Repository logo

1980-1999

Permanent URI for this collection

https://hdl.handle.net/10217/100536

Browse

Browsing 1980-1999 by Subject "Acclimatization (Plants)"

Now showing 1 - 3 of 3
  • Thumbnail Image
    ItemOpen Access
    Physiological studies in acclimatization of in vitro tobacco plantlets
    (Colorado State University. Libraries, 1992) Safadi, Farida, author; Hughes, Harrison G., advisor; Morgan, Jack A., committee member; Towill, Leigh, committee member; Nabors, Murray, committee member
    Two acclimatization methods of in vitro tobacco (Nicotiana tabaccum 'Wisconsin 38') plantlets (IVP) were studied for their physiological effects upon plantlet response to transplanting: 1) the use of osmotica in rooting medium such as polyethylene glycol (PEG) or salts (NaCl + CaCl2) at different concentrations and durations, and 2) the use of semipermeable closures (SPC) which improves gas permeability of culture vessels. Concentrations of 1.0%, 2.5%, 5.0%, 10.0% and 15.0% PEG reduced water loss of detached leaves but affected growth adversely especially when above [5%] and 6-day-duration. PEG treatments induced epicuticular wax (EW) build-up and were related to reduced rates of water loss. Salt treatments reduced water loss at 1.5 and 2.0% over control but caused undesirable growth characteristics. Leaf diffusive resistance of PEG-treated plants was reduced prior to transplanting and remained lower than that of control. Stomates of IVPs had slower response to reduced humidity and darkness than greenhouse and PEG-treated plants. The SPC-treated cultures had 2.5 times more evapotranspiration, 2% less relative humidity (RH) and 3 times less medium and plantlet leaf water potential than B-cap-treated cultures. SPC treatments increased plantlet EW by 35%, reduced water loss by 60%, increased plantlet dry weights, reduced wilting injury and increased initial relative growth rates as compared to B-cap treatments. Photosynthetic rates of in vitro plantlets were reduced at RH lower than 80- 90%. SPC improved photosynthetic rates under desiccating conditions by reducing initial conductance and transpiration. Photosynthetic rates of IVPs from both closure treatments were comparable to those of greenhouse plants at high humidity. Stomates of plantlets from both treatments did not respond to [CO2] and darkness compared to stomatal responses of greenhouse plants. Chlorophyll content was increased in the SPC over B-cap plantlets. Better gas exchange of SPC was observed as indicated by CO2 accumulation. Although both osmotica and closure treatments reduced moisture loss in detached leaves of IVPs to levels comparable to those of greenhouse plants, the moisture loss curves deviated from normal bi-phasal shape indicating lack of normal stomatal functioning.
  • Thumbnail Image
    ItemOpen Access
    Rapid micropropagation of cocoyam (Xanthosoma sagittifolium) Schott
    (Colorado State University. Libraries, 1993) Sama, Anne E., author; Hughes, Harrison G., advisor; Johnson, Duane, committee member; Towill, Leigh, committee member
    Cocoyam (Xanthosoma sagittifolium Schott) was rapidly micropropagated through early subcultures at four and six week intervals and division of the microshoots. Shoot tips of approximately 3-5mm in size were used in the initiation of cultures on a modified B5 basal salt medium for six weeks. Cultures were subsequently micro propagated successfully through several procedures, which included the use of a range of growth regulator levels. Levels of 0.05μM NAA with 5, 10 and 20μM BAP as well as 1, 2 and 4μM TDZ singly or in combinations at the initiation and multiplication stages, as well as on agitated and stationary liquid media. Cultures initiation on solid media or supported on filter paper bridges was unsuccessful. However, solid media were beneficial in shoot multiplication, elongation and rooting stages. The level of 2μM TDZ alone and in combination with 20μM BAP significantly enhanced shoot proliferation, producing an average of 30 microshoots/culture, but repressed root formation. However, root initiation and development was possible in media containing only BAP at all levels tested. Shoot proliferation, elongation and rooting continued on media devoid of plant growth regulators and was independent of the culture vessel employed. A 100% survival of plantlets transferred into the greenhouse was achieved, irrespective of the method of acclimatization and size of the plantlet. Plantlets acclimatized in the humidity tent were less stressed, produced more and shed fewer leaves after two weeks from acclimatization. Differences in level of leaf injury were evident with control plants transferred directly to the open bench, which sustained the highest injury. The high level of survival of plantlets upon transfer to the greenhouse was attributed, in part, to the reduced numbers of stomates found on both abaxial and adaxial leaf surfaces of in vitro cultured plantlets, the high wax content and high rate of rooting.
  • Thumbnail Image
    ItemOpen Access
    Response of 'Red Lake' currant and Red-osier dogwood to cold acclimation
    (Colorado State University. Libraries, 1995) Hanna, Mark David, author; Stushnoff, Cecil, advisor; Klett, James E., committee member; McNeil, Michael, committee member
    Twigs of 'Red Lake' currant (Ribes rubrum L.) and Red-osier dogwood (Cornus sericea L.) were collected at the beginning of each month starting October 1992, and ending the first of April 1993. Twig samples were subjected to controlled temperature treatments: 0°C, 10°C, -5°C, 0°C for 12 hr/ 10°C for 12 hr, and -5°C for 12 hr/ 10°C for 12 hr for one month. Treated and field samples were evaluated for hardiness by freeze tests and glucose, sucrose, raffinose and stachyose content in cortical tissue. A study of hardiness was repeated the following year beginning in September and ending the first of April. Cold tolerance was promoted best by fluctuating temperatures in the fall with greater acclimation achieved in the colder temperature treatments as the season progressed until mid-winter and into the spring months when de-acclimation occurred. Hardiness was best retained by the cooler steady temperatures. The endogenous content of raffinose was strongly associated with cold hardiness in both plant materials. Raffinose and glucose levels of field samples from both currant and dogwood were significantly correlated with cold hardiness. Stachyose was also associated with hardiness of currant taken from outdoors and treated at 0°C. Sucrose was associated with hardiness in dogwood stored at -5°C/10°C. The best association between sugars and cold tolerance in either plant species was seen in samples taken directly from the field with no treatment. Storage at 0°C/10°C increased raffinose as hardiness increased in both species. Storage at 0°C and at -5°C increased raffinose as hardiness increased in dogwood. but not in currant. Warm temperature storage as 10°C and -5°/10°C destroyed the relationship between hardiness and raffinose levels in both plant materials.