Search Results

You are looking at 1 - 10 of 693 items for :

  • dark���light cycles x
  • Refine by Access: User-accessible Content x
Clear All
Full access

Nguyen Phuc Huy, Vu Quoc Luan, Le Kim Cuong, Nguyen Ba Nam, Hoang Thanh Tung, Vu Thi Hien, Dung Tien Le, Kee Yoeup Paek, and Duong Tan Nhut

-elongated ex vitro explants as the source under dark–light cycles for plant regeneration through internode tissue cultures. The results of this study provide a new approach to micropropagation of P. callosum for commercial propagation. Materials and Methods

Free access

Zejin Zhang, Dongxian He, Genhua Niu, and Rongfu Gao

a 12-h photoperiod (24-h light–dark cycle). CO 2 concentration was controlled at 500 ± 50 μmol·mol −1 and PPF at canopy level was maintained at 160 μmol·m −2 ·s −1 , provided by fluorescent lamps. Effects of drought and rewatering on net CO 2

Free access

Desmond G. Mortley, Douglas R. Hileman, Conrad K. Bonsi, Walter A. Hill, and Carlton E. Morris

PPF for 18 h daily, and the temperature lowered from 28/22 °C light/dark to a constant 20 °C. Plants remained under these conditions for 14 d, after which the original PPF and temperature cycles were restored. Nutrient solution. A modified half

Free access

Eduardo J. Chica and L. Gene Albrigo

collected at 0800 and 1500 hr . Data were analyzed using a repeated measurements model with four tree replicates. ANOVA was used to compare CsFT transcript abundance before and after the cold front. Influence of light/dark cycles on transcript abundance

Full access

Toshio Shibuya, Junki Komuro, Norio Hirai, Yoshiko Sakamoto, Ryosuke Endo, and Yoshiaki Kitaya

in a growth chamber maintained at 28 °C and a relative humidity of 50% at a photosynthetic photon flux ( PPF ) of 300 μmol·m −2 ·s −1 provided by FLs (FHF32EX-N-H; Panasonic, Kadoma, Japan) in a 12/12-h light/dark cycle. After the cotyledons had

Full access

Susan M. Hawkins and Carol D. Robacker

little bluestem by culturing mature caryopses under dark conditions, so that light was excluded from the cultures, on Linsmaier and Skoog (LS) medium with kinetin and 2,4-D ( Li et al., 2009 ). Shoots were regenerated by transferring the calli to medium

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

N.C. Yorio, G.W. Stutte, G.D. Goins, D.S. de Villiers, and R.M. Wheeler

The effects of planting density and short-term changes in photoperiod on the growth and photosynthesis of bean (Phaseolus vulgaris L.) was investigated. Two cultivars of bean (cv. Etna, a dry bean variety; cv. Hystyle, a snap bean variety) were grown using nutrient film technique hydroponics in a walk-in growth chamber with a 12 h/12 h (light/dark) photoperiod and a corresponding thermoperiod of 28/24 °C (light/dark) and constant 65% relative humidity. Lighting for the chamber consisted of VHO fluorescent lamps and irradiance at canopy level was 400 μmol·m-2·s-1 PPF. For each cultivar, plants were grown at densities of 16 or 32 plants/m2. Short-term photoperiod changes were imposed during vegetative growth (21-29 DAP) and pod-fill (42-57 DAP). From the base 12 h/12h (light/dark) photoperiod, lighting in the chamber was cycled to provide 18 h/06 h (light/dark) or 24 h/0 h(continuous light) for 48 h. Diurnal single leaf net photosynthetic rates (Pn) and net assimilation vs. internal CO2 (Aci) measurements were taken during the short-term photoperiod adjustments. Results showed that there was no difference between cultivars or planting density with regard to total biomass or single leaf photosynthetic rates, but cv. Etna produced 35% more edible biomass than cv. Hystyle. Additionally, there was no effect of short-term photoperiod adjustment on single leaf Pn or Aci.