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  • Author or Editor: Peter Hicklenton x
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Abstract

Chrysanthemum × morifolium Ramat cv. Paragon plants were grown under supplemental irradiation from high-pressure sodium lamps during rooting, long day (LD), and short day (SD) production stages in all combinations. Plants which were rooted under supplemental irradiation had higher relative growth rates (RGR) and dry weight increments during that stage than nonirradiated controls. Supplemental irradiation similarly increased RGR and dry weight increments during LD and 5 weeks of SD. Root, top, and total dry weights at the end of the SD irradiation period showed a residual incremental effect of the LD treatment. Percentage of increases in dry weight increments due to supplemental irradiation were quite consistent between stages, whereas treatments had a greater effect on RGR during rooting and LD than during SD. The number of days to final harvest was reduced by supplemental irradiation during rooting and LD. The numbers of flowering stem breaks per pot, mean stem break length, and total plant dry weight were increased by supplemental irradiation at each stage. Those effects principally were additive. Flower dry weight per plant was increased significantly only by LD treatment. The benefits of supplemental irradiation during each production stage, and of combined treatments, are discussed in relation to operating costs.

Open Access

Abstract

Brickett isobutylidene diurea (IBDU), at 3.4 kg N/m3 in combination with either potassium muriate (KC1) or fritted potassium (K-frit) at 0.4 or 0.8 kg K/m3 in a sawdust-sphagnum peat medium, produced growth and visual quality in container-grown Juniperus horizontalis Moench cv. Plumosa Compacta equal to that of plants grown with weekly liquid fertilization (2.7 N and 2.2 g K/plant per week). Finer IBDU granules (ca 0.7 mm diameter) at either 1.7 or 3.4 kg N/m3 produced inferior quality plants and less seasonal growth. Tissue N remained fairly constant in 3.4-kg N/m3 brickett IBDU treatments throughout the season, but decreased steadily with both rates of fine granules. Tissue K was lower through the season with K-frit than with either a single (0.4-kg K/m3) or double (total 0.8-kg K/m3) application of K-muriate (KC1). Neither K rate nor source had a consistent effect on plant growth or quality over all sources and rates of IBDU.

Open Access

Abstract

Overwintering under microfoam thermoblanket resulted in high poststorage quality of container-grown Cotoneaster Dammeri C. K. Schneid, and Juniperus chinensis L. ‘Pfitzerana-Aureo’ in USDA plant hardiness zones 5a and 6a (1). Similar results were obtained for J. chinensis overwintered under white copolymer in zone 5, but severe damage was sustained by C. Dammeri since the covering did not maintain media temperature above the lethal point for this species. Storage under clear copolymer at both locations caused foliage damage which was severe in C. Dammeri and moderate in J. chinensis. Black poly storage caused severe foliage damage in all J. chinensis and C. Dammeri. Viburnum cassinoides L. overwintered without serious damage in all treatments.

Open Access

The rate of internodal extension of chrysanthemum (Dendranthema grandiflora Tzvelev. cv. Envy) under various temperature and photoperiod conditions was studied to determine whether reproducible diurnal patterns of growth existed and whether any such patterns conformed to an endogenous circadian rhythm. Stem growth was monitored continuously by means of linear displacement voltage transducers. At constant temperature and under 11 h light/13 h dark photoperiod, stem elongation followed a clearly defined pattern consisting of a peak in rate immediately after the dark to light transition and then a gradual decline until the start of the dark period. During darkness, elongation rate increased and reached a maximum approximately 8 hours after the light to dark transition. This pattern differed when light period temperature was either above or below dark period temperature, but these patterns were also highly reproducible. When plants were subjected to continuous light at constant temperature, the rhythm of stem elongation initially showed a periodicity of approximately 27 hours. After 2 or 3 diurnal cycles the rhythm was less distinct and the rate became essentially constant. Furthermore, the interruption of a long period of continuous light with a 13 h dark period did not restore the rhythm. These findings do not support the existence of an endogenous circadian rhythm of stem elongation. Diurnally-cued rhythms do, however, exist and can be modified by temperature.

