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- Author or Editor: David Morgan x
New Guinea impatiens (Impatiens hawkeri Bull.) were grown in a recirculating ebb-and-flow subirrigation system under increasing levels of salinity stress from a mixture of NaCl and CaCl2 (1:1 equivalent ratio, 2:1 molar ratio) and recommended production levels of other nutrients. Growth and quality decreased as salinity level increased, with a 75% to 80% growth reduction at 18 mol·m-3 NaCl-CaCl2 compared to controls. Among controls, root mass distribution was 10%, 50%, and 40% in the top, middle, and bottom layers of the root zone, respectively. In the highest salinity treatment (18 mol·m-3 NaCl-CaCl2), most of the root mass was in the middle layer (80%), while the root mass in the top and bottom layers was reduced to 5% and 15%, respectively. The electrical conductivity (EC) of the growing medium was high in the top layer in all treatments, but only exceeded maximum recommended levels in the middle and bottom layers in the 4·mol·m-3 or higher treatments. Initial postproduction leaching caused the salts in the top layer to migrate to the middle and bottom layers, which in some experiments induced a rapid and transient wilting. Up to six leaching and drying cycles of a 0.20 leaching fraction were required to reduce EC in all layers to recommended levels. Overall, salable plants of good quality and size were produced with up to 2 mol·m-3 (total 152 mg·L-1) NaCl-CaCl2 in the recirculated nutrient solution.
Nitrogen applied to ‘Roosevelt’ Boston fern in the greenhouse at 0, 25, 50, 100, 200, and 300 ppm concentrations increased dry weight, frond length, and leaf area up to 200 ppm, but all decreased at 300 ppm.
In greenhouse studies, maximum growth of Nephrolepis exaltata (L.) Schott ‘Rooseveltii’ was obtained in an acid (pH 4-5) medium. Dry weight of ferns decreased as pH of the medium increased.
Mature acorns of the live oak (Quercus virginiana Mill.) were immersed for 0-60 minutes in 43.3 to 60.0°C (110 to 140°F) water baths. Various of those treatments produced up to 100% control of larvae of acorn weevils (Curculio sp.) in the seeds, but reduced acorn germination and radicle length to varying degrees.
Ficus benjamina L. and F. stricta Miguel. were exposed to various concentrations of ethylene gas and ethephon to determine their sensitivity to defoliation. F. stricta was more sensitive to ethephon, whereas F. benjamina was more sensitive to ethylene gas. Plants growing in medium exposed to ethylene gas depleted ethylene from the ambient atmosphere. Double-autoclaving the peat : perlite growing medium prevented ethylene depletion, indicating soil microbes as the source of depletion. Bacterial isolates from the medium depleted ethylene in vitro; fungal isolates did not deplete ethylene. The eight species of bacteria isolated into pure culture depleted 9% to 46% of the ethylene from the flask atmosphere over 5 days, with two Enterobacter spp. and one Pseudomonas sp. being the most effective depleters. Chemical name used: (2-chloroethyl)phosphonic acid (ethephon).
Live oak (Quercus virginiana Mill.) acorns harvested for commercial seedling production frequently are heavily infested by larvae of Curculio spp. (2). Many nurserymen routinely soak acorns for 30 min in 49°C water to kill weevil larvae before planting the seed (4). Microwave radiation is effective against some stored products pests, but it is too damaging for use against acorn weevil larvae (2). Crocker and Morgan (1) measured the short-term (12-day) effects of hydrothermal treatments of tree-harvested acorns on survival of weevil larvae and seed germination, using 0- to 60-min immersion of the seed in 43.3° to 60.0° baths. Treatment for any of the tested times at a minimum of ≈49° controlled 100% of the weevils; it also produced dosage-related plant mortality and reduction in the short-term growth of seedlings. In the present research, we examined the survival and long-term vigor of acorns that were exposed to a 49° hydrothermal treatment.
