Wednesday, 20 March 2013

The growing mediums

The Growing Mediums 

As it was mentioned in the chapter "A little bit of Orchid science", orchids need fungi to help them grow. How does this work? Well there have been numerous research projects conducted to try and find a way of propagating orchids without needing the fungus. They have all used AGAR, a gelatinous substance with the specific nutrients and growth hormones needed for each plant to grow. It doesn't just work with orchids, there are many plants that can be propagated this way in a lab. The two being used are Mirushage & Skoog and F522. 

Mirushage & Skoog (MS) 

This growing medium was invented by Toshio Muragishe and Folke K Skoog in 1962. This happened during Murashige's extensive research to find a new plant growth regulator. The mix can be modified to suit the plant being grown. Some research undergone has shown that it is not a recomended medium for orchid growth but can be used, (J. Arditti,2008).
The standard mix found in MS medium are the following essential plant nutrients:
- Potassium
- Calcium
- Carbon
- Nitrogen
- Magnesium

and many more. These of course change depending on the plant.( R. Trigiano & Gray. D, 2010) 

The medium F522

An american company called Phto- technology Laboratories  have developed a growing medium specifically for terrestrial orchids such as the genus Dactylorhiza. It is a sucrose and Fructose specific medium that also contains the gelling agent that allows to solidify. In the mix we must also include the growth hormones needed to stimulate shoot and root growth (this replaces the fungi), (Phyto technology labroratories, 2011). The growth hormones that are present are cytokinin and auxin. The Cytokinin is what stimulates cell division, a hormone that can be found through natural sources. Auxin is what stimulates root and shoot growth after germination. (A. Perrara, 2012).
These growth hormones can be found in all types of growing mediums but they can change depending on the stage of growth. 

The BIG question

So the whole Dissertation is about this on question:

On what growing medium will the Dactylorhiza seeds have a better germination rate?

My hypothesis is that they there will be a better success of germination on the Phyto technology Laboratories F522 medium. This is because it has been produced after a number of years of research and has the necessary food source for the orchid's embryo to absorb! 

A little bit of orchid science

Orchids are very complex plants, I am sure some of you already know that some grow without soil and some grow with but before it gets to that stage, there is something about their germination that you need to know.
Orchids and fungi have a symbiotic relationship, this means that they each benefit from each other. And you ask yourself the question, “how do orchids benefit from fungi?” well here is the explanation.
From the moment the Zygot* is formed after pollination, it has to undergo a number of divisions to create the embryo. This first division happens in the whole seed creating two poles, one where growth happens, usually at the top of the seed and one that has a stalk like shape, usually this is at the bottom. This part of the seed is called the suspensor, this allows the seed to absorb and manufacture nutrients from the embryo. The only problem is, Orchid seeds have no embryo (see plate 1). So what happens now?

Orchid seeds still have suspensors in order to help the embryo absorb the necessary nutrients. But the fact that they don’t have an endosperm to hold the nutrients and necessary food sources like starch and protein like in other plants e.g. Barley (see plate 2), they rely on the fungi to get those missing food sources.
The fungi that help terrestrial orchids are called Hyphae, these are long filamented branching structures. Once they break into the Testa or seed coat, they do not cause any damage inside; instead they allow the seed to absorb the necessary nutrients to feed the embryo. The fungus penetrates the embryo through the suspensor cell, growing its hyphae in the inner embryonic cells in little coils that are called peletons. The Orchid then simply absorbs the peletons thus creating a nutrient source. When this has happened, the embryos mass increases to for a protocorm. Even when the protcorm is developing the Hyphae continue to enter the seed, though it is in larger numbers and continue to feed the plant until it produces a shoot with absorption hairs to increase root, soil and fungus contact.

It is still unknown what the fungus benefits from this relationship and it is said in some cases that the orchid is a parasite to the fungus. However the relationship between orchid and fungus continues. The orchid consumes the peletons as they are a main carbon source until chlorophyll organelles are produced, when this has happened the orchid no longer needs the peletons as it can get its carbon source from the process of photosynthesis, this can however depend on the orchid as some species only produce the organelles at a certain maturity and other species don’t produce any at all and depend entirely on the fungus, this is why in some cases they can be considered parasitic.
So, what happens when you want to grow orchids in a lab? This is where micro propagation or in vitro cultures come in and you can find the explanation for this on the next page. (The culture sheet project, 2008).

plate 1: Orchid seed Embryo: Phil Gates, 2008.
Plate 2: barley seed germination. Plant phys, 2000
Figure 1: Hyphae. toxinology, 2001 -2013. 

*Zygot: Cell formed when to gamete cells are joined after sexual reproduction. 

Wednesday, 27 February 2013

The Seeds have arrived!

When I decided that I wanted to do this for my dissertation, I needed to find some seeds. I was looking on various orchid nursery websites, I wasn't sure if I wanted to grow terrestrial or Tropical. In the end, I contacted my old mentor from Kew Gardens, where the best place to get seeds from. He replied saying as it was for my dissertation, Kew would quite happily give them to me. The seeds that I was offered were Dactylorhiza seeds. At this point I am very happy!

I had to sign a contract to ensure that I do not sell or give the orchids without the "OK" from Kew gardens, so if any of you want them, you might have to wait a while before I can give you an answer. They need to grow first though!
Once all the paper work was done (it took ages), I sent it off and, one week later, I received a parcel.....


 Here they are with the envelope, in tiny little vials! with the note sent with it!
The numbers here are the batch numbers! 

Tiny, dust like seeds waiting to be germinated.

All photos where taken by me! 
They need to be kept in the fridge until I need them! And as I am still waiting for the medium, they'll probably be there for a while!!

Tuesday, 26 February 2013

Dissertation Idea


I am a second year Horticulture student at Writtle College and we have been told to start planning our dissertation due in at the end of the third year.

I have decided to start a blog to help me log information and to share my progress with my "research".

The orchids that I will be growing are Dactylorhiza purpurella and Dactylorhiza fuschii, these are terrestrial orchids found all over the UK and Europe and some parts of the USA.

Dactylorhiza purpurella:

D. purpurella or Northern Marsh Orchid, is a perennial orchid that can get up to 45 cm when in bloom. The stems are thick and hollow, developing late March to early April. Mainly green but can have some purple tips.

When mature the plants have four to eight green, broad and lance shaped leaves (meaning they are long with a pointy tip). The leaves of this specific are normally un-spotted. The lower leaves are 16 cm long!

The flowers are violet purple with a pale throat, opening from mid May to late July. The Lip is a complex shape and is marked with deeper purple lines or spots. The upper sepal and petals will form a loose hood over the column, which contains the sexual organs. The thick, downwards pointing spur is shorter than the purple/green ovary.
The Northern Marsh Orchid is commonly pollinated by bees and bumblebees. (Kew Gardens, 2010).

D. fuchsii or Common spotted orchid has similar characteristics to D. purpurella, the only difference are the flowers. This Orchid has light purple almost white flowers, with darker purple spots on the all petals and sepals of the flower.  The leaves are the same shape as D. purpurella, and they are green and purple in the spring. (RHS, 2011).

The dissertation would be a trial with two laboratory growing mediums, one called Mirushige & Skoog and one called F522, kindly being sent to me by a company called Phyto technologies, based in Kansas, USA. Both growing mediums have different properties which I will talk about in another post and also when I have found some more information about Mirushige & Skoog and the work with orchids.