Search Results

You are looking at 21 - 30 of 46 items for :

  • Author or Editor: Harrison Hughes x
  • HortScience x
Clear All Modify Search

Research involving acclimatization of in vitro plantlets by reducing the relative humidity (RH) in vitro requires a suitable method for monitoring RH in the culture vessels. In this research we describe a method for measuring the RH dynamically in the culture vessels, based upon thermocouple psychrometry. Thermocouple junctions (.003 mm gauge) were used with a wet cotton thread on the wet bulb junction inserted from the side of the jar. Aspiration was provided by tiny fans run by miniature motors left outside the vessels. Pre-calibrated aspirated and non-aspirated experiments showed realistically reduced RH in the cultures covered with caps which allowed for gas exchange. The aspirated procedure resulted in greater precision. This procedure with some refinement could be a useful method for monitoring RH in in vitro cultures.

Free access

Shoot tips, approximately 3-5mm, were isolated from corms of young greenhouse-grown plants of cocoyam, cultivar South Dade White. After preliminary evaluations, the initiation media evaluated were B5 basal salts supplemented with 0.05 μM NAA with 5μM BAP, 20μM BAP or 2μM TDZ. The above media were in the form of liquid medium in flasks on a rotary shaker, liquid medium with filter paper bridges, stationary liquid medium without filter paper and solidified medium with 0.4% agar. TDZ stimulated greater growth with multiple shoot formation. Liquid media either in the shaker or stationary form were more effective in terms of growth. Shoots were subsequently evaluated for multiplication with 1μM TDZ and 5μM BAP with 0.05μM NAA producing greater shoot numbers. Over 30 plants have subsequently been rooted and acclimatized under mist or humidity tent.

Free access

Alstroemeria is an important cut flower in the U.S. due to their wide variety of colors and to their long vase life. The most commonly grown cultivars were developed in Europe and their parentage has never been fully divulged. We are attempting to determine the probable parents of many of these cultivars through karyotype analysis and giemsa banding. Although preliminary karyotype analyses are available for 10 species and 25 cultivars, detailed karyotype analyses of only A. pelegrina and A. ligtu hybrids have been completed. Detailed karyotype analyses are now complete for 7 more species of Alstroemeria as well as the related genera Leontochir and Bomarea and 23 cultivars. A comparison among species and cultivars will be presented reflecting probable parentage of the cultivars. Results of giemsa banding will also be presented to further clarify cultivar parentage and relationships. This information should facilitate the more rapid development of successful cultivars by breeders in the U.S.

Free access

The Dept. of Horticulture and Landscape Architecture offers majors in Horticulture with four concentrations (Floriculture, Horticultural Business Management, Horticultural Food Crops, and Horticultural Science) and Landscape Horticulture with three concentrations (Landscape Design and Construction, Nursery and Landscape Management, and Turf Management). A third major in Landscape Architecture is also offered. The department maintained the concentrations in past years of low enrollment by switching courses to alternate years, dropping nonmajor courses, and through hiring part-time staff. Currently, increasing enrollments, with limited additional funding and the need for broadened general requirements, increased career guidance, and capstone courses have increased pressures on consolidation of concentrations. Faculty have refocused senior courses to create capstone courses in several concentrations, moved the senior seminar to sophomore status for career enhancement, and are currently discussing other options.

Free access

Isozyme analysis was used to characterize and identify 24 species, hybrids, and color variants of Alstroemeria, two plants of Leontochir ovallei, and one plant of Bomarea. A single technique was developed for the extraction of seven enzyme systems (PGM, PGI, 6-PGD, EST, ME, AAT, and LAP) that exhibited a high level of polymorphism. Between 11 and 18 of the species and hybrids could be identified uniquely for each of the first six enzyme systems. The final system, LAP, was tested on only 11 species and hybrids, and nine different patterns were identified. Using only three of the seven enzyme systems, it was possible to uniquely identify all of the species and hybrids investigated.

