Dendrobium - Science topic

I believe Orchids are an exception to many a Groningse moestuin/norm. Orchids flourish with a lack of attention.

Roman Bohdan Hołyński gave the answer in a nutshell. The bad thing about the monophyly requirement is, that by and large it has become a dogma. Any dogmatic approach to a scientific question is in itself suspect.

Be aware of the logical conflict in the monophyly concept that has been pointed out by Roman Bohdan Hołyński (an by others before him). And then, ask yourself, non-dogmatically, what do you wish to achieve. The monophyly concept is relevant for classification, and it is valuable as a method to assess the "value" of any proposed classification. Nomenclature is an entirely different concept, and serves communication. We have grown to accept that the names of organisms must reflect their classification; but when accepting this becomes axiomatic, it reflects negatively on the usefulness of names as information vectors. When we wish to address a taxon that is worth while being recognized, because it is recognizable and we want to communicate about it, it is not primarily relevant that the taxon be monophyletic. Changing names each time a new classification hypothesis is proposed impairs the usefulness of names as information vectors and, in the long term, is contra-productive.

Even when one is reluctant to abandon full congruence between classification and nomenclature, one should bear in mind that translation of the first into the second is not a strait-jacket but leaves options; and it is the duty of responsible biologists to choose the option that is least disruptive with respect to familiar usage, and is most robust under the variation in classifications, or phylogenies, that are likely, if not certain, to occur in the future.

Hi Paromik,

I have a large orchid collection and grow several of the deciduous species in genus Dendrobium section Dendrobium, including Den. aphyllum. My guess is that the genetic basis for their deciduous character is the same as that for other deciduous plants (i.e stress cues such as lack of moisture, change in temperature, light levels and day length will induce senescence of the leaves and then leaf drop via their abscission layer, which is clearly defined in Dendrobium leaves). BTW, I'm a structural biologist and not a plant scientist, but a quick search showed me that your question doesn't seem to have been clearly answered for even well-studied plant species (but don't take my word for this, I'm not an expert in this field and I did not carry out an in-depth search for papers on the subject).

I guess that you would need to collect leaf samples during different seasons and study their mRNA and microRNA pools that might indicate changes in gene expression.

Here's what I know from growing these plants for many years. The deciduous species in this section live in areas with clearly defined seasons and they shed their leaves during the dry season, which coincides with winter in the northern hemisphere. A combination of environmental conditions results in the loss of leaves:

The most important cue for loosing their leaves seems to be the lack of rain. Even if you provide all other cues, they will not drop their leaves as long as they have enough moisture. Flowering is only triggered by a combination of all of the above factors followed by an increase in day length and temperature in spring. Lack of any of the aforementioned factors during the rest period results in very poor or no flowering. In particular, excess moisture that inhibits leaf loss during the dry season will result in lush growth in spring and in the production of keikis (daughter plantlets) instead of flowers from the nodes where the flowers should emerge. Even a plant that has been provided with all the right environmental cues during the dry season and lost all its leaves will not flower properly if it receives too much water in early spring just before the flowers start forming. This seems to be a survival mechanism whereby these plants prefer to use the extra moisture to grow into larger plants instead of for producing flowers. I assume that the reason for this is that larger plants stand a better chance of surviving a really harsh dry season in the future.

I hope this helps.

TDZ is basically defoliant when used on plants growing in natural environment.  The in vitro grown explants are grown in a protected environment to the extent that they get glucose/ sucrose as readily available carbon source.  The metabolism of the tissue grown in vitro is entirely different (that is why the plant-lets need to be acclimatized when they are transferred to soil).  Therefore the chemicals which are used in vitro act differently than in vivo conditions.  I would like to mention my observation  when I use TDZ is that  it gives good response when 3 to 4 % sucrose is added. 

Will this help? http://www.plosone.org/article/fetchObject.action?uri=info:doi/10.1371/journal.pone.0097364&representation=PDF

Besides, won't you expect the majority of cells (>80%) in interphase at any given time? Unless you arrest the cells with nocodazole, that is! 

According to Lavarack, "to grow and flower well, this species [D. crepidatum] must be given intermediate to cool conditions with a dry resting period in winter and early spring, During this period watering should be much reduced with the plants drying out and remaining dry for several days between waterings... bright sunlight or light shade are recommended." The same goes for nobile. The best is to place the plants in bright conditions and do not water! only mist from time to time to keep the pseudobulbs from shriveling. The will produce buds from the nodes on the stems and only then can you give water in small quantities. Otherwise you risk getting only keikis (small plantlets) from the nodes. Lavzrak, Harris, Stocker : Dendrobium and its relatives, Timber Press.

Hi Paromik, we have not tried apple juice before and so we cannot give you any advice. The best way is still to use a defined medium formulation (with known cytokinins) to induce in vitro flowering such that your new method will be reproducible. If you cannot achieve in vitro flowering using defined medium for your particular Dendrobium species, this is where the young and green coconuts' water (undefined medium), will be great back-up plan. Alternatively, if you have the budget, you can measure the cytokinins, auxins and gibberellins (using either LCMS or ELISA) of 100 green coconuts, and then freeze these coconut water collected.

ISSR analysis could be carried out together with RAPD marker to get clear genetic difference with in short time

Agus, here are our past journal articles about orchids (including Dendrobium) used in traditional medicine.

For this area of ethnobotany, it is better to refer to books.

There are great coverage of this area by Prof Joseph Arditti in his excellent book "Fundamentals of orchid biology", or his review series (Orchid biology: Reviews and Perspectives":

Good luck to your research. John (Singapore)

There is no listing for this species in Tropicos. There is a Coelogyne corymbosa but it is unlikely that it would be confused with a Dendrobium.