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  • Author or Editor: J. Arnold x
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In short-term experiments (10 days), urea applied foliarly as the sole N source promoted growth of `T-5' tomato (Lycopersicon esculentum Mill.) seedlings. The optimum urea concentration in the spray solution was 0.2% (w/w), and the best application frequency was once a day. Higher urea concentrations suppressed growth, producing severe leaf damage. The growth observed with foliar urea was less than that observed when inorganic N was supplied to the nutrient solution. Tomato seedlings absorbed 75% of the foliar applied urea within 12 hours and 99% within 24 hours after application. Urea concentrations in the plant tissues increased rapidly after foliar application. The maximum concentration was obtained in shoots at 12 hours and in roots at 24 hours after application. After that, concentration in the tissue declined to its original value within 48 hours. Tissue ammonium concentrations also increased after foliar application of urea. Shoot and root ammonium concentrations reached a maximum after 12 hours and stayed constant for the remainder of the 48-hour observation period. In the long-term experiment (5 weeks), the growth obtained with daily foliar applications of urea as the sole N source was only 10% of that when mineral N was available in the nutrient solution. Ammonium concentrations in the tissues of urea-treated plants were higher than those of plants treated with mineral N in the nutrient solution. Although urea concentrations were initially higher in plants treated with mineral N, after 2 weeks urea concentrations declined in these plants and increased in the shoots of plants receiving foliar applications of urea. These results indicate 1) that urea applied foliarly can supply at least part of the N required to sustain growth; 2) that urea is absorbed and assimilated fast enough to alleviate N deprivation; and 3) that failure to promote rapid growth with foliar urea is probably due to phytotoxicity and not to N deprivation.

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Concentrations of up to 1.0 μm NiCl2 in a nutrient solution improved growth of tomato (Lycopersicon esculentum Mill. `T-5') seedlings that received foliar urea as their sole nitrogen source. Nickel in the nutrient solution decreased the amount of urea present in the shoots and increased the amount in the roots, although it had no significant effect upon leaf urease activity. These results indicate that a) the presence of nickel in the nutrient solution improves growth of plants receiving foliar urea and b) the effect of nickel was related more to increased urea translocation from shoot to root than to enhanced leaf urease activity.

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We examined root ammonium absorption by tomato seedlings (Lycopersicon esculentum Mill. `T-5') after first exposure of the roots to ammonium. Some plants received a nutrient medium containing nitrate as the sole N source. In a second treatment, the leaves were sprayed daily with a urea solution, while the roots were in N-free medium. The last two treatments were initially grown in medium that contained ammonium nitrate, but then either were shifted to a N-free medium for 10 days or had their roots excised and were rerooted in N-free medium for 21 days. Root ammonium absorption remained constant after first exposure to ammonium for the plants exposed to nitrate alone, whereas root ammonium absorption declined with time for the other three treatments. These results indicate that for tomato a) ammonium in the rhizosphere does not induce root ammonium absorption and b) some product of ammonium metabolism represses root ammonium absorption.

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Zea mays L. and Taxodium distichum L. seedlings were grown for 35 days in sand or 3:1 milled pine bark:sand media in 0.7 liter containers. Containers were painted on interior surfaces with 100 g Cu(OH)2/liter or 200 g Cu(OH)2/liter latex carrier (Spin Out™) or not. Five seedlings of each treatment combination were watered daily from 9.5 liter reservoirs with 100 ml of recycled fertilizer (20N-8.7P -16.6K. pH 6.0) solution initially containing 0.036 mg Cu/liter. Fertilizer solutions containing 0.036, 5, 10, 100, or 1000 mg Cu/liter were used to develop toxicity response curves with additional seedlings. Growth of both species in both media was increased by Spin Out treatments. Soluble Cu content of the recycled solution from Spin Out treated containers increased slightly (<1.2 mg/liter) during the experiment. Soluble Cu in leachate from Cu-treated containers ranged from 0.2 to 5 mg/liter with sand and from 0.30 to 1.2 mg/liter with bark. Soluble Cu in leachatc from non-treated containers ranged from 0.02 to 0.40 mg/liter with sand and 0.10 to 0.86 mg/liter for bark media.

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Ninety seedlings from each of seven half-sib families of sycamore (Platanus occidentalis L.) were grown to marketable size in 9.1-liter containers in College Station, Texas. Dry matter partitioning was assessed with 10 seedlings each of four half-sib families grown in 4.7-liter containers. Half-sib families included selections native to Brazos County, Texas, and Putnam County, Tenn., and four half-sib families from the Westvaco Corp. (WV) or Texas Forest Service (TFS) tree improvement programs. Families could be separated into three groups with TFS-09 attaining a significantly greater height than other families, while Brazos-D, Brazos-C, and TFS-24 were intermediate and WV-10 and WV-14 were shortest. Contrary to previous field production studies, a weak inverse correlation (R 2 = –0.19, P > 0.01) was observed between the number of cuts required to remove multiple leaders and plant height, perhaps due to episodic shoot elongation in south Texas conditions vs. a single flush in northern regions. Corrective pruning removed more dry matter from TFS-09 than from Brazos-D, Brazos-C, and Putnam seedlings. Total dry weights of TFS-09 and Brazos-C were greater than WV-14 or Putnam seedlings.

