Search Results
Abstract
In vitro propagation of Mammillaria elongata DC plants was successful using tubercle explants grown on a medium based on Murashige and Skoog’s high salts supplemented with various auxins and cytokinins. Optimum callus proliferation occured in response to 2,4-dichlor-ophenoxyacetic acid (2,4-D) (2-10 mg/liter) with either kinetin or 6-(dimethylallylamino)-purine (2iP) (1-2 mg/liter). Root initiation was optimized with either napthaleneacetic acid (NAA) or indolebutyric acid (IBA) (60 mg/liter). Shoot initiation was optimized by addition of 2iP (10 mg/liter) and indoleacetic acid (IAA) (1 mg/liter). The auxin:cytokinin balance required for shoot initiation appears to be unique for each species of Mammillaria studied. Shoots developed in vitro of M. elongata were successfully transferred to greenhouse conditions, where they rooted and continued to grow.
Abstract
Turfgrass wear tests were conducted at Griffin, Ga. in 1985 and 1986 on ‘Tifway’ bermudagrass (Cynodon dactylon × C. transvaalensis) using several golf car tire designs (tread configurations, radial or non-radial), golf cars, and traffic patterns. Wear damage to bermudagrass in all studies was assessed by visual turf quality, color, verdure, and leaf bruising. Golf car traffic caused significant wear damage regardless of golf car, tire design, or traffic pattern. Damage increased with frequency of trips over the site and with moderately sharp turns. Differences in wear injury between the tire designs did occur, but were minor in most instances. These differences could not be explained by tread pattern alone, since similar designs gave different degrees of wear. Whether the tire was radial or not did not influence turfgrass wear. Golf car type exhibited a minor effect on bermudagrass wear. Management alternatives to minimize turfgrass wear should concentrate on distributing traffic and avoiding sharp turns, while selection of pneumatic tire design or golf car is of minor relative importance.
A turfgrass wear injury study was conducted at Griffin, Ga., on `Tifway' bermudagrass (Cynodon dactylon × C. transvaalensis) using two golf car tires and three golf car types driven in a semicircular pattern to deliver 85 passes over the tread path plot area. Wear injury for the 14 days after wear was applied was assessed by visual quality, percent green coverage, leaf bruising, and verdure. Golf tire × car interactions occurred, but more wear occurred with the low pressure (48 × 103 Pa), dimpled tread tire with flexible sidewalls than the commonly used bias ply (4-ply), V-shaped tread tire with more rigid sidewalls. Significant differences in wear damage occurred for golf car type but were influenced by tire design. Thus, selection of golf car tire and golf car type can influence the degree of wear injury on turfgrass sites.
Abstract
Several slow-release nitrogen (N) sources, applied as single spring treatments at 98 kg N/ha, were compared to a single application of water-soluble N in April at 98 kg N/ha or 49 kg N/ha applied in April and repeated in June to evaluate their effect on centipedegrass [Eremochloa ophiuroides (Munro) Hack.] performance. In spring, Escote 100, IBDU (fine, isobutylidene diurea), sulfur-coated urea (SCU) and SCU + AN provided color equal to NH4NO3 (AN), but only treatments containing SCU produced turfgrass quality equal to AN. During the summer, all slow-release N carrier treatments provided turfgrass quality and color that was equal to or better than that provided by AN. Ureaform (UF) resulted in better late fall color than did AN, but fall quality ratings were similar regardless of N source. Thatch accumulation was similar for all treatments and no centipede decline was observed. Leaf N content was not markedly influenced by treatment and no consistent trend in relative growth rate among N sources was apparent. Thus, while no single slow-release N source provided a season-long advantage over AN applied in April, all could be used effectively on centipedegrass.
Abstract
Carnations (Dianthus caryophyllus cv. White Sim) planted August, 1970 were grown under long (LD) or normal (ND) daylengths and 4 continuous soil heating treatments, (none, 18°, 21°, 32°C). The rate of leaf unfolding and flower development was nearly equal for all treatments, although flowers appeared to initiate 3 weeks earlier under LD. Peaks of cut flower production were 1 month earlier and of greater magnitude under LD than ND. High soil temp (21°, 32°) under ND (winter daylengths) delayed peak flower production by another month. Total flower production was significantly greater with the plants grown under LD. Flowers from plants with high soil temp (21°, 32°), particularly those under LD, were of significantly better quality than those at 18° or without supplemental soil heat.
