Commercial Floriculture

Propagation of orchids

SYMBIOSIS:
• There is a peculiar interdependency between orchids and fungi.
• A brief knowledge of this ‘mycorrhizal relationship’ is very necessary to understand the procedures of orchid seed germination.
• There have been developed two distinct and basic methods of germination based on this knowledge.
• In the first it is assumed that the presence of the fungus is necessary for successful germination. The fungus is isolated, grown in sterilized culture sand then, when fully developed in the medium, orchids are sown. This is a time consuming method which is hardly ever used today.
• Generally the second, the asymbiotic method is applied. Here the growing medium is enriched by mineral nutrients which provide the plant with basically the same substances as the fungus.
• A high degree of sterility, both of the sowing media and the seed is necessary. There are many new recipes for suitable germinating media. To mention a few are Burgeff, knudson C. Vacin and Went, Nitsch, Murashige and skoog, etc.
• Recently another vegetative reproduction method, meristem culture, has gained importance.
• The process is technically very complicated and demanding and since it requires a laboratory to be carried out successfully.
• However, mristem propagation has only been achieved, to a commercially acceptable standard for Cattleya, Cymbidium, Calanthe, Dendrobium, Miltonia, Odontoglossum, Oncidium, Zygopetalum and Huybrids.
• Plants produced by this method, when young are known as mericlones. Here the meristems are transferred to a culture medium where they can be subdivided and an unlimited number of new plants raised.

METHODS OF PROPAGATION
CONVENTIONAL METHODS
I. Monopodial orchids

A . Stem cuttings
B . Flower stalk cuttings
C . Layering

II .Sympodial orchids

A . Divisions
B. Offshoots
C . Back bulbs

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Micropropagation of Orchids
• The modern methods of propagation have brought orchid cultivation on par with other commercial crops.
  
• In-vitro seed culture:

  • Orchid seeds are extremely small (80-130 Mm wide and 410-560 Mm long) and usually undifferentiated.
  • They produced in large numbers ranging from 1300 to 5 lakh/capsule.
  • Each seed contains an undifferentiated embryo composed of 80-100 cells without any functional endosperm.
  • Under natural conditions the orchid seeds germinate in association with fungus (Mycorrhiza).

Fertilizer Application
• According to some workers Ammonium nitrate is the best nitrogen source for early germination and protocorm formation. After the roots and leaves are formed the protocorms prefer nitrate for their continued growth.

  • In their natural habitats, orchids grow on no special nutrients, depending only on what they could absorb from decaying tree bark and the atmosphere.
  • A synthetic inorganic fertilizer, equally balanced in,

    • NPK 17:17:17 or 20:20:20, dissolved in water @1-5g per litre applied once or twice a week gives satisfactory results.
    • To promote flowering, a higher proportion of phosphorus and potassium such as 10:20:20 is helpful.
      

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