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- Author or Editor: Vito S. Polito x
Abstract
Intracellular Ca2+ and regulation of cell Ca2+ play important roles in cell development and in the maintenance and modulation of various cell functions. This report will describe research on the role of membrane and free cytoplasmic Ca2+ in cell development and stress tolerance. Results to be presented include microscopic fluorometric data obtained using fluorescent probes for Ca2+ and cytoskeletal proteins within individual cells to investigate the role of Ca2+ in membrane organization, establishment of cell polarity, and maintenance of cytoplasmic streaming under stress conditions.
We investigated pollination and fruit set parameters in `Manzanillo' olive (Olea europaea L.) following self-pollination and pollination with `Sevillano', `Ascolano', and `Mission' pollen. Results of analyses and experiments conducted over 2 years in central California indicated that `Manzanillo' behaves as a self-incompatible cultivar (index of self-incompatibility = 0.22 to 0.24). Pollination with `Sevillano' resulted in a more than 4-fold increase in fruit set over self-pollination. When `Mission' or `Ascolano' pollen was used, there was no increase over self-pollinated samples. Analyses of pollen tube growth, fertilization, initial fruit set, and final fruit set were consistent with `Manzanillo' being considered as a self-incompatible cultivar cross-incompatible with `Mission' and `Ascolano'. Our results indicate that `Manzanillo' is likely to be more productive when interplanted with `Sevillano' rather than when planted without a pollinizer or with `Mission' or `Ascolano'.
Abstract
Pistachio (Pistacia vera L.) pollen was examined for capacity to germinate in vitro 2 days after anthesis and at intervals of time after storage at ambient laboratory conditions or at − 20°C. In 1986, fresh pollen of each of four clones examined had high germination percentages on a range of sucrose and agar concentrations. After 1 week at room temperature, germination percentages were < 6%. However, when the same week-old pollen was treated to effect gradual hydration at high humidity prior to being placed on the germination medium, germination increased to > 80% for ‘Peters’ pollen and 10.4% to 63.8% for the three other clones. In 1987, similar results were obtained for ‘Peters’ pollen, where pollen hydrated at high humidity had germination rates at least 50% that of fresh pollen when stored up to 18 days at ambient laboratory temperature and humidity. Pollen stored at −20° showed more exacting in vitro germination requirements than fresh pollen, particularly as time in storage increased. ‘Peters’ pollen retained germination levels comparable to fresh pollen after 4 months at −20°, but, by 12 months, germination percentages had fallen sharply.
Abstract
Five to 6 weeks elapsed between full bloom and zygote division of ‘Kerman’ pistachio (Pistacia vera L.). Various patterns of cell division in the proembryo, after transverse division in the zygote, brought about formation of a globular to heart-shaped embryo in the following 3–4 weeks. Cell enlargement in the cotyledons during the subsequent 4–5 weeks contributed mainly to final embryo size. The transition from free-nuclear to cellular endosperm was not limited to a definite stage of embryo development. The endosperm was almost digested by the time the embryo reached its ultimate size.
Bronzing of strawberry (Fragaria ×ananassa Duchesne) fruit that is not the result of arthropod feeding or chemical spray application occurs frequently in California's central coast strawberry production region from late spring through midsummer, a period characterized by relatively high temperature, low relative humidity, and high solar irradiance. The cause of this phenomenon is not known, but in preliminary trials, intermittent, midday misting of plants and increased drip irrigation rate resulted in reduced incidence of fruit bronzing. To characterize the bronzing phenomenon and its development in strawberry fruit tissues, we conducted an anatomical and histochemical examination of bronzed fruit. Bronzed and nonbronzed fruit were sampled over a range of fruit maturities. Results show that bronzing derives from a lesion at the cortical surface early in the fruit's development. Epidermal cells become radially compressed and the cell contents coalesce into a densely staining mass. The cuticular layer becomes disrupted and discontinuous. As the fruit develops, densely staining materials, possibly phenolic precipitates, accumulate within subepidermal cells of bronzed fruit, subepidermal cell walls thicken, and intercellular spaces fill with pectic substances and other densely staining materials. Results are consistent with reports of sunscald injury from other fruit species, and raise the possibility that strawberry bronzing occurs in response to heat or solar radiation injury.
Abstract
In pistachio (Pistacia vera L. cv. Kerman), when flowers did not set or when young fruits were removed, pedicels and/or portions of the rachis or of the primary branches subtending these parts abscised. Inflorescence buds on fruiting shoots and those on nonbearing shoots treated with (2-chloroethyl) phosphonic acid (ethephon) also abscised. Abscission of the above organs, as well as of leaflets and compound leaves, occurred in definite zones. The first manifestation of the abscission process was transverse cell division in the abscission zone. A separation layer developed in the distal portion of the abscission zone in these organs. The newly formed cells in the proximal area of the abscission zone of pedicels, rachises, and ethephon-treated inflorescence buds became protective layers. However, the counterpart in abscising inflorescence buds on fruiting shoots was largely degraded as abscission progressed. Abscission of mature fruits of pistachio was not preceded by cell division but involved separation and collapse of cells in the fruit mesocarp and exocarp surrounding the distal portion of the pedicel.
