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- Author or Editor: William W. Miller x
Easter liliy (Lilium longiflorum Thunb. `Nellie White') bulbs were stored in moist peatmoss for up to 85 days at – 1.0 or 4.5C. Bulbs were periodically removed from storage and analyzed to determine levels of soluble carbohydrates and starch. Storage at – 1.0C induced large accumulations of sucrose, mannose, fructose, and oligosaccharide in both mother and daughter scales. Starch concentration declined substantially during this period. Storage at 4.5C resulted in less dramatic alterations in bulb carbohydrates, although trends toward increased soluble carbohydrates and reduced starch levels were seen. The accumulation of mannose suggests that glucomannan, a secondary storage carbohydrate, was also degraded during – 1.0C storage.
Abstract
The feasibility of utilizing different patterns of air temperature changes over the light and dark periods was investigated to provide a basis for greenhouse energy conservation. ‘Grand Rapids’ lettuce was grown hydroponically in microprocessor controlled growth chambers, under a light level of 325 µmol s-1m-2 PPF. Air temperatures were: a) increased from 15° to 35°C (late-peak), b) decreased from 35° to 15° (early-peak), and c) increased to 35°, then back to 25° (mid-peak) during the 16-hr light period. The late and mid-peak patterns had a gradual decrease in night air temperature, whereas the early peak pattern had a gradual increase in night air temperature. Each of these patterns averaged 25° during the light period, and 20° during the dark period. “Early-peak” plants grew poorly, whereas plants grown under the mid- and late-peak regimes grew well. Early morning diffusive resistance was similar for early- and mid-peak plants. Transpiration rates followed the air temperature changes.
Abstract
The effects of reduced irradiance on dry weight partitioning in Easter lilies was examined by forcing vernalized bulbs of Lilium longiflorum Thumb. ‘Nellie White’ during two growing seasons. Forcing commenced in a glasshouse under standard growing conditions; immediately following flower bud initiation (FBI), plants were transferred to a range of irradiance reduction treatments (0%, 20%, 50%, or 85% reduction) in the greenhouse or to complete darkness in a growth chamber. Greenhouse irradiance reduction treatments resulted in alterations in whole-plant source-sink relationships. Total plant dry weight and overall plant quality were reduced in shaded plants. The depletion rate of mother bulb dry matter was not affected by reduced irradiance, whereas daughter bulb reserve loss was increased by irradiance reduction treatments. There was no daughter bulb reserve remobilization in plants grown in complete darkness after FBI. Flower bud and open flower dry weights were progressively reduced as irradiance was reduced. With an 85% irradiance reduction, plants forced from 17.5-cm bulbs had 63% bud abortion, whereas, with 20.0-cm bulbs, only 12% of the buds aborted. Plants grown in complete darkness after FBI became etiolated, and flowers failed to open. These results demonstrate differences in the ability of various morphological regions of the bulb to respond to reductions in greenhouse irradiance. Since the daughter bulb response to reduced irradiance was relatively slow, additional remobilization of dry matter from the daughter bulb is probably of minimal benefit during short periods of reduced irradiance in commercial greenhouses.
Abstract
Changes in carbohydrate types and quantities in the bulbs, stems, leaves, and buds of Easter lilies (Lilium longiflorum Thunb. ‘Nellie White’) forced under ambient or reduced irradiance conditions were investigated. Analysis by high-performance liquid chromatography (HPLC) revealed that sucrose is the dominant soluble carbohydrate in bulb tissues, with glucose, fructose, and mannose present at significantly lower concentrations. During growth of the flowering shoot, mother bulb reserves are preferentially used regardless of greenhouse irradiance. Beginning 40 days after planting, there was a steady decrease in mother bulb starch concentration until anthesis, 70 days later. Increased bulb sucrose, glucose, mannose, and fructose concentrations were correlated with the induction of starch breakdown and carbohydrate export. Under natural greenhouse irradiance conditions, daughter bulb carbohydrate reserves were not used, as starch and soluble carbohydrate concentrations remained constant. Irradiance reductions of 50% to 85% significantly reduced total carbohydrate concentration in leaves and floral buds and induced export from the daughter bulb, as evidenced by elevated levels of daughter bulb soluble carbohydrates and reductions in starch concentration. Dark-grown plants exhibited similar daughter bulb carbohydrate metabolism patterns as plants grown in full sun: starch was not hydrolyzed and soluble carbohydrates did not increase in concentration. Collectively, these results suggest 1) bulb export metabolism is characterized by elevated soluble carbohydrate concentrations, 2) there is a minimum irradiance requirement for carbohydrate export processes from the daughter bulb, and 3) reductions in greenhouse irradiance result in reduced carbohydrate levels in Easter lily leaves and flower buds.