Free access

Crosses and self's were made among Fragaria × ananassa Duchn. cv. `Douglas' and `Fern' and Fragaria chiloensis (L.) Duchn. Seeds were surface sterilized, germinated and then grown on MS media (no vitamins, sucrose or hormones) with NaCl concentrations of 0 to 0.5% or 0.5% KCl. Polyethylene glycol (PEG), of corresponding water potentials, was used to induce drought stresses. Whole plant dry weights were evaluated after 50 days. Differences in salt tolerance were associated with genotype; progeny involving crosses with F. chiloensis showed greater salt tolerance. Increases in concentration of PEG caused decreased growth. The use of salt containing media may be used to evaluate strawberry seedlings for salt tolerance and, similarly, PEG may be used to evaluate for drought stress in vitro.

Free access

In recent years there has become an increased demand for native, drought-tolerant species for private landscaping and revegetation of disturbed sites; especially in the Rocky Mountains and high plains states. Sheperdia canadensis and S. rotundifolia, native to much of this area, have already increased in popularity due to their drought tolerance and general hardiness. Micropropagation and rooting of cuttings have been investigated for these two species. S. canadensis hardwood stem cuttings were successfully rooted with 0.8% IBA at 46.5% as compared to less than 5% from previous research. S. rotundifolia produced a greater number of axillary shoots on WPM as compared to MS medium and at a moderate concentration of BA.

Free access

The evergreen Ceanothus velutinus and semi-evergreen C. fendleri are native Colorado, drought-tolerant shrubs. They are of interest for landscaping and rock gardens, but have poor seed germination as well as vary considerably in growth form and habit. Asexual propagation methods would be important for commercial development of these species. Basal hardwood cuttings of C. velutinus were rooted using four different concentrations of IBA. The highest concentration of IBA (0.8%) showed the highest rooting (14.8%), while the average number of roots per cutting was highest for 0.1%. Ceanothus fendleri shoot tips were cultured on MS medium with four BA (0.89, 4.4, 8.9 and 17.8 μM) and three 2ip concentrations (24.6, 49.0 and 73.6 μM). After nine weeks an average of six shoots were produced in treatments having 4.9 μM of BA. Lower concentrations of BA up to 9.8 μM were better than higher concentrations of BA or 2ip. There was a tendency for production of callus at the higher levels of 8A and all levels of 2ip.

Free access

Scanning electron microscopy was used to study stomatal function of grape (Vitis sp. `Valiant') plantlets grown in vitro, polyethylene glycoltreated (PEG) in vitro and greenhouse. Fully open stomata were observed in in vitro grown plants with large aperture (13.5μm) as compared to narrow stomatal opening and small aperture in PEG-treated (4.9pm) and greenhouse grown plants (3.2μm). Furthermore, stomates of persistent leaves initiated during in vitro culture remained fully open with large apertures (12.8μm) two weeks after transplanting in the greenhouse. In contrast, newly-formed leaves produced in the greenhouse from in vitro cultured plants showed narrow stomatal opening with small apertures (3.3μm). In vitro produced leaves exhibited rapid wilting followed by irreversible tissue damage and severe desiccation within three hours of transplantation into the greenhouse. However, PEG-treated plantlets showed a reduced stomatal opening with associated minimal stress when directly transferred into the greenhouse. Thus use of an osmotic agent, PEG, induced more normal stomata1 function as well as improved survival after transfer to the greenhouse.

Free access

Scanning electron microscopic (SEM) studies and gravimetric analysis of in vitro cultured leaf surfaces showed reduced epicuticular wax (EW) structurally and quantitatively as compared to greenhouse plants. However, leaves of in vitro plantlets subjected to polyethylene glycol-treatment (PEG) showed an increase in quantitative and structural EW which was similar to that of greenhouse plants. Furthermore, leaves initiated during in vitro culture and which persisted, when transferred to the greenhouse, showed an increase in structural wax as well as in amount, 30 days after transplanting in the greenhouse. Similarly, leaves newly-formed in the greenhouse from in vitro cultured plants developed more dense crystalline structure and greater levels of wax than those leaves observed immediately after removal from culture. A correlation between density of structural EW and amount of EW were observed in in vitro cultured, PEG-treated in vitro cultured and greenhouse grown leaves.

Free access