Abstract
The heart-shaped embryos, dissected from mature fruits of 11 Ilex (holly) species in 4 taxonomic sections, grown in modified White’s and Linsmaier and Skoog’s media jelled with Bacto-agar, produced seedlings. The rudimentary embryos were sufficiently autotrophic that a carbon source was the only organic compound needed in the media. There is a great variation in speed of in vitro development among individual embryos of the same species. The average embryo length of I. aquifolium L. increased linearly and most embryos reached germination size at the 55th day of incubation. The average embryo length of I. cornuta Lindl. increased sigmoidally and most embryos reached germination size at the 23rd day of incubation. The in vitro germination percentages for most species were above 80%. The survival rates after transplanting were higher than 75%. Sub-sequent seedling growth in greenhouses was healthy and vigorous.
Alternate bloom thinners are needed for apple are needed to replace compounds which can no longer be used or have production system limitations. The effects of 24 chemicals selected as osmotic agents, organic acids, oils, essential oils, or potential metabolic agents and their properties of pH, electrical potential (EP) and water potential were tested in vitro on `Gala' apple pollen germination, tube growth and pistil damage. Solution concentrations of 0%, 0.25%, 0.5%, 1%, 2%, 5%, and 10% were prepared and solution pH, EP, and water potential measured. To test affects on germination, pollen was placed on agar germination media in petri dishes and then treated with 10: l of chemical solution. Percentage pollen germination and tube growth was calculated 4, 12, and 24 h after treatment. Excised pistils from forced flowers were placed on glass filter papers saturated with chemical solution. Pistil damage was visually, subjectively rated for damage indicated by discoloration 24 h after treatment. Effects of solution pH, EP and water potential on pollen germination, tube growth and pistil damage was significant with pH less than ∂4.0 or greater than ∂10.0, EP > 200mv, or water potential less than ∼4.0MPa inhibited pollen germination, growth, and killed pistils. Several chemical had apparent metabolic effects beyond the chemical effects mentioned above. In vitro tests were correlated to in vivo field tests in other studies indicating the use of pollen and pistil in vitro as a useful model for screening potential alternative thinning agents.
Abstract
In short-term exposure studies pollen from several tuber-bearing Solanum species retained high viability after rapid cooling in liquid nitrogen, provided the initial moisture content was less than 35–40%. Some pollen samples dried over anhydrous CaCl2 to low moisture levels required rehydration before assessing germination in vitro.
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Accessions of Vaccinium species (deliciosum, ovalifolium, membranaceum, parvifolium, scoparium) were evaluated for tolerance to higher pH in the root zone using an in vitro screening procedure. Seeds were germinated on media containing all essential nutrients with nitrogen in the nitrate form at pH 5 and pH 6 and evaluated for 21 weeks. Excess EDTA was used to buffer the micronutrients and pH was buffered by MES and succinic acid. Germination varied among species with V. ovalifolium being highest and V. parvifolium not germinating at all. Mortality was lower at pH 5. At pH 6, V. ovalifolium and V. membranaceum exhibited variation for growth while all other species suffered complete mortality.
The occurrence of bacteria in different tissues was studied using field-grown strawberries, in vitro-grown strawberries, wild strawberries, and aseptically germinated strawberry seedlings. Strawberry has a number of endophytic bacteria in its the internal tissue, most of which appear to be nonpathogenic. In the in vitro-grown strawberries, all identified isolates were in the genus Pantoea. In field-grown garden and wild strawberries the most common genera were Pantoea and Pseudomonas. Location of eubacterial inhabitants within strawberry tissue sections was studied by in situ hybridization. Bacteria were detected in flower stalks, leaf stalks, leaves, stolons, berries and aseptically germinated seedlings. The existence of bacteria in seeds and seedlings suggests that bacteria are able to move up to the generative tissue and, ultimately, to the next generation, forming a symbiosis-like chain of plant-bacteria coexistence.
Abbreviation: FDA, flourescein diacetate. I thank Monika Shah for technical assistance. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked
Abstract
Blackberry pollen germination in vitro decreased linearly with increased duration of storage at 22°C. Time required to reach 50% nonviability varied among cultivars from 2.5 to 10 days. Storage at 6° more than doubled the time required to reach 50% non viability. A 20% sucrose-agar medium was satisfactory for germination assay of pollen from tetraploid blackberries but gave poor results on a diploid clone.
Volatile compounds, commonly produced by flowers during bloom, have been described as insect attractants. Some of these compounds stimulate Pinus pollen germination in vitro (French et al., 1979, J. Agric. Fd. Chem., 27184-187), suggesting that such compounds may do the same in vivo. Red Delicious apple pollen was germinated on agar in a simple, enclosed in vitro bioassay system in the presence of a number of plant tissues, including apple, tomato, and chrysanthemum leaves, apple flowers, rose petals, and apple fruit slices. These tissues represent a diversity of types of volatile compounds, Pollen germination was recorded by microphotography after 1 and 2 hours, and percent germination was determined. Although stimulation of germination was not observed, macerated tomato leaves inhibited it. To determine if the volatile characteristics of cultivars differ, flowers of Red Delicious and Golden Delicious apple were harvested at full bloom. Their volatiles were collected, identified, and quantitated by capillary GC-MS. Among 8 major compounds common in the two cultivars, several quantitative differences were observed. These results will be discussed in relation to the potential role of volatiles in pollen germination.
To develop In vitro techniques to overcome incompatibility in sweetpotato the cross and self incompatible cultivars Regal and MD-708 were cross pollinated and also crossed with the compatible `Vardaman'. Observation of pollen behavior in different crosses after 3, 7, and 24 hours, showed good germination and tube development in compatible crosses, but no germination in incompatibles. In a preliminary experiment using embryo rescue techniques plants were produced only from compatible crosses at 25 and 30 days after pollination. In subsequent experiments, immature embryos were rescued when cultured 15 days after pollination. The highest percentage of rescued embryos resulted from Murashige-Skoog medium. Intraovarian, stigmatic and placental in vitro fertilization were investigated to overcome incompatibility. Embryos were not formed from any of those methods, but callus was produced with placental pollination.