Wook Oh

Flowering of cyclamen is accelerated by an increase in temperature, photoperiod, and daily light integral

Summary Cyclamen (Cyclamen persicum Mill.) crop production times can be reduced by increasing the greenhouse temperature, but alternative methods to accelerate crop development are desirable when energy costs for heating are high. The effects of photoperiod and increasing daily light integral (DLI) on cyclamen remain unclear. We performed experiments to examine the effect of DLI using two temperatures (16°C or 20°C) and three photoperiods (8, 12, or 16 h) delivering DLI values of 4.9, 7.3, or 9.8 mol m–2 d–1, respectively, and the effect of night interruption (NI) lighting from incandescent lamps (IL), on the flowering of cyclamen ‘Metis Purple Flame’. Plants grown at 20°C reached the visible flower bud (VB) stage earlier than plants grown at 16°C under all photoperiods. NI hastened flower bud initiation by 22 – 29 d compared with an 8-h photoperiod at both temperatures. Plants grown under the 8-h photoperiod with an NI treatment (DLI = 4.9 mol m–2 d–1) flowered at a similar time as plants grown under the 12-h photoperiod (DLI = 7.3 mol m–2 d–1). In addition, plants grown at 16°C with an NI reached the VB stage in a similar time to plants grown at 20°C with an 8-h photoperiod. Therefore, the effects of increasing the DLI, providing NI lighting, or increasing the temperature can be compared, so that growers can determine which strategies can reduce the greenhouse production time of cyclamen most cost-effectively.

Light intensity and temperature regulate petiole elongation by controlling the content of and sensitivity to gibberellin in Cyclamen persicum

This study was carried out to investigate the responses of cyclamen to gibberellic acids (GAs) and GA biosynthesis inhibitors under different temperature and light intensity during different period, and then to examine the changes in GA level and sensitivity to GA under these environmental conditions. ‘Metis Scarlet Red’ cyclamen plants with 15 fully unfolded leaves were grown under in three controlled environment chambers maintained at 16/12 (LT), 22/18 (MT), 28/24°C (HT) (day/night), respectively. In each chamber, there were growth modules which provided three photosynthetic photon fluxes (PPFs) [60 (LL), 120 (ML), 240 (HL) μmol∙m−2∙s−1] at canopy height with 16 hours (08:00–24:00) of photoperiod by fluorescent lamps. Exogenous GA3 and GA4+7 increased petiole length at all PPF and temperature treatments and the promoting effect was larger under higher PPF irrespective of temperature. But, daminozide and paclobutrazol inhibited petiole elongation rate and inhibition activity increased with decreasing PPF. GA3 nullified the inhibiting effect on petiole elongation by daminozide. However, there were significant differences in the elongation rate promoted and inhibited by GA3 and daminozide, respectively, between PPFs and temperatures. Promoting effects of GA3 on petiole elongation increased with decreasing PPF and increasing temperature.

Temperature and long-day lighting strategy affect flowering time and crop characteristics in Cyclamen persicum

Long-day treatments such as day extension (DE) and night interruption (NI) lighting during short day and cold seasons can promote the growth and flower development of Cyclamen persicum and cyclic NI lighting (CL) can reduce the lighting cost as compared with continuous NI. To compare the effect of CL with continuous NI or DE under different temperatures, cyclamen (Cyclamen persicum Mill.) ‘Metis Red’ was grown until full bloom at 12, 16, or 20°C during dark period in combination with six photoperiods: 9-hour short days (08:00–17:00) with natural sun light (SD), SD + 6-hour DE (17:00–23:00), SD + 2-hour (23:00–01:00) or 4-hour (22:00–02:00) NI, and 10% [6 min on and 54 min off (6/54) for 4-hour] or 20% [6 min on and 24 min off (6/24) for 4-hour] CL. Compact fluorescent lamps used as the light source delivered about 3 mol·m−2·s−1 PPFD at the canopy level. Plants grown at 20°C during the dark period had visible buds and open flowers earlier by 7 days than those grown at 16 or 12°C. The NI and CL hastened flower bud initiation and flowering, and promoted plant growth as compared with SD at each growing temperature. Plants grown at 16 and 12°C with all NI treatments had the higher numbers of flower buds, leaves, and flowers than those grown at 20°C under SD. Using CL lighting and 16°C could reduce cyclamen production costs during winter by as much as 83% as compared to a natural light and 20°C. Therefore, CL can substitute for continuous NI or heating that enhances the flowering of cyclamen during SD and cold seasons, reducing heating and lighting costs.

Shoot elongation and gibberellin contents in Cyclamen persicum are influenced by temperature and light intensity

Elongated petioles and wide leaf laminas decrease the ornamental quality of potted cyclamen (Cyclamen persicum). We determined the relationship between leaf petiole elongation and lamina expansion and endogenous gibberellins (GAs) of cyclamen as influenced by light intensity, daily light integral (DLI), and temperature. ‘Metis Scarlet Red’ cyclamen plants with five fully unfolded leaves were cultivated in growth chambers maintained at 14°C (low temperature, LT) and 26°C (high temperature, HT) and illuminated at 60 and 240 µmol·m-2·s-1 PPF [(low light (LL) and high light (HL), respectively] with 8 h (short day, SD) and 16 h (long day, LD) photoperiods by fluorescent lamps, giving a total of eight treatments. HT and LL increased petiole length, plant height, and leaf size. There was no significant effect of photoperiod on plant height or petiole length. ‘Metis Scarlet Red’ cyclamen had GA1 and GA4 as active GAs with a similar concentration. The concentration of active GAs was higher in plants grown at the HT compared to the LT. Concentrations of GA20 and GA1, products in the early C-13-hydroxylation pathway, and GA9 and GA4, products of the non C-13-hydroxylation pathway, were higher in plants grown under LL than HL. Petiole length increased linearly by about 6 cm (200%) in all eight treatments as the concentration of active GAs (GA1 + GA4) increased from 12 to 34 ng·g-1. These results indicate that temperature and DLI regulated petiole length of cyclamen by controlling the content of active GAs.

A pilot study: Horticulture-related activities significantly reduce stress levels and salivary cortisol concentration of maladjusted elementary school children

The effects of three horticulture-related activities (HRAs), including floral arranging, planting, and flower pressing were compared to see if they influenced changes on a stress scale and on salivary cortisol concentrations (SCC) in maladjusted elementary school children. Twenty maladjusted elementary school children were randomly assigned either to an experimental or control group. The control group carried out individual favorite indoor activities under the supervision of a teacher. Simultaneously, the ten children in the experimental group participated in a HRA program consisting of flower arrangement (FA), planting (P), and flower pressing (PF) activities, in which the other ten children in the control group did not take part. During nine sessions, the activities were completed as follows: FA-FA-FA, P-P-P, and PF-PF-PF; each session lasted 40 min and took place once a week. For the quantitative analysis of salivary cortisol, saliva was collected from the experimental group one week before the HRAs and immediately after the activities for 9 consecutive weeks at the same time each session. In the experimental group, stress scores of interpersonal relationship, school life, personal problems, and home life decreased after the HRAs by 1.3, 1.8, 4.2, and 1.3 points, respectively. In particular, the stress score of school life was significantly reduced (P < 0.01). In addition, from the investigation of the SCCs for the children before and after repeating HRAs three times, it was found that flower arrangement, planting, and flower pressing activities reduced the SCCs by ≥37% compared to the SCCs prior to taking part in the HRAs. These results indicate that HRAs are associated with a reduction in the stress levels of maladjusted elementary school children.