Dear Andreas Bernreiter;

Most of the above-mentioned natural extracts, containing primary products important for metabolism, development and growth. These vital plant compounds are sugars, amino acids as well as some natural hormones. Therefore, it is expected when using of such extracts as a cheap source for stimulates plant tissue growth, it will be given a positive result. This turn to researchers in many developing countries, and this is to overcome the financial problems of funding,

And try to get close to the results obtained by the use of specific compounds for stimulating growth. So, they can help their countries, and find alternative methods.

Because the fundamentals of scientific research is to get the results can be replicated when using the same conditions (reproducable). Because these natural extracts can not get the same chemical content at 100% at any time. So, When be used in any trial, the expected results of the experiment will not be 100% of the results of the original research trial.

From the above, we conclude that most of the research of this kind, do not have the strength to be admitted to the high impact factor journals.

Finally, Here are some research in this area

http://pcp.oxfordjournals.org/content/23/7/1205.abstract

http://hortsci.ashspublications.org/content/45/12/1848.full

http://www.actahort.org/books/764/764_33.htm

http://link.springer.com/article/10.1007%2Fs12892-013-0038-1

https://docs.google.com/viewer?url=https%3A%2F%2Ftspace.library.utoronto.ca%2Fbitstream%2F1807%2F4125%2F1%2Fjb04048.pdf

I strongly agree with Osman.

I am doing research with natural extracts and their influence on plant growth and development.

You can refer the following articles or references cited in those articles.

1. "Effect of seaweed liquid extracts and plant growth regulators on in vitro mass propagation of brinjal (Solanum melongena L.) through hypocotyl and leaf disc explants" - Used seaweed extracts.

2. " Direct plant regeneration from in vitro-derived shoot apical meristems of finger millet (Eleusine coracana (L.) Gaertn.)" - Used casein, proline and glycine additives for improving regeneration.

Thanking you.

You will find a lot of information on organic complex additives to nutrient media in the orchid literature. They have been used historically, and are still in use for germinating orchids, but also in micro-propagation. Many attempts have been made to replace these additives with clearly defined cocktails of pure organic substances (vitamins, amino acids, hormones,etc.), but very often without the same results. I don not have specific references at hand now, but you will surely find information in the papers and books, written or edited by Dr. Joseph Arditti. Try also The website of Malmgrem on germinating temperate terrestrial orchids, using additives such as pineapple juice, potato, turnip, etc.

there  will be so many information on organic complex additive to basal media and its very old time to used this type of substance or also commonly used in orchid germination in coconut milk or water. 

And  also used coconut milk ms media in bamboo tissue culture.