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Abstract

The CO2 assimilation characteristics of walnut leaves (Juglans regia L.) were measured on excised branches using controlled, open-system, infrared gas analysis techniques in the laboratory and on large bearing trees with a CO2 depletion method in the field. The mean maximum rate of net CO2 assimilation measured by both techniques was 1.3 nM CO2 cm-2s-l on a leaf area basis of 6.0 nm CO2 mg N-1s-1 on a leaf nitrogen basis. Leaves approached light saturation at 600-800 µEs-1m-2, and exhibited an otpimum range for CO2 assimilation at 18 to 26°C. CO2 assimilation increased linearly with increases in intercellular CO2 concentrations between 60-250 µl liter-1. The daily pattern of field CO2 assimilation was highly correlated with leaf conductance to H2O but exhibited a midday depression that was independent of the daily pattern of incident photosynthetic photon flux density at the surface of the leaves.

Open Access

Abstract

Leaf number, area and chlorophyll content, and specific leaf weight were greater in light-exposed spurs of ‘Hartley’ walnut (Juglans regia L.) than those grown in the shade. Starch content increased early in the season in shaded spurs, but the accumulation ceased while the nuts stored dry matter. In exposed spurs, starch increased steadily until harvest. After harvest, starch level decreased in exposed and shaded spurs. Light intensity did not affect percentage composition of spurs and fruit with respect to carbohydrates or oil content in kernels. Increased exposure to light resulted in higher percentage of return bloom, greater spur growth, and more pistillate flowers per spur the following season.

Open Access

Cotyledon explants of walnut (Juglans regia) have been shown to generate adventitious roots on growth regulator-free medium. The spatial distribution of endogenous indole-3-acetic acid (IAA) and its dynamic changes during adventitious root formation were investigated using an in situ immunohistochemical approach. Before root induction, IAA signal was distributed throughout the freshly excised cotyledon explants. During provascular bundle differentiation, the IAA signal was mainly located in the provascular bundles. At the stage of annular meristematic zones formation, the IAA signal was mainly distributed in the meristematic zones and decreased in the vascular bundles and cotyledonous parenchyma. As primordia formed, the IAA signal became localized in the root primordia and gradually disappeared in the meristematic zones. In emerging roots, the IAA signal was mainly localized in the root cap and root meristem. These results suggest that accumulation of IAA in the provascular bundles may induce vascular differentiation and the increase in IAA through meristematic zones may be responsible for the adventitious root formation from walnut cotyledons. The direct evidence presented here indicates that IAA accumulated in the meristematic zones is not the sole signal needed to induce adventitious root.

Free access

Slovene domestic population of Persian walnut ( Juglans regia L.). ‘Sava’ was tested as ‘Zdole-59’ and ‘Krka’ as ‘Erjavec’ ( Solar and Stampar, 2006 ). Because the original trees grow in the vicinity of rivers Sava and Krka, the new cultivars were named

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Department of Food and Agriculture ( CDFA) 2021 ]. Almond ( Prunus dulcis ) and walnut ( Juglans regia ) account for more than 1.6 million acres of this crop sector ( CDFA 2021 ). Weed management is a critical challenge for orchard growers, although the

Open Access

suitable for the soil and climatic conditions of Greece. Through these endeavors and specific crosses, a lateral-bearing cultivar has emerged with satisfactory characteristics: ‘Ourania’. This is a new walnut ( Juglans regia ) cultivar of Greek origin

Open Access

Abstract

Quantitative assessments of the degree of susceptibility to experimental infection by Erwinia rubrifaciens Wilson et al. were made on 54 cultivars of Juglans regia L., J. hindsii Jepson, and J. nigra L. on J. hindsii and Paradox rootstocks. Forty-five of the 54 cultivars were susceptible and developed symptoms characteristic of deep bark canker. On Paradox rootstock, ‘Pioneer,’ ‘Early Erhardt,’ ‘Willson-Franquette,’ ‘Sinensisy5,’ ‘Conway-Mayette,’ ‘Scharsch-Franquette,’ ‘Meylan,’ and ‘Sinensis-7’ showed canker extension rates greater than ‘Hartley’; whereas, on J. hindsii rootstock only ‘Sinensis-5’ and ‘Sinensis-7’ showed canker extension rates greater than ‘Hartley.’ All cultivars were ranked into 4 susceptibility groups according to their rates of canker extension: group I (0 mm/day), group II (0.01 to 0.10 mm/day), group III (0.101 to 0.200 mm/day) and group IV (0.201 to 1.0 or greater mm/day). Of 54 cultivars only 8 ranked in group I (non-susceptible); 28 ranked in group II (dry-canker types); 11 ranked in group III (moderately susceptible); and 7 ranked in group IV (highly susceptible). ‘Hartley,’ the only cultivar commonly associated with the disease in commercial plantings ranked in group IV. Cultivars of either J. hindsii or J. nigra were ranked in group I. Erwinia rubrifaciens was recovered from 45 of 54 cultivars, 14 months after experimental inoculation and 23 of 54 cultivars after 26 months. The pathogenic bacterium was recovered from cultivars of group I (that displayed no visible symptoms). It is hypothesized that natural populations of J. hindsii and J. nigra may harbor E. rubrifaciens and may have been the original inoculum source.

Open Access
Author:

ders notları. KSU Ziraat Fakültesi, Kahramanmaraş, Turkey. UPOV 1999 Union internationale pour le protection des obtentions vegetales draft guidelines for the conduct of tests for distinctness, uniformity and stability walnut ( Juglans regia L.), TG

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Walnut ( Juglans regia L.) is one of the most important fruit species in the world because it is rich in nutrients and elements, and is a high-quality wood. There is an increasing interest by consumers in eating walnuts, especially in Middle

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cultivars, including Payne, Franquette, Sunland, and Chico, were introduced into China during 1992–95, but they were unable to survive the cold winter in Liaoning province. ‘Liaoning 1’ was released as a new Persian walnut ( Juglans regia L.) cultivar in

Open Access