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Abstract

In the article “ Effect of Fruit Removal on Net Gas Exchange of Avocado Leaves”, by Bruce Schaffer, L. Ramos, and S.P. Lara (HortScience 22:925-927, October 1987), ref. 2 was incorrect. The correct citation is: Annu. Rev. Plant Physiol. 33:317-345.

Open Access

Abstract

All but 10 current-year leaves were removed from girdled branches of avocado (Persea americana Mill.) trees having one remaining fruit or all fruit removed. Removing all fruit resulted in increased leaf dry weight per area (Wa), a 250% increase in the number of starch grains in leaves, and a reduction in leaf conductance (gl) and net CO2 assimilation (A). Internal CO2 concentration (Ci) was lower for leaves of branches with fruit than for leaves of branches without fruit. The results suggest that the accumulation of starch in defruited, girdled branches results in an inhibition of A. The data suggest that the increased gl associated with the presence of avocado fruit is possibly a result of increased A and reduced Ci levels.

Open Access

Leaf explants of Coffea arabica cv. Rubi, `Catuaí Vermelho 81', and `IAPAR 59' were placed onto MS basal medium with 4 μm of picloram for 8-12 weeks in the dark at 27 ± 2 °C (standard temperature). Explants (`Rubi' and `Catuaí Vermelho 81') with callus were transferred to a SP basal medium plus 0, 12, 24, and 48 μm BAP, whereas for `IAPAR 59', only 48 μm BAP was added. After 8 weeks for `Rubi' and `Catuaí Vermelho 81' and after 12 weeks for `IAPAR 59', all cultivars showed indirect embryogenesis. Embryogenic material was transferred to a SP basal medium without BAP, in light (16-hour photoperiod) and standard temperature. In a second experiment, leaf explants belonging to all three cultivars were inoculated in petri dishes with SP basal medium plus 0, 2.5 and 5 μm BAP, in the dark at standard temperature. After 8 weeks, only `IAPAR 59' produced direct embryos. These were transferred to SP basal medium. About 30% of embryos developed abnormalities. Normal embryos were successfully transferred to soil.

Free access

Spectral reflectance measurements were taken from immature and mature leaves of `Rio Red' grapefruit `McCarty' grapefruit `Minneola' tangelo, `Satsuma' mandarin, `Dancy' tangerine, `Nagami' oval kumquat, and `Valencia' orange from 1330 to 1530 hr 1 day at the Florida Citrus Arboretum, Division of Plant Industry, Winter Haven, Fla. A PS-1000 spectrometer was used with fiber optic cables and a lens source (visible range of the spectrum 400-800 sun) coupled with a tungsten halogen light source. A data acquisition card was connected to a notebook computer with a SpectraScope computer program for processing and data storage. Immature and mature leaves of `Minneola' tangelo had greater percentage reflectance in the 500-800 sun range than the other cultivars and leaf ages measured. More detailed information was obtained with the PS-1000 than with conventional spectrometers. The slope of the citrus spectral curves in the 800 nm range was not as sharp as conventional spectrometers, but had a much higher reflectance value than those obtained with a different spectrometer. The system used here was convenient to transport and use in the field and produced clear, interpretable data.

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Abstract

Phenological stages of ‘Flora-Dade’ tomatoes are described using a nomenclature system to be used for tomato pest management. Two vegetative stages (TV1, TV2) are listed as well as 3 reproductive plant stages (TR1, TR2, and TR3). Vegetative stage TV1 describes plants 1–15–days old with 2–3 primary leaves. TV2 describes plants 6–39 days–old with 5–7 leaves. Reproductive stages (TR1 TR2, and TR3) cover plants 40–135 days–old, characterized by presence of flowers clusters, and fruit formation and ripening. Characteristics of each stage are discussed. A senescent stage (TS1) is present from 136–200 days after plant emergence.

Open Access

Abstract

Foliar sprays of (2-chloroethyl)phosphonic acid (ethephon) were applied at 50, 100, and 150 ppm to French prune trees at 50% petal fall and when seed length was 8.3 to 9.4 mm. All concentrations thinned fruits within 3 to 4 weeks after treatment. The treatments increased soluble solids and fruit size, and in some instances decreased dry tonnage. Return bloom the following year was greater on treated trees than on controls. Also, fall coloration patterns appeared earlier on the treated trees. No phytotoxic effects from the treatments were evident on the fruits.

Open Access

To be useful for indicating plant water needs, any measure of plant stress should be closely related to some of the known short- and medium-term plant stress responses, such as stomatal closure and reduced rates of expansive growth. Midday stem water potential has proven to be a useful index of stress in a number of fruit tree species. Day-to-day fluctuations in stem water potential under well-irrigated conditions are well correlated with midday vapor-pressure deficit, and, hence, a nonstressed baseline can be predicted. Measuring stem water potential helped explain the results of a 3-year deficit irrigation study in mature prunes, which showed that deficit irrigation could have either positive or negative impacts on tree productivity, depending on soil conditions. Mild to moderate water stress was economically beneficial. In almond, stem water potential was closely related to overall tree growth as measured by increases in trunk cross-sectional area. In cherry, stem water potential was correlated with leaf stomatal conductance and rates of shoot growth, with shoot growth essentially stopping once stem water potential dropped to between −1.5 to −1.7 MPa. In pear, fruit size and other fruit quality attributes (soluble solids, color) were all closely associated with stem water potential. In many of these field studies, systematic tree-to-tree differences in water status were large enough to obscure irrigation treatment effects. Hence, in the absence of a plant-based measure of water stress, it may be difficult to determine whether the lack of an irrigation treatment effect indicates the lack of a physiological response to plant water status, or rather is due to treatment ineffectiveness in influencing plant water status. These data indicate that stem water potential can be used to quantify stress reliably and guide irrigation decisions on a site-specific basis.

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