Ethephon [(2-chloroethyl) phosphonic acid] is a plant growth regulator (PGR) that releases ethylene following application. Although ethephon is commonly used as a foliar spray during the commercial production of ornamental crops, including spring bulb crops such as daffodil (Narcissus pseudonarcissus L.), there has been increased interest in using ethephon as a root-zone-applied PGR. In this work, we evaluated a number of factors important for the development of ethephon as a soil drench for daffodil. Results indicate that a given dose (milligrams ethephon per pot) could be applied in volumes ranging from 15 to 120 mL (per 15-cm pot) with equal efficacy. Similarly, the same dose of ethephon could be applied as a foliar/substrate surface spray with volume of 105 to 525 mL·m−2 with equal efficacy. Although the efficacy of ethephon drenches interacted with forcing temperature, drenches were nonetheless effective across the range of temperatures commonly used for daffodil production. Plant size at the time of ethephon application had no effect on final plant size (at flower senescence). The rate of ethylene release from a peat-based substrate was highly temperature dependent, and ethephon was readily leached from this same substrate.
Low-temperature storage potential of rooted cuttings of garden chrysanthemum [Dendranthema ×grandiflorum (Ramat.) Kitamura] cultivars and its relationship with carbohydrate reserves were evaluated. Storage of chrysanthemum cuttings at -1 and -3 °C resulted in freezing damage. Visual quality of rooted cuttings stored at 0 or 3 °C varied among cultivars. Quality of `Emily' and `Naomi' cuttings was reduced within a week by dark storage at 0 or 3 °C due to leaf necrosis, while `Anna' and `Debonair' cuttings could be held for 4 to 6 weeks without significant quality loss. In `Anna' and `Debonair', low-temperature storage reduced the number of days from planting to anthesis regardless of storage duration. However, flowers of plants grown from stored cuttings were smaller than those of nonstored cuttings. At the beginning of storage, `Emily' and `Naomi' had lower sucrose, glucose, and fructose (soluble sugars) content compared to `Anna' and `Debonair'. Regardless of temperature, leaf soluble sugar was significantly reduced by dark storage for 4 weeks. In stems, sucrose and glucose were reduced while fructose generally increased during low-temperature storage probably due to the breakdown of fructans. Depletion of soluble sugars and a fructan-containing substance during low-temperature dark storage was greater in `Emily' and `Naomi' than in `Anna' and `Debonair'. Low irradiance [about 10 μmol·m-2·s-1 photosynthetically active radiation (PAR) from cool-white fluorescent lamps] in storage greatly improved overall quality and delayed the development of leaf necrosis in `Naomi'. Cuttings stored under light were darker green and had a higher chlorophyll content. Leaf and stem dry weights increased in plants stored under medium and high (25 to 35 μmol·m-2·s-1 PAR) irradiance while no change in dry weight was observed under dark or low light. Results suggest that the low-temperature storage potential of chrysanthemum cultivars varies considerably, and provision of light is beneficial in delaying the development of leaf necrosis and maintaining quality of cultivars with short storage life at low temperatures.
Soluble carbohydrate extracts from Antirrhinum majus L. leaves were fractionated by ion exchange chromatography. Putative mannitol was tentatively identified by retention behavior on two high performance liquid chromatography columns. Mannitol was confirmed using 1H and 13C nuclear magnetic resonance (NMR), and by gas chromatography (GC) and mass spectroscopy (MS). The melting point of authentic and putative mannitol, and a 1:1 mix was from 164 to 166°C. Using the EDTA-phloem exudate technique, mannitol was detected in phloem tissue associated with mature flowers, flower buds, and mature leaves, suggesting that mannitol is translocated in Antirrhinum.
Abstract
Root-knot nematode (Meloidogyne hapla) juvenile population increased and carrot (Daucus carota L.) yield progressively decreased during eight continuous carrot crops grown over 37 months. When ‘Haifa’ and common white clovers (Trifolium repens L.) were cropped for 29 months and plowed down, two succeeding carrot crops suffered severe yield and quality losses and the juvenile nematode population in the soil in-creased greatly. However, there were significantly fewer juveniles in the soil and significantly higher yield and better quality of carrots when nematode-resistant ‘Nevada Synthetic XX’ and ‘Nevada Synthetic YY alfalfas (Medicago sativa L.) and continuous cultivation preceeded the carrots.