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M. Elena Garcia, C.R. Rom, and J.B. Murphy

Two experiments were conducted to determine the effects of leaf age and shading on the phenolic content and composition of apple foliage. In the first study, it was determined that the phenolic content of `Liberty', at increasing leaf developmental stages, was leaf age—dependent. Early during leaf development, there was an increase in the phloridzin (the primary glycoside identified) and in total phenolics, reaching a maximum when the leaf is 6 days from 20-mm blade length. After this stage, the phenolic content decreased with increasing leaf age. In the second study, the leaves of two cultivars, `Liberty' and `Starkspur Law Rome', were tagged weekly when the leaf was two-thirds unfolded. Three weeks after budbreak, the trees were placed under three shade cloth treatments (0%, 60%, and 90% shade). After 4 weeks under the shade treatments, the tagged leaves were collected to determine their phenolic content. Shade significantly affected the foliar phenolic content. Leaves in 0% shade had the highest phenolic content, whereas the lowest content was found in leaves exposed to 90% shade. There was a significant leaf age × shade interaction. The phenolic content decreased with increasing leaf age except for those leaves whose development occurred before the experiment was started. The results indicate that light and leaf developmental stage are important factors in determining the phenolic content of apple leaves, but shading appears to have a stronger influence than leaf developmental stage. E-mail mgarcia@zoo.uvm.edu; phone (802) 656-2824.

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Dale T. Lindgren and Daniel M. Schaaf

Studies were conducted to evaluate the effect of stratification and seed age on percent seedling emergence of Penstemon. Emergence differences occurred between the eight Penstemon selections, as well as between seed stratification treatments and seed age. Seed stratification significantly increased emergence. Emergence varied from 0% with 1-year-old seed of Penstemon digitalis with no stratification, to 72.8% emergence with 2-year-old seed of P. angustifolius with 10 weeks of stratification. Seedlings from 3- to 4-year-old seed generally emerged as well as or better than with 1- and 2-year-old seed. Percent emergence varied significantly with stratification, seed age, and species. Some emergence occurred with species from seed up to 10 years old.

Open access

G. S. Cobb and G. J. Keever

Abstract

Dwarf Japanese euonymus (Euonymus japonica Thunb. ‘Microphylla’) and Japanese holly (Ilex crenata Thunb. ‘Compacta’), grown in fresh or aged (1 year) pine bark amended with a slow-release complete fertilizer, were supplied with NH4NO3 weekly at 0, 100, 200, or 300 ppm N. Plant growth, foliar color, leaf tissue N, and leachate soluble salts increased with increasing levels of supplemental N while tissue K, Ca, and Mg decreased. Plant growth, foliar color, and leaf tissue N, P, Ca, and Mg in fresh pine bark equaled or exceeded that in aged pine bark at all levels of supplemental N. Leachate soluble salts, pH, and leaf tissue K was higher in aged pine bark.

Open access

R. C. J. Koo and T. W. Young

Abstract

As leaves of ‘Tonnage’ avocado (Persea americana Mill.) increased in age, N, P, and K contents decreased, while Ca, Mg, Mn, Cu, Zn, and Fe contents were higher. A comparison of leaves from 1st and 2nd flushes showed similar trends reflected in leaf age. The basal leaf was lower in P but higher in Ca, Mg, and Cu when compared with the terminal leaf of the same twig. Only N and Cu contents were different when leaves from fruiting and nonfruiting twigs were compared. Practical application of the data in sampling avocado leaves is discussed.

Open access

R. A. Reinert and W. R. Henderson

Abstract

Six cultures of Lycopersicon esculentum Mill. were exposed to 3 doses of ozone (O3) at 3 ages. Cultivars exposed to O3 at 2 weeks age ranked differently in sensitivity based on foliar injury than cultivars exposed at 4 and 6 weeks. Cultivars were more sensitive to O3 at 4 than at 6 weeks but sensitivity rankings based on foliar injury were similar. The highest O3 dose significantly inhibited the growth of all cultivars, except ‘Heinz 1439’ at 6 weeks. Cultivar rankings based on average percent change in growth from control plants were more similar at 4 and 6 weeks compared with 2 weeks.

Open access

Virginia I. Lohr, Sherry Hsiao-lei Wang, and Jeffrey D. Wolt

Abstract

Selected physical and chemical properties of fresh spent mushroom compost were evaluated and compared to the properties of spent mushroom compost which was aged aerobically for 6 weeks. Bulk density, total pore space, total water at saturation, and percentage air space in fresh and aged spent composts were acceptable for plant growth. Both contained very high levels of soluble salts which were readily leachable. Concentrations of metals were acceptable, but concentrations of K, Ca, and Mg could lead to plant nutrient imbalances. Concentrations of NH4-N in fresh spent mushroom compost were high.

