An experiment was initiated to evaluate the effects of previously recommended seed treatments for baldcypress [Taxodium distichum (L.) Rich.] or pondcypress [Taxodium distichum (L.) Rich. var. imbricarium (Nutt.) Croom] on Montezuma cypress [Taxodium distichum (L.) Rich. var. mexicanum Gordon], and to determine which, if any, provided optimum germination. Factorial combinations of seed treatments and stratification (2 °C for 0, 45, or 90 d) were applied to seeds of Montezuma cypress. Treatments included: 1) 90% ethanol 5 min soak, 2) ethyl ether 5 min soak, 3) 100 mg·L-1 citric acid 48 h soak, 4) mechanical scarification, 5) five hot water baths (42 °C) allowing the water to cool to room temperature between baths, and 6) a non-treated control. Three more seed treatments consisted of water soaks at room temperature (25 °C) for 0, 45, or 90 d. Seeds were germinated on moist filter paper in a growth chamber with a 12-h day/night photoperiod at a constant 25 °C. Data was collected daily for 14 d and then weekly for the following 4 wks. Radicle elongation of 1 cm was considered germination. Without stratification, 100 mg·L-1 citric acid and the hot water bath treatments were significantly different from other treatments by 7 d, though not from each other, with a mean cumulative germination of 15.6% and 12.2%, respectively. By 14 d, the 100 mg·L-1 citric acid treatment differed only from the ethyl ether wash attaining 28.9% and 14.4% germination, respectively. There were no other statistically significant differences observed among any other treatments without stratification. Germination percentages were low,<30%, without stratification. Effects of additional stratification will also be discussed.
Geoffrey C. Denny* and Michael A. Arnold
This study was undertaken to find the most suitable treatment to promote germination in seeds from hardy shrub roses used in a breeding program.
Leslie L. Dean
Persistent-green color has been incorporated into curly top and common beanmosaic virus resistant snap beans. Cooperative observation and processing trials throughout the United States indicate wide adaptability and good commercial potential for several lines. Release, during 1968, of one or more of these snap beans, to commercial seedsmen for seed increase is anticipated.
N. Y. Liu, H. Khatamian, and T. A. Fretz
Seed germination was 90–95% for Kentucky coffeetree [Gymnocladus dioicus (L.) C. Koch] after concentrated sulfuric acid treatment for 120 to 150 minutes; 97–98% for honeylocust (Gleditsia triacanthos va. inermis L.) following 60, 90, or 120 minutes concentrated sulfuric acid scarification; and was 67–72% for redbud (Cercis canadensis L.) after 30, 60, or 90 minutes of concentrated sulfuric acid scarification followed by a 60-day stratification period. Scanning electron micrographs of acid-scarified Kentucky coffeetree, honeylocust, and redbud seed indicated that lumens of the macrosclereid cells on the seed surface were exposed after acid treatment, permitting imbibition of water. Boiling water treatment ruptured the macrosclerid layer, while seed treated with liquid N2 had fissures that did not appear to penetrate the macrosclereid layer.
Rebecca C.-C. Hsu and Yung-I Lee
The histological and histochemical changes in developing seeds of Cypripedium debile Rchb. f., a native slipper orchid species with horticultural potential, were investigated. The effects of timing for seed collection, culture media, and cultural conditions were also examined. The optimum germination percentage occurred when mature seeds were collected and sowed on 1/4 Murashige and Skoog basal medium. Besides, the liquid culture promoted germination of mature seeds. This finding is contrary to most other Cypripedium species, which are relatively easy to germinate with immature seeds. Moreover, two notable cytological changes of C. debile were observed. First, the suspensor cell protruded beyond the micropyle opening of the inner seedcoat, making the inner seedcoat not substantial. Second, Nile red staining indicated that the deposition of cuticular material on the seedcoat was fragmentary. It is proposed that the less hydrophobic nature of the seedcoat makes mature seeds of C. debile easier to obtain water and nutrients for germination.