The time to harvest maturity of flowering shoots and the extent and source of variability in maturity dates differed among cultivars of gentian (Gentiana sp.), with a wider spread in time to harvest maturity in Showtime Starlet (41 days) than Showtime Diva (35 days) and Showtime Spotlight (29 days). Cultivars also differed by more than twice in their plant-to-plant variability in time to harvest. Although later-emerging shoots reached harvest maturity more quickly than earlier-emerging shoots, the use of growing degree-days (GDD) for this field-grown cut flower did not account for differences. For ‘Showtime Diva’, 77% of outliers reached harvest maturity at the beginning of the season (i.e., before the 10th percentile). For ‘Showtime Spotlight’, only 20% of shoots classified as outliers flowered early with the remaining 80% emerging late (i.e., after the 90th percentile). Strategies to control the spread in time to harvest maturity in late-maturing cultivars such as Showtime Starlet should focus on uniform shoot emergence and controlling temperature during growth. Although strategies to achieve uniform shoot emergence should also be targeted for ‘Showtime Diva’, controlling temperature during the growing season would not appear to offer significant control of the spread in time of harvesting floral shoots. However, in earlier-maturing cultivars such as Showtime Spotlight, strategies will primarily require a greater understanding of the factors influencing the variability in maturation of shoots within individual plants before, and after, emergence.
Cut flower productivity and quality of gentian is associated with growth and development of crown buds. Experiments were carried out with the gentian cultivar Showtime Diva to identify the response to treatments that break dormancy [cold temperature (chilling), gibberellic acid (GA3)] applied at different stages of development of crown buds (plants with nonemerged crown buds, shoots recently emerged, or shoots emerged and elongated). The comparative growth potential of crown buds within the cluster was also investigated. At the stages of development examined, the application of GA3 (100 ppm) increased emergence of crown buds as shoots, leading to development of more flowering shoots. A similar response was observed with exposure to cold, but only on plants with nonemerged crown buds. Shoot emergence increased in response to increased duration of cold from 0 to 42 days (5 °C). Both chilling and GA3 could potentially be used to reduce the duration to, and spread of, harvest maturity if applied before shoot emergence. The hierarchical relationship of buds in crown bud clusters led to differential responses to application of GA3. Buds ontogenetically positioned at the proximal end of the bud cluster took a similar duration to reach shoot emergence or harvest maturity. For buds located at the distal end there was a positive correlation between ontogenetic bud position and the duration to reach shoot maturity. Shoot length and number of nodes at harvest maturity showed slight negative correlations with the position of the bud in the bud cluster. The results provide an explanation for possible sources of the variation in quality and quantity of floral shoots, and spread in time to harvest maturity within a single plant, and with development stage.
In an elective course titled “Be A Master Student”, freshmen in The Pennsylvania State Univ.'s College of Agricultural Sciences were introduced to subjects ranging from university policies and procedures to skill enhancement in note-taking, test-taking, and time management techniques. A broad knowledge of agricultural sciences at local, state, national, and international levels was developed with the goal to relate agriculture to individual and societal needs. Mentoring relationships between students and faculty developed, not only with course instructors, but also with other faculty through required interviews and one-on-one discussions. Two volunteer faculty instructors taught 20 students per section. The number of sections has increased from four in 1990 to 13 in 1994. More than 70% of incoming freshmen opted to schedule the course in 1994. Student surveys indicated that >90% of those who enrolled would recommend the class to a close friend. Performance tracking shows that studentswho enrolled in the class maintained higher grade point averages than students who did not enroll. A higher rate of retention also has been documented for students who complete “Be A Master Student”!
Shoot productivity and overwintering survival of gentians (Gentiana sp.) are determined by the initiation and subsequent development of crown bud clusters. Understanding of the anatomical features and origins of crown buds and bud clusters, and plant ontogeny, the morphological features of crown buds, and their associated development is required to achieve manipulation of bud initiation, emergence, and development. Anatomical features of the crown bud clusters were examined using both light and confocal microscopy using hybrids of Gentiana triflora × G. scabra. The initiation of bud clusters presented characteristics typical of adventitious buds in terms of their origin and presence of external vascular connection to the parental tissue. In contrast, crown buds forming subsequently within the cluster developed as axillary buds within that initial bud, collectively forming on a compact stem with minimal internode elongation. Stem elongation within the cluster after application of gibberellic acid enabled identification of a hierarchical arrangement of buds within the cluster with one bud at each node and arranged spirally at 90°. Arrangements of buds within the cluster were different from the opposite decussate phyllotaxis in floral shoots with two axillary buds at each node. Based on the current study, a crown bud cluster originated from a first bud initial, which was adventitious followed by development of subsequent crown buds within the cluster as axillary buds from this first bud initially with a single bud developing at each node.