Abstract
Abnormal needle tip curling was induced by low humidity in 4 half-sib families of loblolly pine (Pinus taeda L.) grown in a growth chamber. The injury developed on new growth on both 12-week-old and 1-year old seedlings when plants were maintained under 30% ± 5% relative humidity with a 16-hour photoperiod, 23°C light period and 17° dark period. Very little injury developed on plants maintained at 70% ±5% relative humidity. Significantly more needle tip curling occurred on seedlings grown from seed collected in Texas than in seed collected from Virginia.
Abstract
Spine primordia of Mammillaria elongata are initiated in acropetal sequence, beginning on the abaxial side of the spiniferous meristem that occupies the summit of a young tubercle and continuing along either side until a single whorl is completed. If a central spine occurs, it is the last to be initiated and the first to begin elongation. Elongation of the whorled spines follows a basipetal sequence, the inverse of initiation. All elongated spines are at first erect, but the lateral ones become radially oriented as they appraoch maturity. Central spines remain erect and tilted slightly toward the shoot apex. The distal ends of many epidermal cells on developing spines bear conic projections that are most prominent along the median portions.
Abstract
Axillary meristems of Mammillaria elongata DC were studied with a scanning electron microscope using fresh tissue to determine their degree of development and suitability as explants in tissue culture investigations. Meristems were excised at regular intervals along the stem. The axillary meristem reached maximum size about 10 cm and maximum development about 15 cm below the stem tip. Axillary meristems closer to the base of the stem were less developed. In fully developed meristems, leaf primordia were initiated in a spiral acropetal sequence at the margins of the apical dome, resulting in a phyllotaxis of 8 + 13 contact parastichies of tubercles on the developed stem. Enlarged leaf primordia were 1- or 3-lobed and about 75 μm in length. No flower initiation or lateral branch development was observed; however, a corky region, the result of aborted or senesced flowers, was observed in several axils. Variability in development or absence of axillary meristems in several axils make M. elongata axillary meristems unsuitable for critical studies on factors influencing organogenesis in tissue culture.
Urea foliar sprays may be a more efficient and environmentally sound alternative to soil applied fertilizer N in the postharvest period in tree crop production in California. While tree crop sulfur (S) status can interact with tree N status to affect growth, we know of no study assessing tree crop leaf N and S dynamics following fall (postharvest) foliar urea applications. We conducted a field study to measure temporal dynamics of leaf N and leaf S (% dry weight basis) following postharvest urea sprays on prune (Prunusdomestica) and almond (Prunus dulcis). June-budded nursery stock prune (`French' on Myro 29C) and almond (`Price' on Lovell) trees were sprayed to dripping with 6.5% (w/w) and 10% (w/w) standard urea solutions, respectively. Prunes were sprayed on 1 Oct. 2003 and almonds on 18 Nov. 2003. Leaf samples were taken over a 3-week (almond) or 8-week (prune) period, beginning just before treatment. Foliar urea sprays significantly increased prune (23%) and almond (14%) leaf N compared to untreated control within 8 days of application. This affect was transient, as there were no differences in leaf N concentrations between treated and untreated trees at final leaf sampling. Urea sprays did not affect almond leaf S concentration relative to untreated trees. Prune leaf S was significantly reduced compared to untreated trees 8 days after treatment, but only on that sampling date. Remobilization of S from the leaves of control trees of either species was not apparent.
Abstract
The effects of 2 light levels, (full sun and 47% shade) 3 nitrogen and 3 potassium levels (672, 2018, and 3362 kg/ha yr-1) on light compensation point, shoot and root growth, canopy distribution and leaf tissue nutrient content of Ficus benjamina were determined. The 47% shade treatment during 7 months of production significantly decreased light compensation point levels. N level slightly affected compensation point and K level had no effect. Higher N levels increased shoot growth, while K levels played a dominant role in root development. Light level interacted with both of these effects. N level was positively correlated to percent of the plant canopy contained in the upper half of the plant and this in turn closely was correlated with plant light compensation point.