Night Interruption Treatments Research Articles

Propagation and Subsequent Growth of Rhododendron Cuttings: Varied Response to CO2 Enrichment and Supplementary Lighting

Abstract CO2 mist (1100 μl CO2/liter) during fall propagation inhibited rooting of Rhododendron ‘Anna Rose Whitney’ (R. griersonianum × ‘Countess of Derby’) and had no effect on R. ‘Vulcan’ (‘Mars’ × R. griersonianum), R. ‘Unique’ (R. campylocarpum hybrid), R. ‘Anah Krushke’ (R. ponticum seedling), or R. ‘Pink Bountiful’ (R. williamsianum × ‘Linswegeanum’). Supplementary lighting from high-pressure sodium lamps (HPS) for 16 hr/day (0400 to 2000 hr) had no effect on rooting of any cultivar. There was an interaction between CO2 mist and HPS exposure on rooting in R. ‘Floriade’ (‘Britannia’ hybrid). CO2 mist inhibited and HPS stimulated shoot development during propagation. CO2 mist during propagation inhibited subsequent development of ‘Anna Rose Whitney’ and ‘Vulcan’. HPS during propagation inhibited subsequent growth of ‘Floriade’ and ‘Vulcan’. CO2 enrichment of stock plants prior to propagation did not affect rooting of R. ‘Sonata’, whereas CO2 mist during propagation was inhibitory. In ‘Anna Rose Whitney’, there was an interaction between CO2 enrichment before and during propagation. Application of supplementary HPS for 16 hr/day following propagation stimulated subsequent growth of both cultivars. CO2 mist during spring propagation stimulated rooting of ‘Pink Bountiful’ and ‘Vulcan’ and had no effect on R. ‘Matador’ (R. griersonianum × strigillosum), R. ‘Martha Isaacson’ (R. occidentale × Ostbo seedling No. 70), or R. ‘Elizabeth’ (R. forestii var repens × griersonianum). Supplementary HPS had no effect on rooting. A low irradiance night break treatment from incandescent lamps (2000 to 0400 hr) had no effect on rooting of ‘Vulcan’. There was an interaction between night break lighting and CO2 mist on rooting in ‘Unique’. CO2 mist and HPS during spring propagation had minor effects on subsequent growth of ‘Matador’, ‘Martha Isaacson’, ‘Pink Bountiful’, and ‘Elizabeth’. CO2 mist and supplementary HPS have little value in production of Rhododendron.

Production of the Australian native daisies (Helipterum roseum and Helichrysum bracteatum) for the cut flower market

Cut flower production of 2 Australian native daisies, Helipterum roseum and Helichrysum bracteatum, was investigated in the glasshouse and outdoors at 4 planting times. Both species exhibited a long day response with floral initiation occurring in any photoperiod but with peak production following longer days. Peaks in bloom production occurred during the spring and summer regardless of planting time. Floral abnormalities were observed in Helipterum roseum in all environments and planting times with the exception of the outdoor winter planting. There was a tendency for inflorescence diameter of both species and stem length of Helipterum roseum to decline with time from anthesis of the apical inflorescence. Optimum production of top quality blooms of Helipterum roseum extended from October to January following planting between autumn and spring. Peak production of Helichrysum bracteatum between December and March can be expected following planting during winter and spring. It may be possible to extend these seasons by weekly planting from autumn to spring. In addition, the imposition of extended photoperiod or night break treatments following summer or autumn planting may fulfil the photoperiod requirements of the plants and stimulate increased production between March and November. It is proposed that both species be considered for the fresh cut flower market, with Helipterum roseum marketed as single stems and Helichrysum bracteatum as sprays.

Effect of Extended Photoperiod on Budbreak, Overwinter Survival, and Carbohydrate Levels of Acer rubrum ‘October Glory’ Rooted Cuttings

Abstract Acer rubrum L. ‘October Glory’ cuttings taken on 15 June 1984 were subjected to short day (SDT) (800-1700 HR) or short day plus night interruption treatments (NIT) (800-1700 plus 2200-200 HR) from 25 July until 22 Oct. 1984. Additional cuttings taken on 14 Aug. were subjected to the same photoperiod treatments from 10 Sept, until 22 Oct. For the 15 June cuttings, the NIT treatment induced significantly greater percent budbreak than the SDT, but did not induce significantly greater overwinter survival. Cuttings of 15 June that broke bud under NIT had significantly greater stem length and dry weight than cuttings that broke bud under SDT. SDT and NIT cuttings of 15 June that broke bud had significantly greater percent root carbohydrates, total grams of carbohydrates, and percent overwinter survival then cuttings that did not break bud. For the 14 Aug. cuttings, 1% of the cuttings broke bud, yet 95% (SDT) and 90% (NIT) of the cuttings survived the winter, and no difference in cutting carbohydrate levels, except stem starch, existed between the two treatments.