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Seven half-sib families of Platanus occidentalis L., either genetically improved selections (TFS-09, TFS-24, WV-10, WV-14) or non-improved selections (Brazos-C, Brazos-D, Putnam), were grown outdoors in 2.3-L to 9.1-L containers, then transplanted in fall, spring, or summer to assess root regeneration potential (RRP) and initial (2 year) post-transplant landscape growth. TFS-09, TFS-24, Brazos-C, and Brazos-D were Texas selections, while WV-10, WV-14, and Putnam were from Tennessee and Kentucky. Generally, local half-sib families grew more rapidly than geographically distant families and some genetically improved selections grew more rapidly than non-improved selections, both in the landscape and nursery. Rapid growth of new roots and transplanted root dry matter were more consistently associated with successful transplant establishment across families than other measures of RRP. Survival was reduced after summer vs. spring or fall transplant.

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Abstract

Vegetative and fruiting responses of peach [Prunus persica (L.) Batsch cv. June Gold] treated 3 years with glyphosate [N-(phosophonemethyl)glycine], applied at 2.2 and 4.4 kg/ha singly or in combination with 2.2 kg ai/ha simazine [2-chloro-4,6-bis(ethylamino)-s-triazine] or oryzalin [3,5-dinitro-N4,N4-dipropylsulfanilamide], and a treatment of 0.6 kg ai/ha paraquat (1-1’-dimethyl-4,4’-bipyridinium ion) plus simazine or oryzalin were compared to trees in a hand cultivated control. Herbicide treatments resulted in increased trunk diameters and fruit set while glyphosate combinations resulted in improved yields.

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Abstract

Naphthaleneacetic acid (NAA) ethyl ester formulation at 0.25% plus 20% flat white latex paint applied to nonbearing peach [Prunus persica (L.) Batsch] tree trunks reduce sprouting, had no effect on tree growth, and did not induce gummosis.

Open Access

A single sprinkler line-source was used to provide irrigation treatments to three tomato (Lycopersicon escu Mill.) varieties (`Baja', `Rowpac', and `Roza') during 1988 and 1989 in northwestern New Mexico. In both years, marketable fruit yield (Y) of all varieties increased linearly with increased irrigation (1). However, the regression coefficients describing the Y vs. I relationship differed with variety and year. In 1989, `Rowpac' Y ranged from 40.3 to 114.2 Mg ha-1 at levels of 31.5 and 62.5 cm, respectively. Yields of `Baja' and `Roza', while similar to those of `Rowpac' at low I levels, were 59% and 71% of `Rowpac' Y, respectively, at the highest level of irrigation. At any given I level, Y was lower in 1988 than in 1989. While average weight per fruit (wt/fruit) and number of fruit per plant (no/plant) increased with increasing I level in all varieties, increased Y in `Rowpac' had a higher positive correlation with no/plant (40 to 90) than with wt/fruit (85 to 120 g). Increasing Y in `Baja' on the other hand, correlated much better with increased wt/plant (100 to 195 g) than no/plant (20 to 45).

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Leaves of chilled `Moss-Agate' Episcia (Mart.) plants exhibited direct chilling injury (i.e., watersoaked browning of leaf blade interveinal areas within 24 h of exposure to low temperature) immediately following exposure in darkness to 10C for 0.5 or 1.0 h. Chlorophyll fluorescence peak: initial ratios and terminal: peak ratios of chilled Episcia were -reduced 20% and 25%, respectively, 3 h after chilling, a result suggesting possible photosystem II damage. Total leaf chlorophyll content was reduced by 17% within 3 h of chilling and CO2uptake also was reduced at this time. Leaves of chilled `Rudolph Roehrs' Dieffenbachia maculata (Lodd.) (D. Roehrsii Hort.) plants expressed no visible injury within 24 h of 1.2C chilling in darkness for 36,48, or 60 h, but CO2uptake was reduced by 70% compared to the control 3 h after chilling. Visible injury began to appear 27 h after chilling, and the older leaf blades of all chilled plants exhibited a watersoaked appearance 75 h after chilling. Chlorophyll fluorescence peak: initial ratios of chilled Dieffenbachia did not vary, and terminal: peak ratios were not reduced until 147 h after chilling, when the injured tissue was extremely flaccid and translucent. Chilling reduced the chlorophyll content of Dieffenbachia by 10% in some plants 27 h after chilling and by 35%. in all plants 75 h after chilling. Transpiration rate was reduced and stomata] diffusive resistance increased 27 h after chilling.

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