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  • Author or Editor: R.B. Jones x
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Abstract

Mouse ear is an abnormal condition in pecans [Carya illinoensis (Wang.) K. Koch] in which the leaflets of the compound leaf fail to elongate in a normal manner and develop into a “mouse ear” shape. Mouse-ear trees had more Ca, Mn, Fe, Cu, Zn and Mo and less Mg in leaf and stem tissues than normal trees. In both normal and mouse ear pecan, 92–96% of total Ca in leaves and stems was nonextractable in 2% acetic acid solution, being in the form of Ca-oxalate crystals. Crystals of cross-sectional area as large as 2000 μm2 and 6000 μm2 were found in leaves and stems, respectively. Although only 600 to 1200 ppm of Ca was available for physiological functions in leaf tissue other than for precipitation of oxalic acid. There was no significant evidence to show that mouse ear is a Ca-deficiency problem.

Open Access

Abstract

Soils, and leaf and fruit tissues were collected from 200 peach orchard sites during the 1970 growing season. Results obtained were not markedly different from those obtained in an earlier survey in 1962. Most of the soils were quite acid and the peach leaf N levels were below optimum. Most growers appeared to be overfertilizing with P but applying adequate K. Peach fruit were quite high in K, accounting for a sizeable removal of K from the soil.

Open Access

Abstract

Most of the leaf Ca collected from healthy and declining peach trees (Prunus persica L. Batsch. cv. Loring) growing on both limed and unlimed field plots was found to be non-extractable in acetic acid irrespective of leaf age, health status, or lime treatment. The concentration of extractable leaf Ca was less than 100 parts per million. Concentration of total Ca was highest in leaves from declining trees but declining trees had fewer and smaller leaves resulting in less total Ca in decline as compared to healthy trees. Large numbers of Ca-oxalate crystals were observed throughout the leaf and stem tissues. Crystals were primarily concentrated in leaf midveins. Midvein sections of leaves from decline trees contained greater numbers of crystals per unit area than did those from healthy leaves from healthy trees.

Open Access

Abstract

Glasshouse microclimate during 3 growth periods in the Southern Piedmont region of the United States was characterized. An increase in density of tomato plants (Lycopersicon esculentum Mill.) by one-third, which doubled radiation interception, was suggested by early observations. Maintenance of clean glass surfaces was found to be particularly important during cloudy weather. There was no significant difference between mean air temperature and mean rooting media temperature in the raised beds used. CO2 concentration was found to be low (240 ppm) when fans were not circulating outside air. CO2 generators, installed to increase greenhouse CO2 levels, were not effective possibly because control was inadequate. The use of CO2 enrichment requires further study under Southeastern conditions. Relative humidity remained below the recommended 90% in the green-house except during cloudy-mild weather. Although inside relative humidity was generally less than outside relative humidity, values ranged from 90 to 100%.

Open Access

Tomato (Lycopersicon esculentum Mill.) accessions were tested for hypersensitivity and rated for resistance following field inoculation with tomato race 3 (T3) of the bacterial spot pathogen Xanthomonas campestris pv. vesicatoria (Doidge) Dye (Xcv) in 1992 and 1993. Hawaii 7981, PI 126932, PI 128216, and selections of the latter two expressed hypersensitivity. Hawaii 7981, only tested in the field in 1993, was nearly symptomless and developed significantly less disease than any other accession. PI 128216 had a level of disease similar to susceptible `Solar Set' when tested in 1993. However, a selection from it (PI 126218-S) was significantly more resistant than `Solar Set' in both years. Although PI 126932 had a level of disease similar to `Solar Set' in both years, a selection from it (PI 126932-1-2) was significantly more resistant than `Solar Set' in 1993. Other accessions without hypersensitive responses but more resistant than `Solar Set' for two seasons were PI 114490, PI 126428, PI 340905-S, and PI 155372. Hawaii 7975 was significantly more resistant than `Solar Set' in the one season it was tested.

