@ Arvind Kumar Goyal,

Some of the techniques that can be used in angiosperm taxonomy are:

1) Taxonomy based on morphological characters.

2) Cytotaxonomy based on cytological data.

3) Chemotaxonomy based on biochemical data.

4) Taxonomy based on molecular markers.

5) Taxonomy based on DNA sequencing.

If the plant species is easily identifiable on the basis of morphology, no need to proceed on to other techniques. If not, one can go for Cytotaxonomy. Cytotaxonomy can suggest that two species under consideration are morphotypes or cytotypes or both. Biochemical technique can be used if earlier techniques have not solved the problem. Molecular markers and DNA sequencing are the latest techniques in angiosperm taxonomy.

Regards

I should note that at the moment, due to the high resolution chemical analysis methods, virtually disappeared marker compounds that would be typical for this or that group of plants. In this connection Chemotaxonomy not answer the question of taxonomists.

There are a lot of different techniques which are used for angiosperm taxonomy and also phylogeny. To these techniques you need more or less of specific equipmet and knownedge. In many cases some simpe methods is enough, but to make a precise taxonomy in most cases you must join different approaches to get consensus result

1) morphologial and micromorphological features

2) so called chemotaxonomy - biochemical features (i.e. secondary metabolites, proteins, some specific products or pathways and many others can be used in such way)

3)taxonomy by genetic different molecular genetic markers (there are thousands of different markers from all genomes of plant cell used in taxonomy and phylogeny - for example rDNA, chloroplast genes and spacers, mitochondial genes)

4) so called DNA-fingerprinting (include AFLP, RFLP, RAPD and many other techniques)

5) full genome sequencing (this approuch never been used in taxonomy completely, but helpful in many cases)

6) studuing differences in transcriptomes

It is not full list of all techniques, it'sonly very brief review of it.

Dear Arvind,

I agree with Andrii Tarieiev in his first paragraph. If you really know your group of plants you can start a reliable taxonomy. It means that all the techniques are appropriate for taxonomy, but some of them more appropriate than others for different groups. Later, there are statistical tools that can help you choose the most appropriate and reduce the number of measurements.

Have a Happy New Year!

To study the modern trends in taxonomy we must go through the history of classification and how this branch has developed with the development of peoples, instruments and techniques. We must keep in our minds that taxonomy today is a reflection of the past, meanwhile the systems of classification reflect both needs, level of knowledge, philosophical concepts and available technology of each historical period. Therefore, a holistic approach towards more objective taxonomic inference will be a combination of traditional as well as modern methods. Data from the following fields of study can be used in achieving a holistic relationship of angiosperms:

1) All aspects of plant morphology viz. micro-morphology, palynology, anatomy, embryology, cytology etc. Despite the advent of many modern techniques,  morphological characters are the most important tools in the taxonomic analysis.

2) Chemo-taxonomy and serology

3) Paleobotany and phylogeny

4) Molecular analysis of DNA sequence data from the chloroplast gene rbcL and from chloroplast restriction analysis of the inverted repeat and nuclear rRNA sequencing. These data together with morphological and other data from the other tools of taxonomy have made great change in the world of taxonomy.

5) Cladistic analysis

You may be interested in the website of the Angiosperm Phylogeny Group at http://www.mobot.org/mobot/research/APweb/welcome.html . The focus is systemics & classification. I've attached what I think is the most recent paper from the group.

Nearly all known technics have been mentioned.

In my opinion, DNA sequences with other biosystematics information can help to taxonomist to better classify the taxa.

All the above trends and Techniques surely supplement the Science of Angiosperm Taxonomy. But none of them lessens the importance of Classical Taxonomy.

Arvid rightly points out two problems: obtaining empirical data and its interpretation. With the first no problem now. The main problem - in interpretation. Part of evolutionary processes is a hidden form and is not reflected in the phenotype. But hidden processes are reflected in the genome. They are pronounced in demonstration «cryptaffinal transitions». The evolutionary process is not gradual. Right supporters of the theory of punctuated equilibrium. But we can go further. Shown that the saltation is not a simple acceleration of some standard evolutionary process. In evolutionary static taxa, the «burning out» of cytosine occurs, first of all in CpG dinucleotides, while the rDNA of evolutionarily active taxa is saturated with dC, dG and CpG dinucleotides. In a long phylogenetic branch consisting of a number of successively changing evolutionarily elements, the process of saturation of rDNA with cytosine and guanine prevails above the processes «of burning out». Thus, static and saltation periods of the evolutionary process differ in the character of molecular processes in evolutionarily important elements of genome. In whole, an increase in evolutionary advance of plants at macro-evolutionary level correlates with an increase of G + C and CpG content in ITS1-5.8S-ITS2 region of rDNA. An evolutionarily active part of a phylogenetic branch is also structured and may be characterized as a two-stage cryptaffinal transition.

For details, see: «Dynamics of Chromosome Number in Long Structured Phylogenetic Branch of Monocotyledons: A General Scheme of Evolution» on my page in ResearchGate.