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- Author or Editor: Athanasios S. Economou x
Abstract
Plant growth and development depend on light for photosynthesis and photomorphogenesis (22, 31, 45). Plant tissue cultures also require light, but to a lesser degree, to regulate mainly morphogenetic processes (34, 43, 50). The effect of light on photosynthesis of in vitro cultures is of less importance than that of in vivo plants (16). Light influences micropropagation success through its three parameters of duration (photoperiod or day length), illuminance (intensity or photon flux), and spectral quality (wavelength). This influence can be exerted directly on the in vitro cultures or indirectly as an after-effect to the subsequent culture.
Abstract
Shoot proliferation of Gardenia jasminoides Ellis was achieved from cultured shoot tips on a low salt medium supplemented with 25–98 μm (5–20 mg/liter) 2iP after 10 weeks. Reculture of the remaining tissue onto the same medium, after shoot removal, resulted in new shoot proliferation in 6 weeks. These microshoots rooted readily when excised and inserted into sphagnum moss peat under high humidity. Chemical name used. 2iP: N-(3-methyl-2-butenyl)-lH-purin-6-amine.
Abstract
Shoot tips of azalea (Rhododendron spp.) accessions 620014, 800057, and 800374 multiplied rapidly when cultured on a Murashige and Skoog (MS) medium modified by reducing concentrations of NH4NO3 and KNO3, adding (NH4)2SO4 (to give an
Abstract
Differences were observed in microcutting harvests from 5 shoot tip explant sequential recultures of the hardy deciduous azalea (Rhododendron spp.) accessions 800374, 620014, and 800057. In general microcutting production increased and then declined over reculture times in a nearly bell-shaped curve for all 3 clones tested. Maximum numbers of usable microcuttings were harvested in the 3rd and 4th recultures. Productivity varied among the 3 clones, with accession 800374 the most prolific and accession 800057 the least. The microcutting height was the same for all 5 recultures of accessions 800374 and 620014, whereas, in accession 800057 the height declined from the 1st through the 5th reculture. The microcutting quality rating was similar throughout all recultures of accessions 800374 and 620014, but accession 800057 produced higher quality microcuttings in the 3rd reculture than in the 5th reculture. Rooting of microcuttings in soilless medium increased from the 1st to the 5th reculture for all 3 clones, reaching more than 97% for the last 2 harvests.
Abstract
Shoots harvested from the first and 2nd reculture of azalea (Rhododendron sp.) accession 800374 shoot tip cultures grown under 16 hr photoperiod from cool-white fluorescent light were taller and achieved higher quality ratings than shoots from 24 hr daily photoperiod. The number of shoots produced during the first reculture was the same for both 16 and 24 hr photoperiod, whereas significantly more shoots were harvested from cultures grown under 16 hr in the 2nd reculture. Similarly, 24 hr light inhibited elongation of shoots and decreased quality rating from in vitro-derived shoot cultures without any effect on the number of shoots per culture. Photosynthetic photon flux density (PPFD) of 30 and 75 μmol s−1m−2 (400–700 nm) increased number, length, and quality rating of shoots harvested from in vitro-derived shoot explants when compared to a 10 μmol s−1m−2 PPFD. However, recultured in vitro-derived shoot explants produced similar number and length of shoots under 10, 30, and 75 μmol s-1m-2, whereas the quality rating was reduced in cultures under 75 μmol s−1m−2. The highest percentage of rooting occurred in microcuttings harvested from cultures grown under 10 and the lowest under 75 μmol s−1m−2. Increasing the PPFD from 10 to 75 μmol s−1m−2 reduced shoot length and quality rating of rooted microcuttings, as well as root length and quality rating.
Abstract
Sphagnum peat (peat) media (adjusted to pH 4.0, 4.6, 5.5, 6.6, and 7.4 with ground dolomitic limestone) and unadulterated peat (pH 3.6) were tested for their effectiveness on rooting of hardy deciduous azalea (Rhododendron sp.) microcuttings in high-humidity chambers. Rooting of more than 90% occurred in media with pH 4.0, 4.6, and 5.5; however, a) shoot height and quality rating and b) root length and quality rating were superior at pH 4.0. Clonal differences in rooting percentages were found for 3 clones of azalea microcuttings rooted in 5 soilless mixtures. A mixture including equal parts (v/v) of peat and either sphagnum, vermiculite, or perlite, or a combination of 2 peat : 1 vermiculite : 1 perlite (by volume) increased rooting percentages over peat alone for all 3 azalea clones examined.
Abstract
Leaf explants from ‘Sugar Daddy’ and ‘Sugar Plum’ petunia (Petunia hybrida L.) were pretreated in solutions of 0, 200, 400, and 800 mg/liter 6-benzylamino purine (BA) and were placed in a cytokinin-free modified Murashige and Skoog (MS) medium, to which 0.05, 0.1, or 0.2 mg/liter naphthaleneacetic acid (NAA) were incorporated to test interaction. NAA at 0.05 or 0.1 mg/liter increased shoot number, fresh weight, and shoot quality rating for ‘Sugar Daddy’, while in ‘Sugar Plum’ addition of NAA increased shoot fresh weight and improved shoot quality rating without any effect on shoot number.