Free access

Available water for urban landscape irrigation is likely to become more limited because of inadequate precipitation and the ever-increasing water demand of a growing population. Recent droughts in the western United States have also increased the demand for low-water-use landscapes in urban areas. Penstemon species (beardtongues) are ornamental perennials commonly grown in low-water-use landscapes, but their drought tolerance has not been widely investigated. The objectives of this study were to determine the effects of water availability on the morphology, physiology, and canopy temperature of Penstemon barbatus (Cav.) Roth ‘Novapenblu’ (Rock Candy Blue® penstemon), P. digitalis Nutt. ex Sims ‘TNPENDB’ (Dakota™ Burgundy beardtongue), P. ×mexicali Mitch. ‘P007S’ (Pikes Peak Purple® penstemon), and P. strictus Benth. (Rocky Mountain penstemon). Twenty-four plants of each penstemon species were randomly assigned to blocks in an automated irrigation system, and the substrate volumetric water content was maintained at 0.15 or 0.35 m3⋅m−3 for 50 days. The decreased substrate volumetric water content resulted in a decreased aesthetic appearance of the four penstemon species because of the increased numbers of visibly wilted leaves and chlorosis. Plant growth index [(height + (width 1 + width 2)/2)/2], shoot number, shoot dry weight, leaf size, and total leaf area also decreased as the substrate volumetric water content decreased, but the root-to-shoot ratio and leaf thickness increased. Photosynthesis decreased, stomatal resistance increased, and warmer canopy temperatures were observed when plants were dehydrated. Additionally, as substrate volumetric water content decreased, the leaf reflectance of P. barbatus and P. strictus increased. Penstemon digitalis, which had the highest canopy–air temperature difference, was sensitive to drought stress, exhibiting a large proportion of visibly wilted leaves. Penstemon ×mexicali, which had the lowest root-to-shoot ratio, had the lowest shoot water content of the species studied and more than 65% of leaves visibly wilted when experiencing drought stress. Penstemon barbatus and P. strictus, native to arid regions, exhibited lower canopy–air temperature differences and better aesthetic quality than the other two species. Under the conditions of this study, Penstemon barbatus and P. strictus exhibited better drought tolerance than P. digitalis and P. ×mexicali.

Open Access

Abstract

Spraying with 3% ethyl oleate (EO) reduced the incidence of cracking from 29 to 11% in ‘Vista’ cherries (Prunis avium L.) Applications of EO increased the rate of dehydration in cherries exposed to ambient air following treatment. Scanning electron microscopy (SEM) observations suggest that EO modifies the cherry cuticle by redistributing surface wax, thereby enhancing mass transfer of water vapor through the skin.

Open Access

Thirty-two tomato (Lycopersicon esculentum Mill.) or L. pimpinellifolium (L.) Mill. accessions were inoculated with race T2 of Xanthomonas campestris pv. vesicatoria (Xcv) in a field experiment at Wooster, Ohio, in 1995. Plants from accessions which segregated for race T2 resistance in greenhouse tests were selected and these are designated by hyphenated extensions below. The eight most resistant accessions from 1995 and PI 262173 were retested in 1996. Lycopersicon esculentum accession PI 114490-1-1 had virtually no Xcv symptoms either year. Lycopersicon pimpinellifolium accessions LA 442-1-Bk and PI 128216-T2 expressed a high level of resistance in 1995, but only partial resistance in 1996. Accessions with partial resistance for both seasons were PI 79532-S1, PI 155372-S1, PI 126428, PI 271385, PI 195002, PI 262173, Hawaii 7998, and Hawaii 7983. PI 79532-S1 is a L. pimpinellifolium accession and the remaining seven are L. esculentum. Twenty accessions tested in 1995 for T2 plus 10 other accessions were also tested for race T1 resistance in Presidente Prudente, Sao Paulo, Brazil, in 1993. Hawaii 7983, PI 155372-S1, PI 114490, PI 114490-S1, and PI 262173 had greater resistance to T1 than the susceptible control, `Solar Set'. Comparisons with earlier experiments, in which accessions were inoculated with race T1 or T3, indicated that the most consistent source of resistance to all three races was PI 114490 or selections derived from it.

Free access

Abstract

Field studies were conducted over three seasons to determine the effect of N and K on susceptibility of tomato to bacterial spot. A factorial randomized complete block design consisting of four rates of N (167, 334, 501, and 668 kg·ha–1) and three rates of K (334, 668, and 1335 kg·ha–1) were used. Liquid fertilizer was injected via trickle irrigation. Increasing N rates reduced disease severity, whereas the effect of increasing K was inconsistent from season to season. The concentration of N in leaf tissue showed a significant negative correlation with disease severity, whereas the concentration of Ca in leaf tissue exhibited significant positive correlation with disease severity and negative correlation with N rate during two seasons of data collection.

Open Access