An uncommon plant growth regulator, diethyl aminoethyl hexanoate, is highly effective in tissue cultures of the important medicinal plant purple coneflower (Echinacea purpurea L.).

We investigated the effects of various concentrations of diethyl aminoethyl hexanoate (DA-6) on the regeneration and growth of adventitious buds in in vitro purple coneflower cultures. Among the 3 types of explants tested, leaf explants required higher concentrations of DA-6 than petiole and root explants in order to obtain high regeneration rates, while root explants required the lowest concentration of DA-6. Additionally, explants with higher ploidy levels were more sensitive to the addition of DA-6, while explants with lower ploidy levels required higher concentrations of DA-6 to achieve its maximal regeneration rate. Interestingly, the application of a concentration that was conducive to the regeneration of explants with lower ploidy levels was inhibitory to the regeneration of explants with higher ploidy levels. Moreover, during the growth of regenerated buds, DA-6 application significantly improved plant height and weight, root weight, root thickness, root number, primary root length, total root length, and root/top ratio. Differences in the responses of explants to supplementation with DA-6 were also observed among explants with different ploidy levels, with buds having lower ploidy levels responding to lower concentrations of DA-6. Taken together, the results of the present experiments showed that proper application of DA-6 could increase in vitro culture efficiency in purple coneflower.

Induction of tetraploids from petiole explants through colchicine treatments in Echinacea purpurea L.

Petiole explants were obtained from in vitro grown diploid (2x = 22) Echinacea purpurea plantlets. Shoots were regenerated by culturing the explants on MS basal medium containing 0.3 mg/L benzyladenine (BA), 0.01 mg/L naphthaleneacetic acid (NAA) and four concentrations (30, 60, 120, and 240 mg/L) of colchicine for 30 days, or 120 mg/L of colchicine for various durations (7, 14, 21, and 28 days). The regenerated shoots were induced to root on MS basal medium with 0.01 mg/L NAA, and then the root-tips of the regenerated shoots were sampled for count of chromosome number. It was found that a treatment duration of >7 days was necessary for induction of tetraploid (4x = 44) shoots, and treatment with 120 mg/L colchicine for 28 days was the most efficient for induction of tetraploids, yielding 23.5% of tetraploids among all the regenerated shoots. Chimeras were observed in almost all the treatments. However, the ratio of tetraploid to diploid cells in a chimeric plant was usually low. In comparison with diploid plants, tetraploid plants in vitro had larger stomata and thicker roots with more root branches, and had prominently shorter inflorescence stalk when mature.

[Effects of silicon on flowering Chinese cabbage's anthracnose occurence, flower stalk formation, and silicon uptake and accumulation].

Different concentrations of silicon (Si) were applied to flowering Chinese cabbbage (Brassica campestris L. ssp. chinensis var. utilis Tsen et Lee) to study their effects on the flowering Chinese cabbage's anthracnose occurrence, flower stalk formation, and Si uptake and accumulation. The results indicated that Si could obviously control the occurrence of anthracnose, and the effect was genotype-dependant. The plants of susceptible cultivar applied with 2.5 mmol L(-1) Si and those of resistant cultivar applied with 0.5 mmol L(-1) Si exhibited the highest resistance to Colletotrichum higginsianum, with the lowest disease index and the higheist flower stalk yield. Si application also obviously affected the quality of flower stalk. For susceptible cultivar, Si application promoted the synthesis of chlorophyll, crude fiber and vitamin C, and induced the formation of soluble sugars. The contents of chlorophyll and crude fiber increased with increasing Si level. For resistant cultivar, the chlorophyll content increased while vitamin C content decreased with increasing Si level, but Si application had less effect on the contents of crude fiber and soluble sugars. For both cultivars, Si application did not have significant effect on the contents of crude protein and soluble protein but remarkably increased the Si accumulation in plant leaves, and the leaf Si content was significantly increased with increasing Si level. The Si granules deposited in leaf tissues were not equal in size, and distributed unevenly in epidermis tissues. It was concluded that the accumulation of Si in leaves could increase the resistance of plant to anthracnose, but there was no linear correlation between the accumulated amount of Si and the resistance.

[Effect of phosphorus deficiency on alternative respiratory pathway and its relation with O2-* accumulation in suspension-cultured tobacco cells].

Effects of phosphorus deficiency on alternative respiratory pathway and its relation with O(-.)(2) production were investigated in two lines of suspension-cultured tobacco cells which have different tolerances to P deficiency. Oxford cells were shown to be much more tolerant than K326. There were no apparent differences in inorganic and total phosphorous content between the two cell lines. The capacity and activity of alternative respiratory pathway were decreased by P deficiency in K326 cells but were little influenced in Oxford cells. Under either P-deficient or sufficient condition, the capacity and activity of alternative respiratory pathway were always higher in Oxford than in K326. When mitochondria were isolated and used for the same study, similar results were obtained as described above. The expression of AOX at protein level was induced by P deficiency in both lines to similar extents. O(-.)(2) content in K326 cells was significantly higher under P deficiency but little affected in Oxford. It is suggested that alternative respiratory pathway may be associated with tolerance of tobacco cells to P deficiency and may play a role in scavenging reactive oxygen species.

Purification and properties of Bacillus subtilis SA-22 endo-1, 4-beta-D-mannanase.

beta-mannanase (EC 3.2.1.78) from Bacillus subtilis SA-22 was purified successively by ammonium sulfate precipitation, hydroxyapatite chromatography, Sephadex G-75 gel filtration and DEAE-52 anion-exchange chromatography. Through these steps, the enzyme was concentrated 30.75-fold with a recovery rate of 23.43%, with a specific activity of 34780.56 u/mg. Molecular weight of the enzyme was determined to be 38 kD by SDS-PAGE and 34 kD by gel filtration. The results revealed that the optimal pH value for the enzyme was 6.5 and the optimal temperature was 70 degrees C. The enzyme is stable between pH 5 to 10. The enzyme remained most of its activity after a treatment of 4 h at 50 degrees C, but lost 25% of activity at 60 degrees C for 4 h, lost 50% of activity at 70 degrees C for 3 h. The enzyme activity was strongly inhibited by Hg2+. The Michaelis constants (Km) were measured as 11.30 mg/mL for locust bean gum and 4.76 mg/mL for konjac powder, while Vmax for these two polysaccharides were 188.68 (micromol x mL(-1) x min(-1)) and 114.94 (micromol x mL(-1) x min(-1)), respectively.