Experiments were conducted to determine if differential responses of walnut pollen germination to temperature, previously observed to occur among genotypes, were genetically fixed or expressions of phenotypic plasticity representing adaptive responses to temperatures experienced during pollen development. Individual branches of a single walnut (Juglans regia L. cv. Serr) tree were warmed above ambient conditions during the final stages of pollen differentiation by directing a stream of moist, heated air into polyethylene enclosures, each containing an individual branch unit. Pollen was collected at staminate anthesis and incubated in germination medium on a temperature gradient apparatus. Model curves fitted to the in vitro pollen germination data were used to determine optimum germination temperatures. We found adaptive responses of pollen germination to temperatures experienced during pollen development. The optimum temperature for in vitro germination for pollen from branches maintained under ambient conditions was lower than that of pollen from branches with elevated temperature, and optimum germination temperature increased as a log function of integrated daily temperature (degree-days) experienced during pollen development.
Walnut Blight caused by the bacteria Xanthomonas campestris pathovar juglandis is a very destructive disease for California walnut production. Streptomycin is an effective disease control material; however, Streptomycin sprays can result in significant nut drop 3 to 5 weeks after spray application. We investigated the basis for walnut drop following applications of Streptomycin (Agrimycin) for walnut blight control. Flowers and developing nuts were collected from four treatments, plus an unsprayed control. 200 ppm Streptomycim was applied at 1) budbreak; 2) pre, full, and post-bloom; 3) postbloom; 4) budbreak and postbloom; 5) untreated control. Samples were collected regularly beginning at the first budbreak spray and extending through the period of nut drop. Samples were fixed and prepared for histological examination. In treatments with a high incidence of nut drop, the embryo failed to develop. Examination of the stigma and style in flowers from these treatments showed inhibited pollen tube growth. Results indicate that Streptomycin inhibits pollen tube growth, which precludes fertilization. This pattern of development and timing of nut drop following Streptomycin application at full bloom is similar in all ways to unpollinated walnut flowers. Nut growth and development appear normal for 3 to 5 weeks; then nuts abort. If Streptomycin became available for walnut blight control, sprays timed to coincide with pistillate bloom and pistillate flower receptivity should be avoided.
A comparative study was conducted to evaluate the influence of seven different levels of irrigation applied to `Arbequina I-18' olive (Olea europaea L.) trees grown in a super-high-density orchard (1,656 trees/ha) in the Sacramento Valley of California. Water was applied differentially by drip irrigation at rates of 15%, 25%, 40%, 57%, 71%, 89%, and 107% evapotranspiration (ETc) in 2002, and 28%, 33%, 55%, 74%, 93%, 117%, and 140% ETc in 2003. Each treatment was replicated three times. Olives were harvested on two different dates each year from each of 21 plots. Three of four harvest dates showed a decrease in maturity index with increasing irrigation levels. Oils were made from olive samples collected from each plot and analyzed for oil quality parameters. Total polyphenol levels and oxidative stability decreased as the trees received more water, especially for the three lowest irrigation treatment levels in 2002, but few differences were noted between treatments in 2003 when all the trees were irrigated more heavily. Average oxidative stability was correlated very closely with total polyphenol content with r 2 = 0.98 in 2002 and 0.94 in 2003. In 2002, free fatty acid levels increased and peroxide levels were unchanged, but in 2003, free fatty acid levels were unchanged and peroxide levels decreased in treatments receiving more water. Saturated fatty acids did not significantly change in 2002, due to tree irrigation level. The mono-unsaturated fatty acid levels and oleic–linoleic relationship declined while poly-unsaturated fatty acid levels increased in 2002 with increased irrigation. In 2003, there was no notable difference in the ratio of mono to poly unsaturated fatty acid levels. The individual fatty acid most consistently affected by more irrigation water was stearic, which decreased in both years. Total sterol content (mg·kg–1), percentages of cholesterol and erythrodiol were significantly influenced by tree irrigation levels, but increased in one year and either decreased or were unchanged the next. Oil sensory properties of fruitiness, bitterness, and pungency all declined in oils made from trees receiving more water. The lowest irrigation levels produced oils that were characterized by excessive bitterness, very high pungency, and woody, herbaceous flavors. Intermediate irrigation levels (33% to 40% ETc) produced oils with balance, complexity, and characteristic artichoke, grass, green apple, and some ripe fruit flavors. Higher irrigation levels lowered oil extractability and produced relatively bland oils with significantly less fruitiness and almost no bitterness or pungency.
The role of pollen in abscission of pistillate flowers of Persian walnut (Juglans regia L.) cv. Serr was investigated over a 4-year period by controlled pollinations and pollen counts. Self-pollen, pollen from other walnut selections or cultivars, or dead pollen was applied at high and low doses to pistillate flowers enclosed in pollination bags. Unbagged, open-pollinated flowers and bagged, nonpollinated flowers served as controls. In all cases, presence of pollen significantly increased the probability of pistillate flower abscission (PFA). Dead pollen resulted in as much PFA as live pollen. Counts of pollen grains confirmed that PFA-type flowers had significantly more pollen than normal flowers. In the fourth year `Serr' pollen was applied to unbagged flowers of `Serr' and ten other Persian walnut cultivars, and the amount of PFA on the artificially pollinated flowers was significantly higher than on the open-pollinated flowers, while the control flowers dusted with talc or pine pollen had almost no PFA. These results clearly indicate that excess pollen is involved in pistillate flower abscission in `Serr' walnut and suggests that other cultivars may also be sensitive to pollen load. This phenomenon may have implications in the biology of selfing and evolution.