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  • Author or Editor: Charles R. Johnson x
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The influence of N and K rates in Hoagland's nutrient solution on Jalapeño pepper (Capsicum annuum L.) plant growth and pod production was determined on greenhouse-grown plants in sand culture. Varying the rates of N (1 to 30 mm) and K (1 to 12 mm) in Hoagland's solution identified optimum concentrations for Jalapeño plant growth and pod production. Two experiments were conducted to determine Jalapeño pepper sensitivity to differential fertilization. In the experiment seeded in April, nutrient treatments began at transplanting, and in the one seeded in May, treatments began after all plants had flower buds and half had flowered. Biomass and pod production per plant responded curvilinearly to N rate in both experiments. Optimum N rate for pod yield was 15 mm. Nitrogen rate affected pungency of pods only in the first experiment, with 1 mm N reducing capsaicin levels in fruit compared to other N rates. Biomass, fruit count, and fruit weight per plant increased linearly with increasing K rate in the first experiment and curvilinearly with K rate in the second experiment. The optimum K rate for pod yield was 6 mm. Potassium rates did not affect pod pungency. Jalapeño peppers grown in sand culture required 15 mm N and at least 3 mm K for optimum pod production.

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Abstract

Root systems of Pittosporum tobira Thunb. plants were exposed to temperatures of 27°, 30°, or 40°C for 6 hours daily for 7 months. Top and root growth, root carbohydrate levels and photosynthetic rates were reduced by the 40° treatment. Content of K, Fe, and Zn in leaf tissues were reduced at highest root temperatures, while N content showed the opposite response.

Open Access

Abstract

Moderate and severe water-stress, as determined by decreases in stomatal conductance, resulted in significant reduction of leaf area and plant weight in 1-year-old containerized ‘Bluegem’ rabbiteye blueberry. Drought-tolerance appeared to be intermediate to other plant species based on a number of physiological factors. Critical water potential for stomatal closure was −2.2 MPa, transpiration ratio averaged 222 g of water transpired per g dry matter produced and relative water content changed 6.4% per 1.0 MPa change in water potential.

Open Access

Abstract

To determine the potential for root branching, the primary root of Zamia floridana L. seedlings was excised near the root–shoot junction and the cut ends were dipped in 2000 ppm IBA, 2000 ppm BA, or combination of the two, each for 5 sec. Whereas excised control plants produced only one root, those treated with IBA, BA, and IBA–BA averaged 2.1, 3.2, and 2.3 roots, respectively. In all instances, the number of secondary roots increased significantly compared with intact seedlings. Since seedling roots are diarch throughout, new primordia must be initiated in the interfascicular parenchyma tissue for more than two roots to be produced. Treatment with IBA probably disrupted apical control of roots by the shoot meristem and stimulated development of the two possible secondary roots associated with xylem poles, while BA caused new primordia to be formed in the interfascicular parenchyma region. Chemical names used: 1H-indole-3-butyric acid (IBA); N-(phenylmethyl)-1H-purin-6-amine (BA).

Open Access

Six irrigation strategies were imposed on a block of O'Henry peach trees irrigated by fanjets. Treatments received different percentages of ET during the various stages of fruit growth and postharvest. ET was estimated by a large weighing lysimeter containing 2 trees and located in the center of the block. Fruit diameters were measured weekly and final fruit weights were determined at harvest. Adjusted fruit weights were estimated by statistically adjusting each treatment to the same fruit load.

Adjusted fruit weight correlated well with soil water content during the month before harvest but not during early stages of fruit growth. Treatments which applied 50% ET during early stages of fruit growth showed reduced fruit size at that time. However, with applications of 150% ET during the final fruit growth stage, fruit size recovered. Adjusted fruit weight also correlated with measures of tree water status including midday leaf water potential and canopy temperature.

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Abstract

Pittosporum tobira plants were inoculated with the vesicular-arbuscular mycorrhizal (VAM) fungus Glomus mosseae or provided with an inoculum filtrate (nonVAM) and fertilized with 1 of 5 NH4+ /NO3 ratios. Colonized plants had more branching, greater fresh weight, and higher visual grades than nonVAM plants, especially when grown at 50%–75% NO3 -N. Colonized plants also had higher concentrations of transport amino acids in xylem sap compared to nonVAM plants. Results suggest that colonization by Glomus mosseae may affect N metabolism in P. tobira.

Open Access

Abstract

Semi-hardwood cuttings of Ligustrum japonicum Thunb. and Juniperus conferta Pari, were propagated in sand or sand-peat (1:1 volume/volume and top-dressed with 18-6-12 or 14-14-14 Osmocote (18N—2.6P—10.OK and 14N—6.OP—16.6K, respectively). Percent rooting was improved by Osmocote after 8 weeks although all L. japonicum cuttings were rooted after 12 weeks. Fresh weight of roots and dry weight of tops were improved by Osmocote treatment. N and P levels of leaf tissue increased with Osmocote top dressing compared to unfertilized controls. Percent rooting was initially superior in sand but after 10 weeks all cuttings were rooted and root development was greater in sand-peat.

Open Access

Field tests at two locations examined the influence of length and spacing of root propagules on blackberry plant establishment. Root propagules 10.2 cm long spaced 61 cm resulted in greater emergence, plant stand, and shoot growth than 5 cm and 2.5 cm root propagules. Differences in emergence and shoot growth between 10.2 cm progagules spaced 61 cm and 5 cm propagules spaced 61 cm were non-significant. Greenhouse tests compared four lengths of root propagules (15.2 cm, 10.2 cm, 5cm, 2.5 cm) for production of nursery plants. Percent emergence, time of emergence, and number of shoots per propagule produced from 2.5 cm propagules were comparable to results from 15.2 cm and 10.2 cm propagules.

Free access

The heat balance method was used to estimate transpirational sap flow through 60- to 75-mm-diameter stems (trunks) of 3-year-old peach [Prunus persica (L.) Batsch. cv. O'Henry] trees under field conditions. On rare occasions, heat balance estimates agreed well with independent lysimetric measurements, but on most occasions, heat balance estimates of sap flow were unrealistic in both direction and magnitude. In some cases, the errors in sap flow approached two orders of magnitude and were always the result of a calculation involving division by a very small and sometimes negative temperature differential between the stem surface temperature above and below the gauge heater. The occurrence of negative temperature differentials under positive transpiration conditions may be inconsistent with a fundamental assumption in the heat balance model, namely that temperature differentials are solely a consequence of the dissipation of energy supplied to the gauge heater. In the absence of heating power applied to the gauge, temperature differentials exceeding - 1C were correlated with the rate of change in stem temperature, indicating that ambient conditions themselves can impose a bias in gauge signals and, hence, influence gauge accuracy. Our results suggest that the effect of ambient conditions on gauge signals should be critically evaluated before considering heat balance estimates of sap flow as reliable under any given conditions.

Free access

Abstract

A production function was estimated for Ligustrum japonicum L. A medium comprised of 1 peatmoss: 2 sand: 2 pinebark with 10.8 g of fertilizer and 19.3 liters of water per container provides for the least cost production of a “salable” 70 g (dry weight) plant. The method is outlined for determining economic optimality for salable production.

Open Access