Free access

M.E. Garcia, C.R. Rom, and J.B. Murphy

The effects of shading and leaf age on the production of foliar phenolics of two apple (Malus domestica Borkh.) cultivars, `Liberty' and `Red Rome Beauty', were studied. Potted trees were grown outdoors and their leaves tagged weekly when they reached 20 mm in length. This process continued for the duration of the experiment. At 3 weeks from budbreak, the trees were placed in three shade treatments: 0% shade (control), 60% shade, and 90% shade. After 5 weeks, the leaves were collected for phenolic assay. Specific leaf weight (SLW) was determined from the leaf below the tagged leaf. Shade significantly affected the total phenolic content. Leaves in 0% shade had the highest levels of total phenolics. The phenolic content decreased with increasing shade, with trees in 90% shade having a 72% reduction in total phenolics. There was a significant shade by leaf age interaction. There was a decrease in total phenolic content with increasing leaf age except for those leaves whose development occurred before the experiment was started. The 1-week-old leaf had the highest phenolic content, while 4-week-old leaf had the lowest amount. The 5- and 6-week-old leaves that had been tagged prior to the onset of the shade treatments has similar phenolic content in all treatment. SLW significantly decreased with increasing shade and increased with leaf age. Results of this study indicate that light and leaf developmental stage are important factors in the total foliar phenolic content, but, once phenolics are synthesized, shading does not affect their content.

Open access

Edward L. Loomis and Orrin E. Smith

Abstract

Unimbibed seeds of cabbage (Brassica oleracea L. Capitata group, cv. Early Jersey Wakefield, were artificially aged at 40°C in 100% relative humidity for up to 20 days. Aged seed and non-aged seed were imbibed in H20 at 25° in the dark up 0, 1, 4 or 16 hours, after which concentrations of Ca, Mg, Mn, K, and Cl in the whole seed were determined by neutron activation analysis. Concentrations of Ca, Mg, and Mn did not significantly change during the imbibition period for either control or aged seed. However, as the aging time increased, seeds lost increasing amounts of K and Cl during imbibition. The concentration of K decreased continually throughout the imbibition period in both aged seed and control seed. The decrease was significantly greater in the aged seed. Cl, too, was lost during imbibition and like K, the greater loss occurred in aged seed.

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Mary C. Acock, Zhongchun Wang, Basil Acock, and Robert Jones

The U.S. State Dept. annually publishes estimates of narcotic drug crop production worldwide. The areas under cultivation are well known but yields per unit land area are not. Determining opium gum yield from illicitly grown poppy Papaver somniferum L. is difficult and dangerous. Removing plants from the field and harvesting gum in a safe place would allow us to measure gum yield from one short field visit. To interpret these results in terms of total gum yield from the field, one must know how the measured gum is affected by gum collecting method, capsule age, and phenotype. Opium poppy seeds from three phenotypes (purple, white, and red-white flowers) were grown in a greenhouse and plants were either cut at the soil level or left intact for opium gum harvest at 7, 12, and 22 days after flowering (DAF). Capsule firmness was measured to estimate gum yield and capsule age, and the relationship between total gum yield and yield from the first lancing was examined. The average gum yield (8.4 mg·g–1 dry weight capsule) for the purple-flowered phenotypes was 17% and 25% lower than for the white- and red/white-flowered phenotypes, respectively. Capsule firmness of the three phenotypes varied from ≈800 to 2300 N·m–1 as the capsule aged. Gum yield and capsule firmness increased with capsule age but the timing of those changes differed among phenotypes. No significant correlations were found between capsule firmness and gum yield or between capsule firmness and age. Therefore, capsule firmness cannot be used to predict gum yield or capsule age. Gum yield from the first lancing was linearly correlated with total gum yield (r2 = 0.82). Since this relationship changes with growing condition, it is insufficient to predict total gum yield. Gum yield from cut plants was significantly lower than from intact plants for all three phenotypes at 22 DAF and for white-flowered phenotypes at 12 DAF. No difference in gum yield was observed between cut and intact plants at 7 or 12 DAF for purple and red/white-flowered phenotypes. The relationship between gum yield from cut and intact plants was too variable to predict gum yield from intact plants by measuring gum yield from cut plants.

Free access

D.F. Warnock, W.M. Randle, and O.M. Lindstrom Jr.

Proper acclimation of onion (Allium cepa L.) seedlings can enhance winter freeze survival; therefore, the effects of photoperiod-temperature combinations, photoperiod, and plant age on the cold hardiness of short-day onions were investigated. Following acclimation at various photoperiod-temperature regimes, different-aged plants were frozen to various subzero temperatures in an ethylene glycol bath and evaluated for cold hardiness. Older plants were more cold hardy than younger plants. An 11-hour photoperiod-decreasing temperature (20/15 to 10/5C day/night) treatment improved plant cold hardiness over other photoperiod-temperature regimes. Various photoperiods (8-, 11-, 14-, and 24-hour) applied during a 14-day, 3C acclimation treatment before freezing had little effect on plant cold hardiness. However, day 7 foliar and day 14 root evaluations indicated that 81-day-old plants given an 8- or 11-hour photoperiod during the 3C acclimation treatment were less cold hardy than older plants (91 or 112 days) given the same acclimation photoperiod.