controlled environments. Plants were grown with nights at 8, 12, 16, and 20C and 450 or 710 μmol·s-1·m-2 photosynthetic photon flux (PPF). Days were at 20C. In both cultivars, the times from the start of treatments to visible bud and from visible bud to anthesis were delayed at the lower PPF and at an NT <20C. The delays in `Bristol Fairy' were greater than those in `Bridal Veil'. Failure of `Bristol Fairy' plants to reach anthesis was common at SC NT and either 450 or 710 μmol·s-1·m-2 PPF; whereas in `Bridal Veil', nearly all plants flowered, regardless of environmental conditions. Flower yield (measured as fresh weight of inflorescences) decreased with NT in `Bristol Fairy' but was highest at 8 or 12C in `Bridal Veil'. In a second experiment using the same cultivars, the effect of curtailing long-day (LD) conditions at various stages on stem elongation and flower yield was investigated. `Bristol Fairy' required more LD cycles (>56) than `Bridal Veil' for maximum stem elongation and flower yield. Terminating LD conditions before the start of inflorescence expansion resulted in lower yields and shorter plants in both cultivars.
Abstract
A hydroponic nutrient film (NF) system was compared with soil for the production of five cut chrysanthemum crops in a commercial greenhouse. Crops of the cultivars Polaris; Blue, White and Florida Marble; Icecap; Chardonnay; and Heirloom matured 5 days earlier, on average, in NF than in soil. Yields of flowering stems were similar in each system, but close spacing increased productivity per unit greenhouse area for NF. Costs and returns for installation and operation of soil and NF systems in a 1-ha greenhouse were analyzed based on data obtained from the trial crops. Capital and operating costs per unit area increased for NF, but productivity and returns were also greatly improved. Internal rates of return (IRR) were higher for NF, compared to soil, over economic lifetimes ranging from 5 to 25 years. Product price variations caused similar changes in IRR for both systems. A 20% downturn in price, however, resulted in IRR of 3.5% and 19.4% for soil and NF, respectively, over a 25-year lifetime.
Stem elongation rates (SERs) of `Giant Tetra' snapdragon (Antirrhinum majus L.) and `Pompon' zinnia (Zinnia violacea Cav.) were determined in three temperature regimes in which differentials had been established between day and night temperature. The differentials [expressed as day temperature - night temperature (DIF)] were +5 DIF, 21 °C day/16 °C night; 0 DIF, 18.7 °C constant; and -5 DIF, 16.5 °C day/21.5 °C night; daily average 18.7 °C. In each regimes SERs were determined for three developmental stages—vegetative, visible bud, and preanthesis. SER was measured in controlled-environment chambers under 13-hour day/11-hour night photoperiods using linear voltage displacement transducers. Snapdragon and zinnia displayed rhythmic patterns of growth with strikingly different characteristics. SER for snapdragon consisted of a large peak in growth at the day/night (D/N) transition followed by a minimum in SER at the night/day (N/D) transition. The pattern did not change through development. In contrast the SER pattern changed significantly in zinnia. At the vegetative stage, diurnal SER was dominated by a large peak after the N/D transition [an early morning peak (EMP)]. At the later growth stages, the EMP remained visible, but the proportion of growth occurring at night increased. SER was rhythmic in both species for a limited period in continuous light and constant temperature. Zinnia displayed a stronger endogenous rhythm of SER than snapdragon. In both species, only day period growth was affected by DIF. The size of EMPs in both species increased under positive DIF and decreased under negative DIF, resulting in the overall DIF effect on plant height (a progressive increase in total diurnal elongation as DIF increased from -5 to +5). Internode lengths for snapdragon and zinnia were similar for plants grown to full flower at constant 17, 20, or 23 °C (0 DIF), indicating that DIF—not average daily, night, or day temperature—is a major determinant of extension growth.
Winter greenhouse production of perennial baby's breath (Gypsophila paniculata L.) is hampered by short daylength, low PPF and low temperatures. Flowering of the popular cultivar `Bristol Fairy'(BF) can be improved by supplemental assimilation lighting, but the costs are rarely justifiable. `Bridal Veil' (BV) is a new cultivar with similar flower morphology to BF. BF and BV were grown under long day (LD) conditions at 8, 12, 16 and 20C night (20C day) and either 450 or 710 μmol s-1 m-2 in controlled environments. Most BF plants failed to lower at 8C in both PPF. Nearly all BV plants flowered irrespective of growth conditions. Flower yield decreased with night temperature in BF but was greatest at 8 or 12C in BV. BF required more LD cycles (>56) than BV for maximum stem elongation and flower yield. Termination of LD conditions before the start of inflorescence expansion resulted in reduced yields in all plants.