Redbud (Cercis canadensis) is a small woody ornamental legume that has a hard seed coat, which imposes physical dormancy, typical of many legumes. Redbud also possesses an internal embryo dormancy that must be overcome by stratification. In order to observe the relationship between anatomy and germination, seeds were embedded in JB-4 resin during various developmental and germination stages. The seeds were cut longitudinally with a glass bladed microtome, to observe the radicle, vascular traces and testa. It appears that the vascular traces left from the funiculus serve as a weak point in non-dormant seeds that allows the radicle to rupture the testa during germination.
Forest products companies would like to grow clonal plantations of superior loblolly pine (Pinus taeda L.) to improve fiber yields. Feasibility depends on developing efficient propagation techniques and finding superior clones. Horticultural stem-cutting propagation methods and micropropagation techniques are being coupled to test, preserve, multiply, and ultimately deploy clones. Outstanding clones are being found through a series of field tests; each beginning with a superior full-sibling cross from a 40-year-old breeding program. Clones are first screened for rooting ability, and the top 25% to 35% of clones are then established on four sites. Since maintenance of juvenile phase tissue is critical to perpetuating high rooting rates and fast subsequent growth, each clone is preserved as a set of serially propagated hedges and as cold-stored microshoots. As field tests age, better-performing clones are multiplied gradually. Large-production stock blocks of juvenile hedges consequently may be established from both rooted cuttings and microshoots as soon as field tests end. Clones producing large numbers of long branches have been noted for their potential value as fast-growing ornamentals. Since such characters are opposite those desirable for forestry, these clones would need to be preserved, multiplied, and marketed separately from clones for plantation forests.
Seed coat anatomy in the hilar region was examined in dry, imbibed and germinating seeds of Eastern redbud. A discontinuous area was observed between macrosclereid cells in the palisade layer of the seed coat which formed a hilar slit. A symmetrical cap was formed during germination as the seed coat separated along the hilar slit and was hinged by the macrosclereids in the area of the seed coat opposite to the hilar slit. The discontinuity observed in the palisade layer was the remnant of the area traversed by the vascular trace between the funiculus and the seed coat of the developing ovule. There were no apparent anatomical differences in the hilar region of the seed coat between dormant and non-dormant imbibed seeds. However, the thickened layer of mesophyll cells of the seed coat in this region and the capacity of the endospetm to stretch along with the elongating radicle may contribute to maintaining dormancy in redbud seeds.
The seedcoat anatomy in the hilar region was examined in dry, imbibed and germinating seeds of Eastern redbud (Cercis canadensis L.). A discontinuous area was observed between macrosclereid cells in the palisade layer of the seedcoat which formed a hilar slit. A cap was formed during germination as the seedcoat separated along the hilar slit and was hinged by the macrosclereids in the area of the seedcoat opposite to the hilar slit. The discontinuity observed in the palisade layer was the remnant of the area traversed by the vascular trace between the funiculus and the seedcoat of the developing ovule. There were no apparent anatomical differences in the hilar region of the seedcoat between dormant and nondormant imbibed seeds. However, the thickened mesophyll of the seedcoat in this region and the capacity of the endosperm to stretch along with the elongating radicle may contribute to maintaining dormancy in redbud seeds.
Postharvest treatments designed to enhance the vase life of cut Gloriosa rothschildiana flowers were tested. Vase life was significantly extended by the germicides 8-HQC (250 mg·liter-1), DICA (50 mg·liter-1), and Physan-20 (50 mg·liter-1). Germicides acted primarily by improving solution uptake. Sucrose, either as a continuous treatment (of 2% or 5% w/v), or as a 24-hour pulse (20%), significantly enhanced vase life, primarily by enhancing the development of immature buds and delaying senescence in open flowers. Flowers stored at 1C developed signs of chilling injury within 3 days, but chilling symptoms were not displayed in stems stored at 10C for 10 days. Flowers were not affected when exposed to 50 μl ethylene/liter for 24 hours. Transport and short-term storage in sealed, air-filled bags to protect the flowers from physical damage resulted in some atmosphere modification within the bags. Fungal growth occurred when flowers were kept in air-tilled bags for more than 6 days, resulting in a reduction in vase life. Chemical names used: 8-hydroxyquinoline citrate (8-HQC); sodium dichloroisocyanuric acid (DICA); n-alkyl dimethyl ethylbenzyl ammonium chloride (Phyrsan-20).
