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  • Author or Editor: Chris A. Martin x
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Growth and topological indices of `Eureka' lemon were measured after 6 months in well-watered and well-fertilized conditions and factorial combinations of moderate (29/21C day/night) or high (42/32C day/night) temperatures and ambient (350 to 380 μmol·mol) or elevated (constant 680 μmol·mol-1) CO2. In high temperatures, plants were smaller and had higher levels of leaf chlorophyll a than in moderate temperatures. Moreover, plants in high temperatures and elevated CO2 had about 15 % higher levels of leaf chlorophyll a than those in high temperatures and ambient CO2. In high temperatures, plant growth in elevated CO2 was about 87% more than in ambient CO2. Thus, high CO2 reduced the negative effect of high temperature on shoot growth. In moderate temperatures, plant growth in elevated CO2 was only about 21% more than in ambient CO2. Irrespective of temperature treatments, shoot branch architecture in elevated CO2 was more hierarchical than those in ambient CO2. Specific shoot extension, a topological measure of branch frequency, was not affected by elevated CO2 in moderate temperatures, but was increased by elevated CO2 enrichment in high temperatures-an indication of decreased branch frequency and increased apical dominance. In moderate temperatures, plants in elevated CO2 had fibrous root branch patterns that were less hierarchical than at ambient CO2. The lengths of exterior and interior fibrous roots between branch points and the length of second-degree adventitious lateral branches were increased >50% by high temperatures compared with moderate temperatures. Root length between branch points was not affected by CO2 levels.

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Seedlings of Carica papaya L. `Waimanalo' (papaya) were transplanted into 27-L containers filled with nonsterile composted landscape yard trimmings passed through a 1.3-cm screen. At transplanting, papaya plants were inoculated with either one of three different AMF communities or were not inoculated as control plants. Two of the AMF communities were from Arizona citrus orchards, and one AMF community was from an undisturbed western Chihuahuan Desert soil. After transplanting, papaya plants were grown for 4 months under well-watered conditions in a temperature-controlled (32 °C day/24 °C night) glasshouse (45% light exclusion). Control plants remained non-mycorrhizal. Total colonization of papaya roots by AMF communities ranged from 56% to 94%. Depending on mycorrhizal treatment, AMF arbuscules and internal hyphae were present in 30% to 60% and 20% to 24% of roots, respectively. Noticeably absent in papaya roots were AMF vesicles. Papaya height, trunk diameter, and leaf phosphorus concentration were similar for inoculated and control plants. Compared with control plants, papayas inoculated with AMF communities had about 20% less shoot dry weight and about 50% less root dry weight. Under nonlimiting conditions in an organic substrate, AMF communities did not stimulate papaya growth but rather appeared to function as a carbon sink.

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Paclobutrazol at 0 and 750 μl·liter–1 was sprayed on shoots of Feijoa sellowiana O. Berg. and Ligustrum japonicum Thunb. grown under similar production regimes in central Arizona (subtropical desert) and southern Georgia (humid temperate). Five months after application, Feijoa and Ligustrum leaves were generally smaller and thicker in Arizona than in Georgia. Arizona leaves were thicker than those in Georgia because of more layers of palisade and spongy mesophyll cells. Compared with leaves from control plants, paclobutrazol 1) increased Feijoa leaf area in Georgia, 2) decreased Ligustrum leaf area at both locations by ≈50%, and 3) decreased leaf thickness of both species in Arizona. Arizona Feijoa leaves had trichomes on adaxial and abaxial surfaces, whereas Georgia Feijoa leaves had trichomes on abaxial surfaces only. Paclobutrazol increased trichome frequency on adaxial surfaces of Arizona Feijoa leaves. Stomatal frequency of Georgia Feijoa leaves was about doubled by paclobutrazol. Reflectance of near-infrared radiation by paclobutrazol-treated Feijoa leaves was 1.4 times higher than that of nontreated leaves in Georgia and 1.9 times in Arizona. Near-infrared reflectance by Georgia Ligustrum leaves was 1.3 times higher than by Arizona Ligustrum leaves and was not affected by paclobutrazol. Leaf reflectance of photosynthetically active radiation (PAR) by Arizona Feijoa was higher than by Georgia Feijoa. Paclobutrazol increased PAR reflectance by Arizona Feijoa leaves. In contrast, Georgia Feijoa PAR reflectance was decreased by paclobutrazol. Paclobutrazol or location did not affect Ligustrum PAR reflectance. Chemical name used: (2RS,3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)pentan-3-ol (paclobutrazol).

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Hydration and elemental absorption of two commercially-available polyacrylamide gels (A and B) were studied in response to a 24-hr soak time in Hoagland's solution concentrations of either 2X, 1X, 0.5X, 0.25X, 0.125X or 0X (deionized water). Elemental absorption of gel specimens was observed and analyzed within the gel matrix on a Philips CM12S STEM equipped with an EDAX 9800 plus EDS unit for micro x-ray analysis. Thick sections were cut on dry glass knives using an RMC MT6000 ultramicrotome. Surface analysis of bulk specimens was made with an AMR 1000A SEM plus PGT1000 EDS unit. Overall, gel hydration decreased quadratically as solution concentration increased linearly; however, hydration for gel A was generally greater than for gel B. Surface analysis of gel samples revealed the presence Ca, K, P, S, Fe, and Zn for both gels. An analysis within the matrix of gel B revealed the presence of Ca, K, P, S, Fe, and Zn; however, an analysis within the matrix of gel A revealed the presence of Zn, and Fe only. The increased absorptive capacity of gel A appeared to be coupled to reduced migration of salts into the gel matrix.

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In the United States, urban population growth, improved living standards, limited development of new water supplies, and dwindling current water supplies are causing the demand for treated municipal water to exceed the supply. Although water used to irrigate the residential urban landscape will vary according to factors such as landscape type, management practices, and region, landscape irrigation can vary from 40% to 70% of household use of water. So, the efficient use of irrigation water in urban landscapes must be the primary focus of water conservation. In addition, plants in a typical residential landscape often are given more water than is required to maintain ecosystem services such as carbon regulation, climate control, and preservation of aesthetic appearance. This implies that improvements in the efficiency of landscape irrigation will yield significant water savings. Urban areas across the United States face different water supply and demand issues and a range of factors will affect how water is used in the urban landscape. The purpose of this review is to summarize how irrigation and water application technologies; landscape design and management strategies; the relationship among people, plants, and the urban landscape; the reuse of water resources; economic and noneconomic incentives; and policy and ordinances impact the efficient use of water in the urban landscape.

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