Oglesby Plants International

Acclimation of Tissue Cultured Plantlets

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Tissue cultured plantlets require special attention during the acclimation process from the laboratory to the greenhouse in order to avoid losses and ensure crop uniformity. As the laboratory is a relatively stress free environment, the plants need to be slowly phased into greenhouse conditions.

Incoming stage II microcuttings need relatively immediate attention, while stage III plants can be held in a controlled environment for a few days without diminishing quality. As plants are coming from a relatively sterile environment, worker and workplace sanitation is essential. Disinfect all tools, containers and work areas routinely.

Media: Most growers prefer a peat-based medium. Use 70 to 80 % quality milled peat amended with perlite, vermiculite, or bark. Avoid coarse, large particles if using bark. Adjust pH to 5.8 to 6.1 with incorporated dolomitic limestone. Incorporate a low concentration of slow release fertilizer including trace elements. Premoisten the medium before filling trays.

Keep in mind that plants in the laboratory are grown under only 200 to 600fc. (2.2-6.5 klux) and are kept very close to a uniform 78F (25C) degrees. Thus while planting and during acclimation protect the plants from the brighter greenhouse environment and extreme temperatures. Stage III plants are rooted in lab media containing high concentrations of sugar. This media should be gently washed or shaken off to prevent the growth of undesirable microorganisms once planted. Use a dibble when planting. Forceps with a felt padding can be used to aid in planting very small microcuttings. Place plantlets just deep enough to anchor them into the medium. Use a spray bottle of water to mist the plantlets during handling. When a tray is completely planted, water in thoroughly but gently with a mild solution of 20-20-20 (or similar analysis) at 100 to 150 ppm.

Plantlets directly from the lab have no cuticle and will require high humidity to survive. Use a mist or fog system to prevent desiccation. Increase the mist interval gradually during acclimation. An alternative is to cover the trays with clear lids, or a layer of polyethylene film or cheesecloth. Be sure to provide ventilation as necessary to prevent heat buildup. Additional shading should be provided. