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.
Chris A. Martin, John M. Ruter, Robert W. Roberson and William P. Sharp
Chris A. Martin, William P. Sharp, John M. Ruter and Richard L. Garcia
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).