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- Author or Editor: Margaret McMahon x
- Journal of the American Society for Horticultural Science x
Two chrysanthemum [Dendranthema ×grandiflorum (Ramat) Kitamura] cultivars, `Spears' and `Bright Golden Anne', were grown under artificial short or natural long photoperiod in benchtop chambers covered with clear double-walled acrylic panels (control) or under similar panels filled with CuSO4 (CuSO4 *5H2O in solution at 6% w:v) that removed far-red (FR) (700 to 800 nm) light. Three times per week, a tip from one lateral branch from each of three plants per chamber was harvested and the stage of meristem development recorded. The experiment was conducted April through May and repeated May through June. For `Spears' all short photoperiod treatments developed floral primordia at the same time and the rate of development did not differ. All plants in natural photoperiod treatments initiated flower primordia simultaneously with plants in short photoperiod treatments, but development was delayed ≈3 d in the first experiment compared to plants receiving short photoperiods. During the longer photoperiods of the second experiment, plants under FR-absorbing filters and receiving natural photoperiods initiated and developed flowers ≈2 d after plants in short photoperiod treatments initiation and development. Plants under control filters and natural photoperiods had initiation delayed by ≈4 d and development was delayed by ≈11 d. Bud development was normal for all treatments. For `Bright Golden Anne' only short photoperiod treatments developed normal floral primordia. Plants under FR-absorbing filters and exposed to natural photoperiods eventually initiated floral primordia but development was abnormal. No floral primordia developed under natural photoperiod and control filter conditions. The results indicate that if FR-absorbing filters are used to regulate height of chrysanthemum and possibly other photoperiodic plants, the time of flowering may be affected. However, if artificial short photoperiods are imposed with the use of blackout cloth, FR-absorbing filters do not affect flowering response.
`Celebrity White' hybrid petunia plants (Petunia ×hybrida Hort. Vilm-Andr.) were grown either in chambers constructed of CuSO4-filled panels acting as spectral filters removing the far-red light (-FR) or in environmental control chambers under temperature treatments of 24 °C day/18 °C night (+DIF) or 18 °C day/24 °C night (-DIF). Growth responses for plants grown under CuSO4 filter (-FR) or -DIF temperatures were similar in that both treatments resulted in decreased internode length, increased stem diameter, and decreased cell length and cell diameter in epidermal, cortical, and pith tissues. Reduced cortical cell length contributed the largest percentage to internode length reductions compared to epidermal and pith tissue for the -FR treatment while reductions in cell length of all three tissues contributed to internode reduction of -DIF-treated plants. Chlorophyll a increased for plants grown under -FR, but decreased for plants grown in -DIF when compared to the appropriate controls.
Leaves of chilled `Moss-Agate' Episcia (Mart.) plants exhibited direct chilling injury (i.e., watersoaked browning of leaf blade interveinal areas within 24 h of exposure to low temperature) immediately following exposure in darkness to 10C for 0.5 or 1.0 h. Chlorophyll fluorescence peak: initial ratios and terminal: peak ratios of chilled Episcia were -reduced 20% and 25%, respectively, 3 h after chilling, a result suggesting possible photosystem II damage. Total leaf chlorophyll content was reduced by 17% within 3 h of chilling and CO2uptake also was reduced at this time. Leaves of chilled `Rudolph Roehrs' Dieffenbachia maculata (Lodd.) (D. Roehrsii Hort.) plants expressed no visible injury within 24 h of 1.2C chilling in darkness for 36,48, or 60 h, but CO2uptake was reduced by 70% compared to the control 3 h after chilling. Visible injury began to appear 27 h after chilling, and the older leaf blades of all chilled plants exhibited a watersoaked appearance 75 h after chilling. Chlorophyll fluorescence peak: initial ratios of chilled Dieffenbachia did not vary, and terminal: peak ratios were not reduced until 147 h after chilling, when the injured tissue was extremely flaccid and translucent. Chilling reduced the chlorophyll content of Dieffenbachia by 10% in some plants 27 h after chilling and by 35%. in all plants 75 h after chilling. Transpiration rate was reduced and stomata] diffusive resistance increased 27 h after chilling.