玉米花粉单倍体植株染色体上异染色质的变异

我们用Giemsa BSG C-带技术检查了玉米花药培养获得的花粉单倍体植株根尖细胞染色体上异染色质的变异,观察结果表明,有的植株所显示的C-带数目是与供体植株的相一致,有的植株所显示的C-带数目则发生了显著变化,其中有的增加,有的减少。并讨论了异染色质发生变异的可能原因。还相应地观察到间期核中染色中心的变化是与中期染色体上C-带数目的变化相一致。     

Plant regeneration from hypocotyl and petiole callus of Trifolium pratense L.

Red clover (Trifolium pratense L.) seedlings were screened for the ability to regenerate plantlets from hypocotyl-derived callus tissue. Media sequences described by Beach and Smith (1979) and Collins and Phillips (1982) and a variation using media from both sequences were tested. Plantlets were regenerated from three out of 642 genotypes. In all three cases, callus was initiated on B5C medium and regeneration was accomplished on SPL medium. Attempts to regenerate plants from petiole-derived callus tissue have so far been successful only with regenerants of clone F49. Petiole callus from epicotyl-derived F49 plants proved to be non-regenerative. Pollen viability varied significantly among individuals regenerated from callus cultures of clone F49. Root tip squashes from F49 regenerants revealed the normal diploid chromosome number (2n=14). The frequency of regeneration within progeny from reciprocal crosses between F49 regenerants and several non-regenerative genotypes was 29%.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - BAP benzylaminopurine - KN kinetin - NAA -naphthaleneacetic acid     

Plant resistance, plant traits, and host plant choice of the leaf-folding sawfly on the arroyo willow

Abstract. 1. The hypotheses that genetic variation in host plant resistance of the arroyo willow affected leaf folder ( Phyllocolpa sp.) (Hymenoptera: Tenthredinidae) density and that genetic variation in shoot length and leaf length was correlated with resistance were tested.
2. Willows grown in pots and exposed to ovipojsition by the leaf folding sawfly in cages had significantly different densities among clones, indicating variation in resistance caused by genetic differences among conspecific host plants.
3. There was a general correspondence between leaf folder density on potted cuttings and on the plants in the field that were the sources of cuttings.
4. In behavioural choice experiments, susceptible clones (with highest leaf fold densities) had the highest oviposition activity of female leaf folders compared to clones that were resistant to the leaf folder.
5. Clones differed significantly in shoot length and leaf length among clones grown in pots, among clones in the field, and between shoots with galls and shoots without galls on clones in the field.
6. Leaf folder density was significantly positively correlated with mean shoot length on field clones in 1985 and 1986, but was not correlated with leaf length, although leaf length and shoot length were correlated.
7. Leaf length variation among willow clones accounted for a significant portion of the variation in resistance of potted willows, but shoot length was unimportant.     

Plant hormone response mutants

A variety of plant hormone response mutants has now been described, and is surveyed in this article. In addition to hormone-insensitive mutant phenotypes with defects in hormone-related features, there exist mutants apparently constitutive for the gibberellin responses, and also a mutant hyper-responsive to gibberellin. Although there is still little biochemical evidence on the nature of these mutants, the emerging picture of their genetic dominance relationships has given rise to tentative suggestions of the involvement of represser functions in hormonal control systems.     

The effects of microtubule and microfilament disrupting agents on cytoskeletal arrays and wall deposition in developing cotton fibers

Summary The effects of various cytoskeletal disrupting agents (cholchicine, oryzalin, trifluralin, taxol, cytochalasins B and D) on microtubules, microfilaments and wall microfibril deposition were monitored in developing cotton fibers, using immunocytochemical and fluorescence techniques. Treatment with 10^–4 M colchicine, 10^–6 M trifluralin or 10^–6 M oryzalin resulted in a reduction in the number of microtubules, however, the drug-stable microtubules still appear to influence wall deposition. Treatment with 10^–5 M taxol increased the numbers of microtubules present within 15 minutes of application. New microtubules were aligned parallel to the existing ones, however, some evidence of random arrays was observed. Microtubules stabilized with taxol appeared to function in wall organization but do not undergo normal re-orientations during development. Microtubule disrupting agent had no detectable affect on the microfilament population. Exposure to either 4×10^–5 M cytochalasin B or 2×10^–6M cytochalasin D resulted in a disruption of microfilaments and a re-organization of microtubule arrays. Treatment with either cytochalasin caused a premature shift in the orientation of microtubules in young fibers, whereas in older fibers the microtubule arrays became randomly organized. These observations indicate that microtubule populations during interphase are heterogeneous, differing at least in their susceptibility to disruption by depolymerizing agents. Changes in microtubule orientation (induced by cytochalasin) indicate that microfilaments may be involved in regulating microtubule orientation during development.     

