Search Results

You are looking at 1 - 10 of 19 items for

  • Author or Editor: Peter Hicklenton x
  • Refine by Access: All x
Clear All Modify Search
Free access

Jason Tutty and Peter Hicklenton

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

Jason Tutty and Peter Hicklenton

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

Peter R. Hicklenton

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

Peter R. Hicklenton and Kenneth G. Cairns

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

Peter R. Hicklenton and Kenneth G. Cairns

Free access

Peter R. Hicklenton and Kenneth G. Cairns

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

Peter R. Hicklenton and Julia Y. Reekie

In northern regions, strawberry nursery plants are often dug in the late fall, packed and stored for winter, and shipped to markets in the early spring. Success depends on identifying when plants are dormant and can be safely stored. Beginning on 11 Oct., plants of Kent and Veestar were dug at weekly intervals from three fields in the Annapolis Valley, N.S., Canada. At each digging date root respiration was measured at 5, 10, 20 and 30°C. Six “first daughter” plants of each cultivar were wrapped in plastic and placed in ≈1.5°C refrigerated storage. Other plants were separated into roots and leaves for carbohydrate analysis. Fall temperatures were relatively mild with 417 crown chilling hours (8°C base) accumulated to 7 Nov. Only those plants dug on 11 Oct. did not survive when planted to the field on 1, June but vigor (number of daughters/runners) improved for plants dug later in the fall. For Kent, vigor increased through the last digging date (5 Dec.), but for Veestar, vigor did not change after 7 Nov. Early dug plants had relatively high rates of root respiration, low concentrations of leaf and root glucose, fructose, sucrose, and raffinose and high leaf starch, and low root starch concentrations. Most leaf sugar concentrations increased rapidly after 7 Nov., and root starch reached a maximum at the same date. Leaf and root carbohydrate concentrations were correlated with poststorage field vigor and may reflect the degree of plant dormancy at time of digging.

Full access

Peter Havard, Leonard J. Eaton, and Peter R. Hicklenton

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.

Free access

Will G. Neily, Peter R. Hicklenton, and David N. Kristie

Experiments were conducted to determine the effects of treatment with gibberellic acid (GA) on changes in diurnal growth rhythms caused by maturation and day/night temperature differential (DIF) in zinnia (Zinnia elegans Jacq. `Pompon'). Plants were treated with GA3 or with the GA biosynthesis inhibitor daminozide under three DIF regimes (+5 DIF: 21 °C DT/16 °C NT; 0 DIF: 18.7 °C constant; –5 DIF: 16.5 °C DT/21.5 °C NT), each with a daily average temperature of 18.7 °C, at two developmental stages: stage 1, the period of vegetative growth before flower bud formation; and stage 3, growth just before anthesis. Instantaneous stem elongation rates (SER) were measured using linear voltage displacement transducers. The DIF regime, as has been previously shown, influenced stem elongation primarily by altering the size of an early morning peak in SER; peak height increased as DIF became more positive. GA3 increased SER throughout the diurnal period with a proportionately larger effect on nighttime growth. Conversely, daminozide decreased SER more or less equally throughout the diurnal period. Neither GA3 or daminozide transformed growth patterns to match those of positive or negative DIF plants, but instead simply increased or decreased growth amplitude. Furthermore, neither growth regulator altered the basic diurnal SER pattern at any DIF, or influenced the observed shift to greater nighttime growth as plants matured from stage 1 to stage 3. The results suggest that neither the effects of DIF, or the age-related shift in diurnal growth distribution can be explained by changes in total availability of GA in the plant. Chemical name used: mono (2,2-dimethylhydrazide) butanedioic acid (daminozide).