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Open access

L. E. Scott and John C. Bouwkamp

Abstract

Four cultivars of sweet potatoes (Ipomoea batatas Lam.) were sampled bi-weekly during the period of storage root development Although the root weight increased nearly 8-fold during the sampling period there was only a 35% increase in the number of roots. Alcohol insoluble solids (AIS) and % dry matter generally showed a slight increase throughout the season and specific gravity a slight decrease. Total sugars and reducing sugars failed to show a trend. In contrast, the processed roots tended to become softer as the season progressed. Firmness was related to chronological age of roots rather than harvest date. The later the planting the higher were total and reducing sugars but planting date had no consistent effect on other raw product attributes.

Open access

Yi-Chi Hsieh and John Sacalis

Abstract

Studies were conducted to determine the involvement of ACC movement from extrapetal portions with initiation of petal senescence. During early senescence, ACC in all portions except the calyx displayed transient increases in levels of ACC. The largest increase in ACC specific concentration occurred in the receptacle. Removal of petals at harvest resulted in accumulation of ACC in the ovary and receptacle. [14C]ACC applied to the styles moved to the petals within 24 hr, but during this time, very little 14C was found in the receptacle. Although the major rise in ACC occurred in styles, ovary, receptacle, and petals between days 6 and 10 of aging, a secondary transient peak of ACC was always observed between days 2 and 4 only in the receptacle. It is suggested that the receptacle may contribute significantly to the initiation of petal senescence by acting as a source of ACC. Chemical names used: 1-aminocyclopropane-1-carboxylic acid (ACC).

Free access

Mark D. Sherratt, Donna V. Coffindaffer-Ballard, and Bradford C. Bearce

Four poinsettia cultivars were planted in root media containing 0%, 25%, or 50% (by volume) of coal bottom ash or aged hardwood sawdust. Bract color development in `Supjibi' was delayed in media containing sawdust or ash by up to 8–12 days. Bract color initiation of `Jingle Bells' and `Success' occurred earliest in media containing 25% sawdust, but color development was delayed in 50% coal ash. Color development in `Dark Red Hegg' was not affected by ash or sawdust. Analysis of combined leaves from all four cultivars showed Fe levels below normal where media contained sawdust. Leaf Mo concentrations increased with increased media sawdust to above the normal range, but Mn levels were below the normal range in sawdust media. Leaf Ca levels were below normal in all media, possibly due to excessively high K levels in media and leaves. When fertilizer concentration and frequency were adjusted to media EC levels, control media (0% ash or sawdust) required 100 ppm N once a week. Media containing sawdust required 300 ppm to maintain EC levels between 1.25–2.25 dS·m–1 and coal ash media were irrigated with water following the sixth week after planting due to EC levels >2.25.

Free access

M.H. Dickson and R. Petzoldt

Resistance to downy mildew [Peronospora parasitica (pers.) ex. Fr.] in broccoli (Brassica oleracea L. Italica Group) depends on plant age. Seedling resistance seems to be independent of mature-plant resistance, where a mature plant is defined as having eight or more leaves. Our results suggest that, by using mature-plant resistance, an almost continuous variation instable levels of mature-plant resistance can be developed. Similarities in the response of mature plants of various lines to isolates from California, Washington, New York, and South Carolina indicated that the predominant race was the same at all locations. Correlations between resistant and susceptible responses to isolates from California, Washington, New York, and South Carolina varied from r = 0.48 to 0.74 depending on isolate source. The results indicated that selecting for high levels of resistance in mature plants at one location should result in good resistance elsewhere in the United States. Selecting immature plants (three to six leaves) may provide less reliable results due to the transitional status of the plant; i.e., between seedling and mature plant.

Free access

Jordi Canals, Jorge Pinochet, and Antonio Felipe

The influence of temperature and age of the plant was determined on nematode reproduction on a susceptible almond (Prunus amygdalus Batsch.) and on a resistant peach-almond hybrid (P. persica Stok. × P. amygdalus Batsch.) rootstock inoculated with Meloidogyne javanica (Treub) Chitwood. Experiments were conducted under greenhouse conditions in heated and unheated sand beds. `Garrigues' almond inoculated with 3000 nematodes per plant showed extensive galling, high final nematode population levels, and high counts of nematodes per gram of root at 27 and 32C. The hybrid G × N No. 1 showed minimal galling and reproduction at 27C but higher levels of galling and final population and nematode counts per gram of root at 32C, suggesting a partial loss of resistance with temperature increase. One-month-old and 1-year-old plants of `Garrigues' were susceptible following inoculation with 2000 nematodes per plant, although plantlets (l-month) were significantly more affected. Plantlets of hybrid G × N No. 1 were also susceptible, but 1-year-old plants were resistant. Resistant genotypes (G × N selections) seem to require root tissue maturation before expressing full resistance.