The effect of DICA (50 mg·liter-1), BCDMH (12 mg available chlorine/liter), and HQC (250 mg-liter]) on the longevity of 14 popular cut flower species was assessed. Longevity was significantly extended in: Rosa hybrida L. `Gabrielle' and Scilla campanulata L. Squill. by all germicides; Lilium parkmannii L. `Nepal', Gerbera jamesonii L. `Mercy', and Narcissus tazetta L. `Fortune' by DICA and BCDMH; Gypsophila paniculata L. `R22' by DICA and HQC; and Freesia hybrida Eckl. ex Klatt `White Bergunden' by BCDMH. No effect on longevity was found in Dendranthema grandiflora (Ramat) Kitamura. `Horim', Dianthus caryophyllus L. `Medea', Dianthus barbatus L., Iris hollandica L. `Pearl', and Gerbera jamesonii L. `Double Delight'. Longevity was significantly reduced by DICA in Alstroemeria aurantiaca L. `Mona Lisa' and Tulipa hybrida L. `Apeldoorn'. Analysis of microbial concentrations showed that proliferation was effectively controlled by DICA and BCDMH, but not by HQC. Levels of up to 106 cfu·ml-1 were detected in water, indicating that species not affected by germicides can tolerate these microbial quantities. Fresh weight and solution uptake data indicated that germicides acted primarily by improving solution uptake. Longevity was significantly reduced in R. hybrida `Gabrielle' and D. caryophyllus `Medea' flowers placed in solutions containing high counts of microorganisms (>108 cfu·ml-1) isolated from D. caryophyllus or R. hybrida. Chemical names used: 1-bromo-3-chloro-5,5-dimethylhydantoin (BCDMH); sodium dichloroisocyanuric acid (DICA); 8-hydroxyquinoline citrate (HQC).
The vase life of cut sunflowers given a simulated transport period (3 days dry storage at 8C) was significantly enhanced by a l-hour pulse with 0.01% Triton X-100 administered before storage. The Triton pulse increased solution uptake during the l-hour pulse, decreased fresh weight loss during dry storage, and significantly improved water uptake thereafter, resulting in greater leaf turgidity and longer vase life. Leaf stomata] conductance measurements indicated that Triton X-100 maintained stomatal opening at a higher level during the pulse and after storage, but had no effect during dry storage. Chemical name used: octylphenoxypolyethoxyethanol (Triton X-100).
The opening and senescence of gladiolus (Gladiolus sp.) florets was accompanied by climacteric or nonclimacteric patterns of respiration and ethylene production, depending on variety, and whether data were expressed on a fresh-weight or floret basis. A climacteric pattern of ethylene production by the youngest buds on the spike (which never opened) was stimulated by cool storage, and was not affected by holding the spikes in a preservative solution containing sucrose. Ethylene treatment had no effect on senescence of the florets of any of the cultivars tested. Pulse treatment of the spikes with silver thiosulfate (STS) improved floret opening but not the life of individual florets. Sucrose and STS had similar but not synergistic effects on floret opening, suggesting that STS improves flower opening in gladiolus by overcoming the effects of carbohydrate depletion.
Phosphine (PH3) is a potential alternative fumigant to methyl bromide for insect disinfestation of cut flowers. King protea (Protea cynaroides L.), tulip (Tulipa gesneriana `Apeldoorn'), kangaroo paw (Anigozanthos manglesii Hook.), and geraldton wax (Chamelaucium uncinatum `Purple Pride') were fumigated with PH3 at varying concentrations (100 to 8000 μL·L-1) for 2, 4, or 6 hours. Vase life was evaluated at 20 °C, 65% relative humidity, and constant illumination with a photosynthetically active radiation of 15 μmol·m-2·S-1. No significant change in vase life was observed for kangaroo paws after any of the PH3 fumigations. A 6-hour fumigation at 8000 μL·L-1 significantly reduced vase life in king protea, tulip, and geraldton wax flower. Geraldton wax flower and tulip were relatively sensitive to PH3, as they were damaged by 4000 μL·L-1 for 6 hours and 8000 μL·L-1 for 4 hours, respectively. Phosphine has potential as an insect disinfestation fumigant for king protea, tulip, and kangaroo paw at 4000 (μL·L-1 for 6 hours without affecting vase life or causing damage.
Petal opening and senescence of cut Gladiolus, Iris, and Narcissus flowers was significantly inhibited by continuous treatment with 1 mm CHI. Vase life was doubled in individual flowers treated when half-open, and a similar effect was detected after pulsing cut gladiolus spikes with 1 mm CHI for 24 hours. Petal wilting was markedly inhibited in flowers treated with CHI and was confined to the outer 2 to 3 mm of petal margins as opposed to the entire petal in untreated flowers. These effects were not seen, however, in CHI-treated cut tulip flowers, where vase life was significantly reduced. CHI markedly inhibited protein synthesis in Gladiolus `New Rose' florets (a decrease of >60%). Treatment with a potent biocide, DICA, did not increase vase life; therefore, CHI was not prolonging flower longevity by preventing microbial growth in the vase solution. The results indicate that de novo protein synthesis is required for bulb flower development and opening and petal wilting and senescence. Chemical names used: cycloheximide (CHI), sodium dichloroisocyanuric acid (DICA).