you are right. I've tried to implicate the complexity of the researches in this field. For the beginers, I offer BA and NAA combination first. Not BA and IAA...

But I cant explain it exactly Why? and there seems a big gap in physiological roles of the synergist effects of certain PGR combinations and concentrations in protocols.

Now, this is a very subjective issue. First, the response of plants towards PGR treatments depends highly on the type of plants itself. Different plants show different responses. It is also important to know the right concentrations of PGR that is suitable to enhance the quality of the plant culture. In my situation, after performing a series of optimization with cytokinins I realised that my plant cultures perform so much better in media without PGR. It is difficult to explain :(

Hi, thanks for the very interestiong topic. I think that combination of growth regulators (auxin and cytokinin) largely dependent from internal hormones metabolism in the certian species, from status of intial tissue, and, in many case, from non-hormonal supplementes in the culture medium. Namely, in many cases stress-factors have a dramatical effect on plant reaction to auxin and cytokinin. In my hand in many case Murashige and Skoog medoium is far from optimal for induction of morphogenic process.

in addition to Pasternak submission, Skoog devoleped another medium with Linsmaier called Linsmaier skoog Medium 2 years after MS. They indicated LS was better than MS.

Here is LS medium: http://www.phytotechlab.com/pdf/msmediap.pdf. However, LS does not solve the MS medium problem: very high nitrogen, low phosphate, very low Cu and very high Zn. MS or LS medium suitable mainly for induction of unorganized growth (tobacco callus, for what MS medium has been design) , but not very suitable for plant morphogenesis. When we use different hormones combination, we can partially overcome some of the effect coming from non-optimality of MS medium.

actually I agree with you. Some vitamins not included in LS. but I have tried LS in comparision to MS, longevity of the cultures was better than that of MS in some digitalis species. Of course this can not be all. internal and external PGR migh affect the morphogeny. In many PTC journal, discussions are not enough to mention these effects occuring at the background. Therefore, I do not believe tissue culture is a science, it's just a method...

I do not agree with you: the main problem is unsufficeint discussion in PTC journal. If we consider carefully initial stage of explants (in the term of cell status, chromatin packing etc), intial hormone distribution in explants we have used, at least phenotypical properties of the cultivar we have used, we can find strong regularities in the process of plant regeneration, growth etc, what, of course, dependent from plant species. In many cases micro and macronutrients significantly modified metabolism of internal hormones. I will try to summarize all these points soon.

Of course, Tissue culture is not a special science, it is technique but they based on plant physiology and all process, independent form species, have a high regularity. Actually, all process dependent mainly on internal phytyhormones metabolism, external one only modulated internal one. For example, morphogenesis (shoots or root induction, formation of adventives buds etc.) were dependent from gradient of plant hormone auxin.

Sure, it must base on physiology as you claimed "all process dependent mainly on internal phytyhormones metabolism, external one only modulated internal one. For example, morphogenesis (shoots or root induction, formation of adventives buds etc.) were dependent from gradient of plant hormone auxin" BUT, that's why I prefer the term of Methodolgy only as an alternative technique for breeding, since discussions are turning around same words. every plant species are unique, and certain protocols are necessary for each regeneration system, In my case, IAA is effective in rooting in many species I tried, but not NAA. However, NAA is effective when combined with BA for callusing (somebryo formation etc) but not IAA. what sort of mechanism take place for the selecetivity of the compunds? Interestingly, nobody can answer easily because as I said every plant species are unique. How long do we all repeat internal and external phtohormone mechanism etc...?, what sort of strategy should be proposed to have such general rules for plant regeneration system?

I will put such strategy to my web site (http://pasternak.cu.cc), Unfortunately, now there is a problem with hosting, I will try to solve it next week. Basically, you need to induce so-called stem cell (de-differentiated) by action of auxin and stress. You need to consider initial stage of explants (ploidy level, differentiation level, ability to induced auxin biosynthesis, etc). Of course, different plant species have different level of differentiation. For example, cereals demonstrated very strong gradients along leaf from base in the term of chromatin condensation, cell cycle exit, that's why they have some difficulties in culture. However, you can overcome majority of them!

Congratulations. your web-site seems very promissing, and this topic addresses you to solve problems upto some extent...

Hi, Buhara, I still did not find time to insert models to my website, I will do this next week. Very briefly, you should consider intail differentiation status of your materail. For the clonal propagation you do not need require cells re-programming, only activation of pre-existing potentail buds, whcih already de-differentiate and have potentail for auxin/cytokinin production even on hormone-free medium. In the case if you use differentiation explants like leaf, you make a cells re-programming, whcih require a lot extrenal hormines. You need to consider differentiation status of each cells files in your explants: in some plant species like cereals, differentiation occurred to fast and you cant got cells reprogramming with any hoprmones. For the cells re-programming, it is a general rule, that you need at the first stage induce chromatin remodelling to made cells competent to cells division by relatively high auxin concehtration. However, once cells made reprogramming, continuos high auxin will lead to dormancy in un-differentiated stage. From this cells you can easy induce somatic embryogenesis by lowering axuin and increasing cytokinin. I hope this will at least little calrify the mechanism. I will update my website next week. Good luck!

As you you know, there is a big gap for the understanding of the mechanism... another problem in tissue culture, it cannot be generalized entire plant groups (i.e species)... Is there any difference between your (Dr. Pasternak) considereation and competence-determination theory ?