, limited information is available about the pollinia development of Oncidesa , and there are no reports about the possible roles of anther tissues in relation to the male sterility or low fertility. Histological study on pollinia development is required to
Cheng-Jung Hu, Nean Lee, and Yung-I Lee
D.P.M. Wilson, J.A. Sullivan, A.A. Marsolais, and M.J. Tsujita
The origin and development of somatic embryos from petiole sections of Regal geranium (Pelargonium ×domesticum Bailey `Madame Layal') were studied using time-series sections at days 0, 4, 8, 14, and 24. Somatic embryos originated as early as day 4 of culture. The proembryo stage resembled that of a zygotic embryo and the somatic embryos developed through the globular, heart-torpedo, and cotyledonous stages characteristic of in vivo zygotic embryogenesis. A suspensor-like structure was observed with some somatic embryos but this was not consistent. Strong evidence is presented to suggest that somatic embryos arose from single subepidermal parenchyma cells.
Surawit Wannakrairoj and Haruyuki Kamemoto
James E. Faust, Elizabeth Will, Xian Duan, and Effin T. Graham
Poinsettia stem breakage reduces plant quality and marketability. The cultivar `Freedom' is susceptible to stem breakage; however, the severity of stem breakage varies with crop and year. The following four experiments were conducted to determine the factors that influence stem breakage of `Freedom' poinsettias: 1) Cutting Stem Diameter. Cuttings were graded by stem diameter into small (5.0–5.4 mm), medium (6.0–6.7 mm), and large (7.3–8.3 mm) cuttings. 2) Premature Lateral Shoot Development.Small (1- to 3-cm-long) leaves near the shoot tip of the rooted cuttings were excised to remove the lateral shoots from apical dominance prior to pinching, thus causing the lateral shoots to develop prematurely. 3) Container Spacing. The control group was spaced to 35.6 × 35.6 cm at the time of pinching. The plants in one treatment were spaced to 23.1 × 23.1 cm 25 days after pinching, and then spaced to 35.6 × 35.6 cm 11 days later. The plants in a second treatment were grown pot-to-pot for 36 days after pinch, at which time they were spaced to 35.6 × 35.6 cm. 4) Node Number. Plants were pinched to eight nodes, while the control group was pinched to 5 nodes. Tissue development in the stem crotch; i.e., the area of lateral stem attachment to the main stem, was observed by microscopic examination of paraffin-embedded samples from each experiment every 2 weeks until anthesis. Lateral shoot strength was quantified by hanging a plastic beaker from the lateral stem and gradually adding water until stem crotch failure occurred. We observed that stem strength increased as cutting stem diameter increased. Plants pinched to eight nodes produced weaker lateral shoots than those pinched to five nodes. Premature lateral shoot development and container spacing did not affect stem strength.
Les Frey, Yehoshua Saranga, and Jules Janick
Somatic embryogenesis was induced from internodal callus of `Scania', `Improved White Sim', and `Sandra' carnation (Dianthus caryophyllus L.). The optimum protocol for the induction of somatic embryogenesis included initiation of callus in liquid basal Murashige and Skoog medium supplemented with 3.0 μm 2,4-D followed by transfer to liquid basal medium lacking 2,4-D for embryo development. Somatic embryos originated from single cells and early embryonic development proceeded conventionally (i.e., via globular, heart-shaped, and torpedo stages), but clearly developed apical or root meristems were not always formed. A few embryos developed into seedlings and were acclimatized to ex vitro conditions. Chemical name used: 2,4-dichlorophenoxyacetic acid (2,4-D).
Osamu Arakawa and Joe M. Ogawa
The skin of `Elegant Lady' peach [Prunus persica (L.) Batsch.] fruit turned black when exposed to 100 ppm ferrous sulfate solution. This color change appeared on the red and the yellow portions of the fruit. Microscopy of the skin showed blue-black pigment distribution in epidermal and hypodermal tissues. Some epidermal and hypodermal cells discolored immediately when exposed to ferrous solutions, but many cells turned black later. Some cells with anthocyanin pigments did not discolor. Chromic acid showed that tannic substances were distributed in the epidermal and hypodermal cells, and they likely are the main factor in black discoloration of peach fruit exposed to solutions containing Fe.