Open access

Richard J. McAvoy and Harry W. Janes

Abstract

Tomato plants (Lycopersicon esculentum Mill. cv. Laura), pruned to a single-flower truss, were exposed to 90 μmol·s−1·m−2 supplemental photosynthetic lighting (0400 to 2200 hr) during the developmental period: a) anthesis to initial fruit set, b) anthesis to mature-green fruit, or c) anthesis to red-ripe fruit. The yield response was compared to plants receiving d) no supplemental photosynthetic lighting after incipient anthesis. The greatest increase in average fruit weight was produced with continued supplemental lighting during the developmental-period initial fruit set to the mature-green stage. Net photosynthetic activity, μmol CO2/min per dm2, was the greatest in the canopy during early anthesis and then steadily declined as the canopy aged. Net whole plant photosynthetic activity, μmol CO2/min per plant, increased steadily after the early anthesis stage of development to a peak rate during the rapid fruit development stage. Net whole plant photosynthetic activity then declined as the plant approached the mature-green and then finally the red-ripe stage of fruit development.

Free access

Jaimin S. Patel, Shouan Zhang, and Maria I. Costa de Novaes

severity of basil downy mildew is strongly associated with the age of the plant, environmental conditions, and cultivar susceptibility. Cool, wet, and humid weather, which are characteristics of the climate of Florida, favor infection by P. belbahrii , and

Free access

Wei Qiang Yang*

In a 2-year study, the decomposition rates (changes in carbon to nitrogen ratio) of two kinds of sawdust used for blueberry production were determined. The effects of sawdust age and nitrogen application rates on carbon to nitrogen ratio (C:N ratio) of two sawdust types were evaluated. When nitrogen was not applied, the C:N ratio in fresh and aged sawdust decreased 30% and 10% respectively over a 1-year period, indicating fresh sawdust decomposed faster than aged sawdust when used as a surface mulch. However, the C:N ratios between soils amended with aged and fresh sawdust were similar when no nitrogen was added, suggesting the age of sawdust does not affect the decomposition rate once the sawdust is incorporated into the soil. It was found that two nitrogen application rates (150 kg·ha-1 vs. 50 kg·ha-1) had an equal affect on the C:N ratio of both sawdust types. Nitrogen application had no affect on the C:N ratio of both sawdust types when both sawdust were used as soil amendments. Clearly, the decomposition rates of the sawdust were influenced by sawdust age and nitrogen application rates.

Free access

George H. Timm and Loretta J. Mikitzel

The influence of paclobutrazol, an inhibitor of GA synthesis, on kindertuber formation was studied using 13.5-month-old `Russet Burbank' potato (Solanum tuberosum) tubers. Suberized apical and distal tuber pieces of equal weight were sprayed daily with distilled water (control), 0.001 and 0.01 mg paclobutrazol/liter with or without 2.5 mg kinetin/liter, and 2.5 mg kinetin/liter alone. The tuber pieces were held in the dark (20C) and harvested 8, 16, and 22 days after the first treatment. Only sprouts developed from control apical piece eyes after 22 days. There was an average of 3.6 sprouts/eye, which, in total, weighed 735 mg. Sprouts (2.4/eye) from treated apical piece eyes averaged 46 mg. By 22 days, 0.001 mg paclobutrazol/liter plus kinetin applied to apical pieces resulted in the most kindertubers, 1.9/eye. The largest kindertubers (1.2 g) were produced from apical pieces treated with 0.001 mg paclobutrazol/liter. At each harvest and regardless of treatment, distal tuber pieces produced larger sprouts and more sprouts per eye than apical pieces. Kindertubers developed from distal piece eyes only with the paclobutrazol plus kinetin treatments. Distal eyes produced half as many kindertubers as apical eyes treated similarly. Apical pieces treated with kinetin alone produced fewer sprouts than control pieces, and fewer tubers than paclobutrazol-treated pieces. Sprout weight per eye of kinetin-treated apical pieces was one-third that produced by control pieces and 5.1-fold greater than that of paclobutrazol-treated pieces. A similar trend was observed with sprout weight from distal eyes. Results suggest lowered GA levels are involved in kindertuber formation on aged potato tubers, and GA content or metabolism of distal pieces is unlike that of apical pieces. Distal tuber pieces do not form kindertubers as readily as apical pieces.

Free access

Jules Janick, Marie Christine Daunay, and Harry Paris

the late Middle Ages, known as the Tacuinum Sanitatis , that provides information on the interrelationship of horticulture and health ( Daunay et al., 2009 ; Janick et al., 2009 ; Paris et al., 2009 ). We further compare modern and medieval feelings