Sensitive detection of mycoplasmalike organisms in field-collected and in vitro propagated plants of Brassica, Hydrangea and Chrysanthemum by polymerase chain reaction

A polymerase chain reaction (PCR) protocol, previously designed for amplification of a DNA fragment from aster yellows mycoplasmalike organism (MLO), was employed to investigate the detection of MLO DNA in field-collected and in vitro micropropagated plants. PCR with template DNA extracted from symptomatic, naturally-infected samples of Brassica, Chrysanthemum and Hydrangea, each yielded a DNA band corresponding to 1.0 Kbp. However, no DNA product was observed when either infected Ranunculus (with phyllody disease) or Gladiolus with (symptoms of ‘germs fins’) was used as source of template nucleic acid for PCR; further experiments indicated absence of target DNA in the case of Ranunculus and the presence of substances in Gladiolus which inhibited the PCR. The MLO-specific DNA was detected by PCR using less than 95 pg of total nucleic acid (equivalent to total nucleic acid from 1.9, ug tissue) in the case of field-collected Hydrangea and less than 11.4 pg of nucleic acid (equivalent to total nucleic acid from 19 ng of tissue) in the case of field-collected Brassica. The findings illustrate highly sensitive detection of MLOs in both field-grown and in vitro micropropagated infected plants.     

Aminoglycoside-3″-adenyltransferase confers resistance to spectinomycin and streptomycin in Nicotiana tabacum

The bacterial gene aad A encodes the enzyme aminoglycoside-3-adenyltransferase that confers resistance to spectinomycin and streptomycin in Escherichia coli. Chimeric genes have been constructed for expression in plants, and were introduced into Nicotiana tabacum by Agrobacterium binary transformation vectors. Spectinomycin or streptomycin in selective concentrations prevent greening of N. tabacum calli. Transgenic clones, however, formed green calli on selective media containing spectinomycin, streptomycin, or both drugs. Resistance was inherited as a dominant Mendelian trait in the seed progeny. Resistance conferred by the chimeric aad A gene can be used as a color marker similar to the resistance conferred by the streptomycin phosphotransferase gene to streptomycin.     

Plant regeneration from cotyledon protoplasts of Brassica carinata

Protoplasts isolated from cotyledons of Brassica carinata, underwent sustained division when cultured at 5.0 × 10⁴ ml^-1 in modified 8p medium (KM8P) with 1.0% (w/v) Seaplaque agarose. Cell colonies produced callus when agarose droplets, in which the protoplasts were embedded, were transferred to K8 medium with 0.6% (w/v) Sigma Type I or Type VII agarose at day 16, giving a plating efficiency of 1.6%. Seventy percent of the protoplast derived-tissues produced shoot buds after subculture to MS medium containing 3.0% (w/v) sucrose, 1.125 mgl^-1 BAP, 0.035 mgl^-1 GA and 0.6% (w/v) Type I agarose, resulting in shoot formation from 1.1% of the protoplasts originally plated. Protoplast-derived colonies transferred to hormone-free MS medium with 1.0% (w/v) sucrose and 0.6% (w/v) Type I agarose produced roots. The latter gave rise to shoots after excision from the parent callus and culture on MS medium with 3.0% sucrose, 0.225 mgl^-1 BAP, and 0.6% (w/v) Type I agarose. Shoots regenerated directly from protoplast-derived calli, or indirectly from roots, developed prolific root systems when placed on hormone-free MS medium with 1.0% (w/v) sucrose and 0.6% (w/v) Type I agarose.Abbreviations BAP 6-benzylaminopurine - CH casein hydrolysate - 2,4-D 2,4-dichlorophenoxyacetic acid - GA gibberellic acid - K kinetin - NAA -naphthaleneacetic acid - MES 2(N-morpholino)ethanesulphonic acid, 2,iP-6(,-dimethylallyamino) purine - IAA indole-3-acetic acid - Z zeatin - ZR zeatin riboside