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  • Author or Editor: Michael S. Reid x
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Abstract

Abscission (Latin: ab-from, scindere- to cut or sunder), is the process by which plants shed lateral organs. The fundamental event in all abscission is the secretion of enzymes which hydrolyze the cellulose “exoskeleton” and the pectin “cement” of the cells in the abscission zone. This hydrolysis often is accompanied by ingenious mechanisms to assist removal of the abscising organ. The early appearance of these processes in the fossil record (6) is evidence of the strong evolutionary advantage to plants of shedding organs, whether it be the removal of leaves to avoid snow load or drought stress, or the shedding of fruit or seeds to ensure their dispersal and continuation of the species.

Open Access

The respiration of flowers of stock [Matthiola incana (L.) R. Br.] had a Q10 of 6.9 between 0 and 10 °C. Simulated transport for 5 days resulted in marked reduction in the vase life of flowers transported at 10 °C and above. Flower opening, water uptake, and vase life of the flowers increased somewhat in a vase solution containing 50 ppm NaOCl, and considerably in a commercial preservative containing glucose and a bactericide. Exposure to exogenous ethylene resulted in rapid desiccation and abscission of the petals, effects that were prevented by pretreatment with 1-methylcyclopropene (1-MCP). Even in the absence of exogenous ethylene, the life of the flowers was significantly increased by inhibiting ethylene action using pretreatment with silver thiosulfate (STS) or 1-MCP. STS was more effective than 1-MCP in maintaining flower quality.

Free access

The respiration of cut flowers of gerbera (Gerbera jamesonii H. Bolus ex Hook.f. `Vesuvio') and sunflower (Helianthus annuus L.) increased exponentially with increasing storage temperature. Poststorage vase life and negatively gravitropic bending of the neck of the flowers were both strongly affected by simulated transport at higher temperatures. Vase life and stem bending after dry storage showed highly significant linear relationships (negative and positive, respectively) with the rate of respiration during storage. The data indicate the importance of maintaining temperatures close to the freezing point during commercial handling and transport of these important commercial cut-flower crops for maximum vase life.

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Research that led to the discovery of 1-methylcyclopropene (1-MCP) started with efforts to understand the effects of controlled atmosphere storage and continued with studies that examined the nature of the ethylene binding site. Although some researchers focused on the use of silver ion for inhibiting ethylene action, Sisler and his colleagues focused on analogs of olefins that had a similar effect. Efforts to tag the binding site using activation tagging with diazocyclopentadiene led to the discovery of the dramatic effects of cyclopropenes, which were identified as products of its photooxidation. The story is a testament to the value of fundamental research and the collegiality and unique intellectual and technical abilities of the primary inventor, Edward C. Sisler.

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The first commercial use of 1-methylcyclopropene (1-MCP) was with cut flowers and potted plants, and treatment with this compound is still the preferred strategy for protection of most ethylene-sensitive crops. Research is continuing into optimum treatment conditions and strategies for efficient application in commerce. In studies using carnation (Dianthus caryophyllus L. ‘White Sim’) petals to determine the optimal conditions for commercial treatment, we noted some aspects of the inhibition response that were not consistent with the current competitive inhibition model of 1-MCP action. Our data are better explained by an alternative model in which 1-MCP binds to a site that is exposed during the allosteric changes that accompany the enzymatic activities of the binding site in the absence of ethylene.

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Spraying flowering plants of Schlumbergera truncata (Haw.) `White Christmas' with aminoethoxyvinylglycine (AVG), an inhibitor of ethylene biosynthesis, did not prevent the rapid loss of flower buds caused by exposure to 1 μl of ethylene/liter. Treatment with the silver thiosulfate anionic complex (STS) strongly inhibited such effects. The rate of bud drop in ethylene-free air (interior environment room) was somewhat reduced by AVG treatment, although total display life of treated plants was not significantly different from that of the controls. STS treatment reduced the rate of bud drop, and increased display life by 20 %.

Free access

Regardless of their maturity at harvest, the vase life of cut inflorescences of the hybrid Limonium `Fantasia' placed in deionized water was 4 to 5 days. A vase solution containing Physan (a quaternary ammonium disinfectant solution) at 200 μl·liter–1 and 20 g sucrose/liter not only prolonged the longevity of individual florets but also promoted bud opening so that the vase life of cut inflorescences extended to 17 days. Pulse treatment with 100 g sucrose/liter in combination with Physan at 200 μl·liter–1 for 12 hours partially substituted for a continuous supply of sucrose. Including 30 mg gibberellic acid/liter in the vase solution was without benefit.

Free access

After storage at different temperatures for a simulated transportation period, the vase lives at 20 °C (68 °F) of carnations (Dianthus caryophyllus `Imperial White'), daffodils (Narcissus pseudonarcissus `King Alfred'), iris (Iris hollandica `Telstar'), killian daisies (Chrysanthemum maximum), paperwhite narcissus (Narcissus tazetta `Paperwhite'), roses (Rosa {XtimesX} hybrida `Ambiance'), and tulips (Tulipa gesneriana) decreased with increasing storage temperature. There were no significant differences between the vase life of flowers stored dry and flowers stored in water when storage temperatures were from 0 to 10 °C (32 to 50 °F). The vase life after wet storage at temperatures of 12.5 °C (54.5 °F) and greater was significantly higher than vase life after dry storage at those temperatures for all the flowers studied. Iris and carnation flowers survived storage at 15 and 20 °C (59 and 68 °F) only when stored in water.

Full access

Abstract

Rhythmic pulses of irreversible petal expansion in rose (Rosa hybrida L. ‘Sonia’) petals cause diurnal changes in the rate of flower opening. Time-lapse cinematography revealed a transient increase in the rate of rose flower opening that commenced shortly before the onset of a light period and lasted for a few hours. Petal expansion, which occurred sequentially from the outer to the innermost whorl, involved rhythmic increases in fresh and dry weights. The amount of expansion was greatest in the distal portion of each petal and least near the petal base. Periods of rapid expansion were accompanied by decreases in starch and increases in soluble sugars in the petals, but the total carbohydrate content of the petals remained constant during a light–dark cycle. During expansion, the osmotic potential of the outer petal increased from −790 to −690 kPa. Starch hydrolysis during petal growth appears to be important for maintenance of cell size, but it is not the factor controlling cell expansion.

Open Access

Abstract

After 4 days, zygocactus plants (Schlumbergera truncata) exposed to air containing 0.5, 5 and 50 µl/liter C2H4 or held in the dark at 26°C dropped all their buds and flowers. Foliar application of silver thiosulfate (STS) significantly reduced flower and bud abscission of zygocactus plants stressed by exposure to C2H4 or 26°C plus dark even 4 weeks after application. Phytotoxicity was negligible when the silver concentration was 2 mm or less.

Open Access