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- Author or Editor: F.T. Davies Jr. x
Abstract
A digital automated irrigation-syringe system (DAIS) that monitors environmental conditions for efficient plant cooling and water usage is described. The device consists of a short-cycle syringe irrigation control (intermittent irrigation) for reducing heat load and a long time cycle control for applying larger volumes of water during predetermined irrigation cycles. The syringe (intermittent irrigation) control is operated by selecting threshold levels based on soil and air temperatures and soil moisture. The longer time cycle control is based on a 24-hr cycle that provides regular cyclic irrigation adjusted for daily irrigation number(s) and time length of each irrigation. The DAIS can be used in nursery container and greenhouse production and can be applied to modeling of growth at different water regimes to determine water requirements for optimum crop growth.
Abstract
Crape myrtle (Lagerstroemia indica L. ‘Near East’) explants of 2 nodes were cultured on woody plant medium (WPM) supplemented with PBA, BA, or kinetin. PBA was most effective in promoting axillary shoot proliferation. Maximum number of axillary budbreaks occurred on modified WPM containing 3-9 μm PBA. Subcultured shoots ≥2 cm in length rooted in medium without auxin, and ex vitro rooting and acclimization was also obtained. Chemical names used: 1H-indole-3-butanoic acid (IBA); N-(phenylmethyl)-9-(tetrahydro-2H-pyran-2-yl)-9H-purin-6-amine (PBA), N- (phenylmethyl)-1H-purin-6-amine (BA); N-(2-furanylmethyl)-1H-purin-6-amine (kinetin).
Abstract
The design for a chamber to control high root-zone temperature is presented. Air within the insulated chamber was heated with vinyl-jacketed heating cables and cooled with 1:1 water and antifreeze (v/v) pumped through copper coils. Control of the soil temperature was based upon air temperature around the soil containers within the sealed chambers. Chamber operating temperatures could be held between 20° and 50°C ± 0.2° SE.
Pinus taeda L. seedlings inoculated with the ectomycorrhizal fungus, Pisolithus tinctorius, were grown in a glasshouse for eight months, and then subjected to rapidly developing cyclic water deficits, or to a single slowly developing water deficit. Water deficits developed at a rate of -0.16 MPa per day (predawn total water potential) for five cyclic water deficits, and at -0.04 MPa per day for the slow water deficit. In unstressed seedlings, carbon exchange rates (CER) did not differ between noninoculated and inoculated seedlings. During slow water deficit development, CER steadily declined. During rapid water deficit development, CER remained unchanged, then declined rapidly when water potentials fell below -1.3 MPa. Inoculated seedlings had higher CER when water potential was lower than -1.5 MPa.
Pinus taeda L. seedlings inoculated with the ectomycorrhizal fungus, Pisolithus tinctorius, were grown in a glasshouse for eight months, and then subjected to rapidly developing cyclic water deficits, or to a single slowly developing water deficit. Water deficits developed at a rate of -0.16 MPa per day (predawn total water potential) for five cyclic water deficits, and at -0.04 MPa per day for the slow water deficit. In unstressed seedlings, carbon exchange rates (CER) did not differ between noninoculated and inoculated seedlings. During slow water deficit development, CER steadily declined. During rapid water deficit development, CER remained unchanged, then declined rapidly when water potentials fell below -1.3 MPa. Inoculated seedlings had higher CER when water potential was lower than -1.5 MPa.
Abstract
Leaf cuttings of Rieger elatior begonias (Begonia bertini ‘compacti’ × B. socotrana cvs. Aphrodite Cherry Red and Schwabenland Red) were treated with 6-furfurylamino purine (kinetin), 6-benzylamino purine (BA), and 6-(benzylamino)-9-(2-tetrahydropyranyl)-9H-purine (PBA). BA and PBA enhanced bud and shoot regeneration in ‘Aphrodite Cherry Red,’ while kinetin showed no activity. All cytokinins tested reduced shoot development in ‘Schwabenland Red.’ PBA stimulated optimal bud and shoot development when applied to ‘Aphrodite Cherry Red’ leaf cuttings as a 12 hour 15 μM basal-petiole dip, 1000 μM spray, and 0.01% talc-petiole- dip. Cuttings taken from ‘Aphrodite Cherry Red’ stock plants treated with 1000 μM PBA successfully generated new plants.