Carole H. Saravitz, Frank A. Blazich, and Henry V. Amerson
Hypocotyls of Fraser fir (Abies fraseri (Pursh) Poir.) were excised from seeds germination 9 days and placed on bud induction medium containing 10 mg/liter benzyladenine (BA) and 0.01 mg/liter naphthaleneacetic acid (NAA) or medium without growth regulators. After 3 days on medium containing growth regulators, cell divisions were localized in epidermal and subepidermal layers of the hypocotyl while similar cell divisions were not observed in control-treated hypocotyls. Cell clusters consisting of two to five cells were present after 7 days in hypocotyls placed on bud induction medium. In control-treated hypocotyls, stomata continued to develop and cells within the cortex became vacuolated during the first 2 weeks in culture. All hypocotyls were transferred to secondary medium after 3 weeks. Cell clusters continued to enlarge into meristemoids in hypocotyls initially placed on bud induction medium. Gradually, meristemoids developed into buds and cataphylls were observed covering bud meristems.
Carole H. Saravitz, Frank A. Blazich, and Henry V. Amerson
Cotyledons and hypocotyls of Fraser fir [Abies fraseri (Pursh) Poir.] were excised from seeds treated with H2 O2 for 9 days and placed on bud induction medium containing 10 mg BA/liter and 0.01 mg NAA/liter or medium without growth regulators. Although adventitious buds did not develop, cotyledons exposed to growth regulators responded differently than cotyledons placed on medium lacking growth regulators. Cotyledons and hypocotyls responded similarly to growth regulators during the initial phase in culture, but cell divisions ceased in cotyledons, thus preventing meristemoid and subsequent bud development. After 3 days on medium containing growth regulators cell divisions were localized in epidermal and subjacent layers of hypocotyls, whereas similar cell divisions were' not observed in hypocotyls placed on medium without growth regulators. Cell clusters consisting of two to five cells (promeristemoids) were present after 7 days on hypocotyls placed on bud induction medium. In hypocotyls placed on medium without growth regulators, stomata continued to develop and cells within the cortex became vacuolated during the first 2 weeks in culture. All explants were transferred to secondary medium after 3 weeks. Cell clusters continued to enlarge into meristemoids on hypocotyls initially placed on bud induction medium. Gradually, meristemoids developed into buds and cataphylls were observed covering bud meristems. Chemical names used: N -(phenylmethyl)-1 H -purine-6-amine (BA), 1-naphthaleneacetic acid (NAA).
Ralph Scorzal, Lisa G. May, Beverly Purnell, and Bruce Upchurch
The growth in diameter of large-(`Loring' and `Suncrest') and small-fruited (`Bailey' and `Boone County') peaches [Prunus persica (L.) Batsch] was recorded at weekly intervals from 175 days prebloom to ripening. Samples collected at three dates prebloom, full bloom (FB), and four dates postbloom, including ripe fruit, were sectioned and stained. Total cell count and mean cell size were determined for prebloom ovaries and postbloom mesocarp tissue. Large-fruited cultivars had significantly more cells (up to 3.7 times) than small-fruited cultivars at all sampling dates. Cell sizes increased dramatically with fruit development, but were similar for all cultivars within each sampling date. These results suggest that mesocarp cell count is the major difference between small- and large-fruited peach cultivars and that this difference is determined early in the growth of the ovary.
D.S. Achor, L.G. Albrigo, and C.W. McCoy
Upper surface leaf lesions on `Sunburst' mandarin [(Citrus reticulata Blanco × (C. paradisi Macf. × C. reticulate)] associated with feeding by the citrus rust mite [Phyllocoptruta oleivora (Ashm.)] are more severe than those on other citrus cultivars. Development of leaf lesions on `Sunburst' mandarin and two other cultivars were examined by light and electron microscopy. Damaged leaves treated with a fungicide confirmed that the anatomical changes on `Sunburst' are an enhanced wound periderm response to feeding injury by rust mite and not the result of fungal invasion.