Abstract
Endogenous gibberellins (GA) and cytokinins (CK) were extracted from asparagus (Asparagus officinalis L.) spear tips, purified, and determined by lettuce hypocotyl and amaranthus bioassays, respectively. There was no quantitative difference in GA-Iike activity between heterogametic male and female spears. The major GA fraction in asparagus spears has 1 OH group. Asparagus spears contain 3 major fractions of CK-like activity. Fraction 1 eluted from Sephadex LH-20 and C18 HPLC columns with or before zeatin-riboside. Fractions 2 and 3 eluted in a similar pattern to IPA-riboside and IPA, respectively. There were higher levels of CK fraction 2 and trends toward higher levels of fraction 1 and total CK in female than in heterogametic male spears. There were also higher CK:GA ratios in female than in heterogametic male spears. The data support the hypothesis that sex in asparagus is controlled in part by CK levels or by CK:GA ratios.
Abstract
Leaf cuttings of Rieger elatior begonias (Begonia bertini ‘compacti’ × B. socotrana cvs. Aphrodite Cherry Red and Schwabenland Red) were treated with 6-furfurylamino purine (kinetin), 6-benzylamino purine (BA), and 6-(benzylamino)-9-(2-tetrahydropyranyl)-9H-purine (PBA). BA and PBA enhanced bud and shoot regeneration in ‘Aphrodite Cherry Red,’ while kinetin showed no activity. All cytokinins tested reduced shoot development in ‘Schwabenland Red.’ PBA stimulated optimal bud and shoot development when applied to ‘Aphrodite Cherry Red’ leaf cuttings as a 12 hour 15 μM basal-petiole dip, 1000 μM spray, and 0.01% talc-petiole- dip. Cuttings taken from ‘Aphrodite Cherry Red’ stock plants treated with 1000 μM PBA successfully generated new plants.
Three strawberry cultivars were used in this study. Runners from the three cultivars were grown on Murashige and Skoog medium supplemented with benzylaminpurine or kinetin at four concentrations (2, 1, 0.5, and 0.25 mg·L-1 in addition to the control treatment). The use of cytokinin, regardless of type and concentration, promoted the explant proliferation, shoot height, number of leaves, and plantlet fresh weight. Callus formation was enhanced by BA application, especially with `Pajaro'. However, `Chandler' did not form at all using cytokinin. Produced plantlets had lower nutrient constituents (N, P, K, Ca, and Na) when grown on media containing cytokinin compared to the control. Based on these results, cytokinin is recommended to get more shoots per explant. Furthermore, using the lowest concentration (0.25 mg·L-1) will produce height proliferation, greater shoot length, and more leaves.
Ungrafted trees of seven apple rootstock cultivars, M.4, M.7, M.11, M.26, M.27, MM.106, and Maru. bakaidou (Malus prunifolia Borkh. var. ringo Asami; weeping type), and `Fuji' (Malus domestics Borkh.) trees grafted on these seven plus M.9 and M. 16 rootstock were grown in sand. They were regularly supplied with nutrient solutions of N as ammonium alone (A), nitrate alone (T), and both (AT). With both ungrafted and grafted trees, the shoot growth of six rootstock (M.11, M.4, M.7, MM.106, M.26, and M.27) was significantly less with A than with T. With `Fuji' trees grafted on the above six rootstock, the number of flowering buds and the ratios of flowering buds to total emerged buds were significantly enhanced by treatments A and AT, especially in the formation of axillary flowering buds. Flowering and shoot growth of `Fuji' trees grafted on M. prunifolia and M.16 were slightly affected by the form of supplied N. In the xylem sap, cytokinin-like activity was detected in a single zone in paper chromatography in all rootstock and `Fuji' trees. The activity in six ungrafted rootstock (M.4, M.7, M.11, M.26, M.27, and MM.106) and `Fuji' trees grafted on these plus M.9 rootstock were higher with A than with T. Gibberellin-like activity in the same sap was detected in two zones, Rfs 0.3 to 0.4 and Rfs 0.7 to 0.8 in paper chromatography. In the six ungrafted rootstock and in `Fuji' trees grafted on these plus M.9, A led to higher activity at Rfs 0.7 to 0.S, but T led to higher activity at Rfs 0.3 to 0.4. Cytokinin-like and gibberellin-like activities in ungrafted M. prunfolia and `Fuji' trees grafted on M. prunifolia or M.16 were not affected by the form of N.