Abstract
Adventitious root formation was stimulated with foliar application of indolebutyric acid (IBA) from 1000 to 1500 mg/liter for juvenile and 2000 to 3000 mg/liter for mature leaf bud cuttings of Ficus pumila L. IBA increased cambial activity, root initial formation, and primordia differentiation and elongation. IBA stimulated rooting when applied to juvenile cuttings at 3, 5, or 7 days after experiment initiation, but had no effect on mature cuttings when applied at day 15, the final treatment period. The interaction of IBA/gibberellic acid (GA3) did not affect early root development stages, but reduced root elongation and quality once primorida had differentiated. IBA/6-(benzylamino)-9-(2-tetrahydropyranyl)-9H-purine (PBA) inhibited rooting at early initiation stages.
Abstract
High root-zone temperatures can stress container-grown plants and ultimately reduce nursery productivity in the southern United States. Water relations of glasshouse-grown Berberis thunbergii DC ‘Atropurpurea’ Buxus microphylla Seibold and Zucc japonica and Pittosporum tobira, (Thunb.) Ait. ‘Wheeler’ were studied under high-temperature root-stress conditions using container-grown plants that were either colonized with vesicular arbuscular mycorrhizal fungi (VAM) or noncolonized. Predawn xylem water potential in stems (ψstem) increased initially (more positive) in response to high root-zone temperatures (40° to 45°C), and then decreased over a 5-day period. Stomatal conductance (gs) and evapotranspiration (ET) were reduced incrementally over time in response to high root-zone temperatures. Root damage occurred, as indicated by reductions in root quality and gs at 35° and 40° for B. thunbergii and P. tobira, and at 40° and 45° for the more high-temperature-resistant B. microphylla. Colonization increased gs and ET of B. microphylla at ambient (25°) and high temperatures (45°) and increased ET of B. thunbergii at 25°. Colonized plants had lower (more negative) ψshoot with initial exposure to increased root-zone temperatures; however, throughout the remainder of the study period there was little reduction in plant stress with the mycorrhizal isolates used. Root hydraulic conductivity (Lp) increased markedly in B. thunbergii compared to B. microphylla at 40° and 45°, indicating less high-temperature resistance in B. thunbergii roots. Mycorrhizal colonization did not moderate hydraulic conductivity at high root-zone temperatures of 40° and 45°. Of the two species, mycorrhizal B. thunbergii had lower Lp at 25° and B. microphylla had lower Lp at 35°.
One-node explants and one-node stem cuttings of Asian jasmine [Trachelospermum asiaticum (Siebold & Zucc.) Nakai] were rooted, respectively, in vitro [tissue culture (TC)] or by conventional macropropagation (MACRO). The TC and MACRO stem bases were then analyzed for differences in the time-course sequence of 1) root primordia initiation and development and 2) adventitious root xylem development and root-to-shoot xylem connections. Early root primordia were observed at Day 3, and, by Day 7, root-to-shoot xylem connections were equally developed in TC and MACRO systems. Continued development and emergence of adventitious roots were observed at Days 8 to 10. At Days 13 and 18, when viewed using scanning electron microscopy, TC root hairs were morphologically thicker and one-third to one-half the length of MACRO root hairs. There was no apparent difference in root-hair density. Inferior TC root-hair length may be a factor in the acclimation of TC-generated plantlets.
In vitro tissue-cultured (TC) and macropropagated (MACRO) 18-day old adventitious roots of Asian jasmine [Trachelospermum asiaticum (Siebold & Zucc.) Nakai] were compared for their ability to absorb and translocate radiolabelled P from a nutrient solution. Samples were taken at 1, 2, 4, 8, 12, and 24 hours after the initial dosage of the nutrient solution with 7.4 × 10-2 MBq KH 32 2PO4/liter. TC roots were capable of absorbing P, but at significantly lower levels than MACRO roots. Greater P absorption occurred in MACRO roots within the first hour and continued for the duration of the experiment. However, there was no significant difference in the rate of P translocation from roots to shoots between treatments. Root systems formed in vitro survived acclimation and had developed into well-branched root systems after 13 weeks. Reduced P absorption by TC roots did not limit either P translocation or survivability during and after acclimation.