THE EFFECT OF PHOTOPERIOD ON AXILLARY BRANCH DEVELOPMENT AND FLOWER PRODUCTION OF A NEW GUINEA Impatiens HYBRID

The influence of photoperiod and temperature on the production of flowers by a New Guinea hybrid Impatiens, cv. Starburst, was investigated. Delayed flowering below 20 °C was due only to effects on flower bud development. Although flower initiation was day-neutral, the number of flowers produced was significantly influenced by photoperiodic control of axillary branch elongation. In 8-, 14- or 16-h photoperiods axillary branches on the lower nodes remained compact but in a 12-h photoperiod the axillary branches elongated, and flower production on these axillary branches was enhanced. Night-break (NB) treatments indicated that this was a photoperiodic effect. This photoperiodic control of plant growth habit provides a means of regulating the rate of flowering of this cultivar.Key words: Impatiens, photoperiod, flowering, apical dominance

LIGHT QUALITY AND STEM GROWTH IN IMPATIENS PARVIFLORA DC.

SummaryInternode and hypocotyl elongation were measured in Impatiens parviflora DC. in light environments in which extra far‐red light was mixed with white light from fluorescent tubes during the photoperiod and at the end of the photoperiod. Night breaks of varying spectral composition were also given. The logarithmic rate constant of internode elongation was found to be linearly related to the estimated proportion of phytochrome existing as the far‐red absorbing form. Supplementary far‐red light at the end of the day caused no significant increase in the elongation rate whereas night break treatments significantly increased the rate of internode elongation. Hypocotyl elongation was not related to the estimated phytochrome photo‐equilibrium and appeared to be under the control of both blue and red light. The results are discussed in relation to the hypothesis that the control of stem elongation by phytochrome is an adaptation for detecting and avoiding shade.

The Control of Flowering in Lilium longiflorum Thunb. cv. Nellie White by Cyclic or Continuous Light Treatments1

Abstract Flowering was accelerated by incandescent light day extensions of 3 minutes of light and 27 minutes of dark or longer light cycles and by 15 minutes of light and 15 minutes of dark cycles when BCJ-ruby incandescent light was given to young shoots from non-vernalized bulbs. If bulbs were vernalized for 3 weeks, cool white fluorescent light accelerated flowering as a day extension. As a night interruption, incandescent, fluorescent or BCJ-ruby incandescent cyclic light treatments accelerated flowering of shoots from vernalized or non-vernalized bulbs. Day extensions of cyclic fluorescent or BCJ-ruby light treatments of 6 minutes on and 24 off or 3 minutes on and 27 off did not mediate a phytochrome controlled flowering response and along with the fact that there was no photoreversibility between day extensions of incandescent, fluorescent or BCJ-ruby incandescent light, indicate a high energy reaction involvement in the flowering of the lily. As a night interruption treatment, a phytochrome mediated flowering response was observed with 3 minutes of light on and 27 off or 6 minutes on and 24 off cyclics of fluorescent or BCJ-ruby incandescent light treatments. However, as the light period increased to 15 minutes on and 15 off or under a continuous light cycle, there were no differences in the flowering response between fluorescent or BCJ-ruby incandescent. As night interruptions there was a reversibility response by R — FR, but not by FR — R. This indicated the simultaneous operation of the phytochrome and the high energy reaction.

Effects of Night Breaks on Floral Initiation and Development in Saccharum1

The effects of night breaks with light of different spectral compostion applied at various stages of floral development, starting before induction up to inflorescence emergence, were studied in Saccharum spontaneum L. and S. robustum L. clones. Night interruption treatments with incandescent light decreased % inflorescence emergence and delayed flowering when applied at all stages of development in S. spontaneum L. In both S. robustum L. and S. spontaneum L. clones, the degree of inhibition of flowering depended on the stages of development at which the night interruptions were applied; the early stages of differentiation of the inflorescence (initiation of inflorescence axis and branch primorda) were found to be the most sensitive. The spectral composition of the light used was also important; red, orange, and green light were generally the most inhibitory to inflorescence development, while blue, far‐red, and ultraviolet were not effective and similar to darkness. Attempts to reverse the inhibitory effect of red light by far‐red failed. Night breaks also had their maximum inhibitory effects when applied towards the end of the dark period and had minimum effects when applied at the middle of the dark period.

Minimum Number of Short Days for Production of High Quality Standard Chrysanthemums1

Abstract Natural daylengths in summer at 38°N latitude are partially inductive for Chrysanthemum morifolium, Ramat. cvs. Albatross and Escapade. This is indicated by the number of nodes to the terminal bud in natural daylength compared to a night break treatment. One week of short days (SD) is enough to fully satisfy induction of the terminal bud as expressed by the number of nodes to flower. Three to four weeks SD are ample for the development of high quality flowers equal to those grown under continuous SD; there was no significant delay in flowering.

Some effects of light and nutrition in the forcing of strawberries

SummaryStrawberry plants were allowed to initiate flower buds out-of-doors, then transferred to artificially illuminated cabinets for forcing. The yield of fruit was found to be independent of the nutritional treatments given (balanced, low nitrogen, high potash) but was highly dependent on the lighting regime, long days giving more fruit than short days or short days plus a night break.All the light given was from white fluorescent tubes and the night break treatment did not promote the long-day effects that might have been expected, possibly because there was insufficient far-red radiation for phytochrome synthesis.

Effects of Night-break Treatment on Leaf Area and Leaf Dry Weight in Callistephus chinensis

Effects of Night-break Treatment on Leaf Area and Leaf Dry Weight in Callistephus chinensis