R. Holubowicz, A.G. Taylor, M.C. Goffinet, and M.H. Dickson
During imbibition, water always follows the same pattern when entering the seed testa in semihard seeds (SHS) of snap bean (Phaseolus vulgaris L.). Water first enters the raphe and the chalazal region of the testa (R-CT), then migrates circumferentially along the midline of the seed, leaving the lateral faces the last to be fully imbibed. The R-CT region is the main site of primary uptake of both water vapor and liquid water by SHS. The hilum, micropyle, and strophiole play only a minor role in water uptake in SHS. In comparison to the readily permeable seeds of ‘Bush Blue Lake 47’, SHS have more total phenols in the osteosclereid cells and more pectic substances in the palisade cells of the CT. The presence of these compounds may account for the impermeable nature of SHS. Measurements made of palisade cell length and width in the R-CT region revealed that cell length increased and width decreased in the chalazal testa region (CT) as seed moisture content increased from 6% to 12%. It is proposed that semihardening of bean seeds is mainly a result of the reversible physical changes in the length and width of the palisade cells in the R-CT region. Seeds imbibe at high moisture content (12%) because the palisade cells have stretched, which allows water uptake. Seeds are impermeable at low moisture content (6%) because the palisade cells change in size and form a physical barrier to water movement.
H. J. Toit du, G. Jacobs, and D. K. Strydom
Cold requirement for germination of excised ‘Kakamas’ peach (Prunus persica (L.) Batsch) embryos was satisfied after 2 weeks at 4.4°C; embryos with testas intact required 4 weeks, while seeds with intact endocarps required 12 weeks stratification. Leaching of unstratified excised embryos stimulated germination. The endocarp affected germination by delaying water uptake. Supplying additional O2 during stratification or germination of seeds with intact endocarps did not improve germination. Cracking the endocarps stimulated germination of stratified seeds, but sealing the cracks with lanolin paste prevented this effect. The endocarps may interfere with the leaching of inhibitors from the testa and embryo. Initial seedling growth of embryos with or without testas increased linearly with increasing time of stratification in terms of shoot length, dry weight of shoots and leaves, dry weight of roots and leaf area, length and width. Seedlings arising from embryos with intact testas were taller and had a greater dry mass of shoots, leaves and roots compared to seedlings arising from embryos without testas.
T. A. Campbell
Stokes aster [Stokesia laevis Hill (Greene)] is a perennial ornamental; achenes are a prospective source of vernolic acid for the chemical industry. Responses of achenes of 6 Stokes aster accessions to temperatures of 0° to 20°C were studied. There was no germination below 11°; germination was near 0 at 11° and reached a maximum at 20°. Achenes equilibrated at 15% moisture generally germinated more rapidly than those at 5% moisture. In hydration-chilling experiments, more than one day of exposure to chilling prior to germination decreased germination and increased the frequency of abnormal seedlings in some entries. Equilibration at 15% moisture prior to chilling reduced damage slightly compared to 5% moisture. There seemed to be a direct relationship between early imbibition rate and susceptibility to chilling damage. Gradual chilling and warming of germinated achenes resulted in a significant reduction in damage compared to abrupt chilling and warming.
John R. Duval and D. Scott NeSmith
Production of triploid watermelon [Citrullus lanatus (Thunb.) Matsum & Nakai] transplants is hindered by poor, inconsistent emergence, and frequent seed coat adherence to cotyledons. Seed coat adherence leads to weakened and slow growing plants. High seed costs, coupled with stand establishment problems, discourages transplant producers from growing this crop. Improvement of triploid watermelon emergence will lessen financial risks to growers and transplant producers and will provide a more reliable production system. Mechanical scarification was evaluated as a means to overcome inconsistent emergence and seed coat adherence. Seeds of `Genesis' triploid watermelon were placed in a cylinder with 100 g of very coarse sand (1.0 to 2.0 mm diameter) and rotated at 60 rpm for 0, 6, 12, 24, and 48 hours in a series of experiments. Number of emerged seed was recorded daily, to obtain emergence dynamics. No significant differences were observed in seed coat adherence among treatments. The longest duration of scarification However, enhanced emergence as compared to the control in three of four experiments. These data support earlier suggestions that a thick or hard seed coat is a factor contributing to poor germination and emergence of triploid watermelons.
T. A. Nell, P. M. Marsh, and D. J. Cantliffe
No differences were observed in water uptake, respiration rate and seed coat morphology of ‘New Era Bright Red’ and ‘New Era Dark Red’ geranium. Water uptake in some seeds was rapid in the first 12 hours following initiation of imbibition. Radicle emergence and germination occurred 3 days after swelling and respiratory activity began as soon as seeds imbibed water. Nonswollen seeds did not germinate. Seed coat surfaces appeared wax-like in both cultivars and no relationship between occlusion of the hilum fissure and germination was observed. Dipping seed in concentrated H2SO4 or hot water, or removing a portion of the seed, increased germination rate and germination to nearly 100%. Results suggest the seed coat in geraniums can be impervious to water uptake.