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Green pods of the C. reginae orchid were collected from a bog near Ithaca, NY. Pods were surface sterilized, and seeds were plated on agar media. The 8 germination treatments were arrange in a complete 3 way factorial consisting of 2 basal media (fish emulsion, FE vs. yeast extract, YE), 2 media pHs (4.8, 6.8), and 2 temperature regimes (constant 24 C vs. 6 wks. at 5 C prior to transfer to 24 C). Sequential stages of development included embryo enlargement and rupture of the testa (l), root elongation (2), leaf primordium development (3) and finally rhizoid development with or without protocorm greening (4). After 4 months post sowing, germination (stage 1 or beyond) was 56% and 0% on FE at pH 4.8 and 6.8 respectively, and 45% and 78% on YE at pH 4.8 and 6.8 respectively. Protocorm development from unchilled seeds after 4 months was greatest on YE at the lower pH, with 14% reaching stage 3 or 4, as contrasted to only 5% reaching stage 2 (none beyond), for the other germinated treatments. Chilled seeds had higher germination for all treatments but no development beyond stage 1 at 4 months post sowing.
Abstract
The control of fruit set and development in strawberries (Fragaria X ananassa Duch.) was investigated by exogenous application of auxins to unpollinated flowers or receptacles from which achenes had been removed. Addition of 2% dimethylsulfoxide (DMSO) to aqueous naphthaleneacetic acid (NAA) sprays or dips increased fruit set from ca. 50% to 100%, thus providing a simple and dependable method to induce parthenocarpic fruit set in strawberries. Strawberry fruits were found to be less sensitive to auxin than coleoptiles when auxin-induced strawberry receptacle growth was compared with corn or oat coleoptile elongation. Suboptimal NAA concentrations induced parthenocarpic fruit set with limited fruit growth. Such fruits remained auxin-responsive and viable for 30-45 days when a second NAA treatment resumed their normal growth and development, thus doubling the life span of strawberry fruit from 30 to 60 days. In contrast, unpollinated flowers treated with optimal NAA concentrations in DMSO behaved like pollinated flowers and ripened within 25-30 days. Fifteen auxin analogs and structurally related non-auxins were tested for their ability to stimulate growth of strawberry receptacles following achene removal. The relative effectiveness of these compounds in inducing receptacle growth was very similar, with a few exceptions, to their relative effectiveness in stimulating corn coleoptile elongation.
A protocol is presented that enables a propagator to produce field-sized blueberry transplants within 6 months of obtaining microshoots from tissue culture. The protocol involves subjecting microshoots to ex vitro rooting in a fog chamber under 100 μmol·m–2·s–1 photosynthetic photon flux for 7 weeks, transferring plants to a fog tunnel for 2 weeks, then to a greenhouse for 7 more weeks. Plant survival and rooting of cultivars Berkeley (Vaccinium corymbosum L.) and Northsky (Vaccinium angustifolium ×corymbosum) were near 100% under these conditions. Plantlets in fog chambers receiving 100 μmol·m–2·s–1 grew rapidly, while those at lower irradiance levels grew more slowly, and supplemental CO2 enhanced growth only at 50 μmol·m–2·s–1. Growth rates slowed when plants were moved into the fog tunnel; but by the end of 16 weeks, plants that were under high irradiance in the fog chamber had root systems that were 15 to 30 times larger than plants under low irradiance. Within 6 months, these plants were 30 to 60 cm tall and suitable for field planting.
The effects of four propagation moisture management systems on the water relations and rooting of cuttings of three tropical woody crops were investigated at a relatively cool, but high irradiance site. Leafy semihardwood or leafless hardwood cuttings of Bougainvillea × Buttiana Holtt. & Standl. (bougainvillea), and leafy semihardwood cuttings of Hibiscus rosa-sinensis L. (hibiscus), and Dovyalis caffra (Hook. f. et Harv.) Warb. (kei apple) were propagated in shade under contact tent polyethylene enclosures or in the open with or without intermittent mist. Xylem water potential and leaf and air temperatures and relative humidity were monitored during the rooting period. Hardwood cuttings rooted better than softwood cuttings of bougainvillea. The best rooting of softwood cuttings of all three species was consistently associated with contact polyethylene, whereas open-propagated, nonmisted cuttings rooted poorly or not at all. The poor rooting of open-propagated nonmisted cuttings was associated with the most negative midday ψ and the greatest water vapor density deficit of air surrounding the cuttings (VDDA), but ψ and VDDA were otherwise not consistently associated with success of rooting in other treatments. Midday ψ of cuttings under contact polyethylene was either less negative or not different from that of other treatments despite the fact they exhibited the greatest daytime leaf and leaf to air temperature differences. Because ambient night temperatures were suboptimal for rooting, the warm air trapped beneath the polyethylene enclosures at night may have contributed to improved rooting in these treatments.
Abstract
Effects of several vesicular-arbuscular mycorrhizal (VAM) fungi on shoot growth and mycorrhizal development in ‘Citation’ perennial ryegrass (Lolium perenne L.) were studied as a function of inoculum placement depth. Soil columns were layered with inoculum at 0, 5, 10, or 20 cm prior to seeding. Three inocula were tested: 1) chopped roots and soil from sorghum (Sorghum bicolor L.) plants previously infected with the VAM fungus Glomus macrocarpus Tul. and Tul. var. macrocarpus; 2) a mixed inoculum from plants infected with G. macrocarpus var. macrocarpus; G. mosseae (Nichol. and Gerd.), G. faciculatum (Thaxter) Gerd. and Trappe, Gigaspora margarita Becker and Hall; 3) roots and soil from noninoculated sorghum plants. Shoot growth was greatest when VAM inoculum was placed at the surface, and declined progressively with deeper placement. Greatest mycorrhizal fungal infection of the root system occurred at the site of inoculum placement regardless of depth. The effectiveness of the surface-applied inoculum on enhancing the initial shoot growth (70 days) of perennial ryegrass in this study suggests that inoculation with VAM fungi might prove useful in low maintenance turfgrass culture.