Free access

The rate of internodal extension of chrysanthemum (Dendranthema grandiflora Tzvelev. cv. Envy) under various temperature and photoperiod conditions was studied to determine whether reproducible diurnal patterns of growth existed and whether any such patterns conformed to an endogenous circadian rhythm. Stem growth was monitored continuously by means of linear displacement voltage transducers. At constant temperature and under 11 h light/13 h dark photoperiod, stem elongation followed a clearly defined pattern consisting of a peak in rate immediately after the dark to light transition and then a gradual decline until the start of the dark period. During darkness, elongation rate increased and reached a maximum approximately 8 hours after the light to dark transition. This pattern differed when light period temperature was either above or below dark period temperature, but these patterns were also highly reproducible. When plants were subjected to continuous light at constant temperature, the rhythm of stem elongation initially showed a periodicity of approximately 27 hours. After 2 or 3 diurnal cycles the rhythm was less distinct and the rate became essentially constant. Furthermore, the interruption of a long period of continuous light with a 13 h dark period did not restore the rhythm. These findings do not support the existence of an endogenous circadian rhythm of stem elongation. Diurnally-cued rhythms do, however, exist and can be modified by temperature.

Free access

Leaf yellowing of Alstroemeria hybrida L. `Rio' and `Jacqueline', as measured by sphere spectrocolorimetry, was significantly delayed in vase life studies when the ends of cut stems were immersed in solutions of BAP or GA3 immediately following harvest. When BAP or GA3 was used alone at 50 mg·liter-1, foliage color and color intensity did not diminish during 14 days of storage in tap water. BAP and GA3 also showed interaction effects on leaf color, but little was gained by using combinations of chemicals. Chemical names used: 6N-benzylaminopurine (BAP); gibberellin (GA3).

Free access

Abstract

Supplemental photosynthetically active radiation (PAR; 77, 148 and 231 μmol s-1m-2) was provided to Chrysanthemum morifolium Ramat ‘Paragon’ during 14 days each of rooting (24 hr daily), long days (LD; 24 hr daily) or short days (SD; 9 hr daily) in a greenhouse. Crop growth efficiency (calculated as the ratio of the observed to potential dry weight gain) was highest under the 77 μmol s-1 m-2treatment during each stage and decreased markedly at higher irradiances. Relative growth rates were increased by all levels of supplemental PAR at each stage. The increases were proportionately smaller than the increase in total PAR in treatments above 77 μmol s-1m-2. Flower number, and flower and vegetative dry weight increased in response to 77 μmol s-1m-2 supplemental PAR, but increased irradiances had no further effect. Extension of the 77 μmol s-1m-2 treatment beyond rooting to LD significantly improved all traits over single stage treatments. Further extension into SD, however, was not beneficial.

Open Access

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.

Free access

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.

Open Access

Containerized Cotoneaster dammeri `Coral Beauty' and Forsythia `Northern Gold' were grown in a 2 bark: 1 peat: 1 sand (by volume) medium containing 5 kg·m–3 Nutricote 16N–4.4P–8.1K, Type 140, under four irrigation regimes: drip (DR; 20 min/day; two periods), overhead (OV; 90 min/day; two periods), overhead pulse (OP; 28 min/day; four periods), and subirrigation (SU). Volumes of 0.33, 0.35, and 0.14 liters·day–1 were delivered to each container in the DR, OV, and OP systems, respectively. SU was supplied from a geotextile-covered sand bed. End-of-season dry weights of Cotoneaster and Forsythia were 41% and 55% greater, respectively, in SU-grown plants compared to their OV-irrigated counterparts. Differences in growth between the other three regimes were minor for both species. Pre-dawn and dusk water potentials did not differ between plants in the four regimes, but midday potentials were slightly lower in SU- and DI-irrigated plants. End-of-season foliar N and P content differed only slightly between irrigation treatments, but K levels were significantly higher in SU plants. The reasons for better growth under SU remain obscure but may be related to improved medium nutrient retention and improved fertilizer use efficiency under an irrigation regime in which water moves upwards from the pot base to top.

Free access