Adventitious shoots can be regenerated from leaf explants of American elm (Ulmus americana L.), but the effects of cytokinins and donor plants were unknown. The goal of this study was to examine factors that influence regenerative capacity of American elm leaves. Excised leaves from 2-year-old seedlings were surface sterilized, and 1 cm2 sections were taken from the midrib portion of the leaves. Three to six seedlings were used as donor plants in various experiments. Zero, 7.5, 15, or 22.5 μM of benzyladenine (BA), thidiazuron (TDZ), kinetin, zeatin, or 2iP were added to Driver Kuniyuki Walnut (DKW) medium. Basal medium (DKW and Murashige and Skoog [MS]) effects on shoot regeneration were also examined. Leaves placed on media with BA or TDZ formed adventitious shoots, with TDZ inducing the highest percentage of regeneration. The donor plant also affected the efficiency of shoot regeneration, with certain seedlings having 1.5 to 7 times more explants forming shoots compared to others. Leaf explants from donor plants with the highest regenerative capacity had a higher percentage of regeneration on DKW than MS medium. Explants from productive donor plants should be placed on DKW medium supplemented with TDZ to improve shoot regeneration efficiency from American elm leaves.
To characterize the in vitro behavior of Rhododendron `Montego' with tissue proliferation (TP) to cytokinin and auxin, comparisons were made of normal [TP(–)], dwarf TP [TP(+) dwarf], and long TP [TP(+) long] shoot cultures. On basal medium TP(–) and TP(+), long shoots failed to multiply and had a low relative growth rate (RGR) of 0.1, whereas TP(+) dwarf shoots produced 31.8 shoots per tip, with most shoots being <5 mm long, and RGR was 0.3. Addition of 15 μm 2iP to basal medium induced the production of more than six shoots per TP(–) tip and doubled their RGR; TP(+) long shoots produced 16.8 shoots, most <5 mm long, and had an RGR of 0.3; TP(+) dwarf shoots produced only 16% as many shoots as on basal medium, but still exhibited an increase in RGR. Leaves from TP(–) and TP(+) sources failed to produce shoots on basal medium, but 74% of TP(–) leaves formed shoots when cultured on 1 μm IBA and 30 μm 2iP. TP(+) leaves were able to form shoot meristems on media containing only 5 μm 2iP (26% of explants), but these meristems failed to elongate into shoots. Calli from TP(–) leaves, TP(+) leaves, and TP(+) tumors grown on medium containing 10 μm NAA and 15 μm 2iP had higher RGRs than the same calli on basal medium during the first 8 weeks of culture. Over time, RGR decreased in both TP(–) and TP(+) leaf calli, but increased in TP(+) tumor callus. The increased RGR resulted from differentiation of shoot meristems on 85% of the calli between week 4 and week 8. Our results suggest that TP(+) tissues have altered hormone metabolism or sensitivity that leads to dramatic differences in in vitro behavior and probably contributes to tissue proliferation observed in whole plants. Chemical names used: 6-(γ,γ-dimethylallylamino) purine (2iP); indole-3-butyric acid (IBA); α-naphthaleneacetic acid (NAA).
Abstract
Shoot tips collected in June from ‘Summerland Red McIntosh’ (nonspur), ‘Macspur’, ‘Morspur’, and ‘McIntosh Wijcik’ apple (Malus domestica Borkh.) were examined for polar and less-polar gibberellins (GAs) and for cytokinin-like bioactivity. The latter three strains are increasingly compact and spurry, with ‘McIntosh Wijcik’ exhibiting a distinctive columnar growth habit. ‘McIntosh Wijcik’ shoot tips exhibited significantly lower levels of polar GAs, but the levels of less-polar GAs were similar in all four strains. Conversely, ‘McIntosh Wijcik’ displayed higher levels of cytokinin-like substances than the other three strains. These results are discussed in relation to the physiology of the spur-type growth habit of ‘McIntosh Wijcik’ apple and its progeny.
Abstract
Ethylene evolution from callus tissue of rose (Rosa hybrida L.) grown in air tight vessels was enhanced by the presence of auxin and cytokinin in the culture medium. Increased ethylene levels did not adversely affect the fresh weight gain of rose callus tissue.
-sterilized frond tips were inoculated on 1/2 MS media ( Murashige and Skoog, 1962 ) that contained cytokinin, 3% (w/v) sucrose, and 0.7% (w/v) plant agar and adjusted to pH 5.8 before being autoclaved. Using plant growth regulator (PGR)-free 1/2 MS medium as a
Lycopersicon esculentum cv. UC82b cotyledons were co-cultivated with A. tumefaciens carrying vectors with modified isopentenyl transferase (ipt) genes. The ipt gene was placed under the control of the RUBISCO promoter in both the sense and antisense orientation. Over 50 transformants were recovered on kanamycin-containing media. Seeds from RO plants were germinated on selective media and R1 plants transformed with the ipt gene identified by PCR and Southern blot hybridization. Phenotypes of the R1 plants, whether transformed with the ipt gene in the sense or antisense orientation, were comparable to the control plants transformed with an inactive cytokinin gene. Fruit weights from both were similar to those from control plants, however, yields were reduced and ripening delayed. Most fruit had no seeds or very few small seeds. Cytokinin levels are being determined in order to correlate them to the observed phenotypes.