Orchid cloning, also known as micropropagation, is a sophisticated laboratory technique that creates an exact genetic copy of a parent plant. This process begins with a tiny piece of tissue and results in a large number of identical plantlets. The primary goal is the rapid, mass production of specific, highly desirable orchid varieties. Cloning award-winning or rare specimens ensures the preservation of their unique flower color, shape, and growth habits. This technique is the most advanced method in orchid horticulture, meeting commercial demand and supporting conservation efforts.
Differentiating Cloning From Other Propagation
True cloning, or meristem culture, differs significantly from common asexual propagation methods used by home growers. Vegetative division involves physically splitting a mature, multi-growth orchid, such as a Cattleya or Cymbidium, into smaller sections. Each section must contain enough pseudobulbs and an active growing point to survive. This method is slow and yields only a few new plants per parent.
Another asexual method is the formation of keikis, small plantlets that develop spontaneously on the flower spikes or canes of certain orchids, like Phalaenopsis and Dendrobium. While these offshoots are genetic duplicates, their production is unreliable and limited in number. Meristem culture, in contrast, is a precise, high-volume process performed under sterile conditions, yielding hundreds to thousands of clones from a single starting tissue.
The Scientific Process of Meristem Culture
The process begins with selecting the explant, the tiny piece of tissue used to initiate the culture. The preferred explant is the apical meristem, or shoot tip, which is the actively dividing tissue found at the growing point of a stem or pseudobulb. This tissue is chosen because it is often free of systemic viruses. Isolating this minute dome of cells requires specialized tools and precision.
The excised explant must undergo rigorous surface sterilization to eliminate all contaminants, especially fungal and bacterial spores. Sterilization often involves immersing the tissue in a dilute solution of commercial bleach, followed by sterile water rinses. This step is necessary because any remaining microorganism will rapidly destroy the delicate plant tissue in the nutrient-rich environment.
The sterile tissue is then placed onto a specialized nutrient medium, typically a solidified gel containing agar. This medium is formulated with mineral salts, vitamins, and a sugar source, such as sucrose, since the explant cannot yet photosynthesize. The medium also contains plant growth regulators, specifically a high ratio of cytokinins, like Benzylaminopurine (BAP), to promote cell division.
Within the sterile flask, the explant develops into a Protocorm-Like Body (PLB), a small, undifferentiated mass of tissue resembling an orchid seed embryo. These protocorms are repeatedly sectioned and transferred to fresh multiplication media, where the high cytokinin concentration encourages proliferation into many more PLBs. In commercial labs, this multiplication phase is sometimes enhanced by placing the PLBs in a liquid medium agitated on a shaker table.
After sufficient multiplication, the PLBs are moved to a rooting medium containing a lower concentration of cytokinins and a higher ratio of an auxin, such as Naphthalene Acetic Acid (NAA). This shift in hormone balance signals the tissue to stop proliferating and begin differentiating into distinct shoots and roots. The plantlets grow within the flask until they reach about one to two inches in height with established root systems, ready for the final, non-sterile stage.
Acclimation and Transplanting Cloned Plantlets
The process of moving plantlets from the sterile flask to the open air is known as deflasking or hardening off. Plantlets grown in the laboratory exist in nearly 100% humidity and rely entirely on the culture media for nutrition. The first step involves carefully removing the plantlets and gently washing the agar media remnants from their roots. Remaining media can become a food source for damaging fungi and bacteria in the non-sterile environment.
The newly deflasked plantlets are extremely delicate and prone to desiccation because their leaf cuticles are not yet fully developed. Therefore, the acclimation process must be gradual, starting with a protected environment that mimics the flask’s high humidity. Placing the plantlets in a closed terrarium or under a humidity dome is a common technique, providing a moisture level near 80 to 90 percent.
The initial potting medium must be fine and retain moisture without becoming soggy. Ideal materials include fine-grade orchid bark, chopped sphagnum moss, or a blend of both. The tiny plantlets are potted individually and kept in a warm location with bright, indirect light. Over several weeks, the humidity is slowly reduced by gradually opening the dome or lid, allowing the plantlets to adjust to normal growing conditions.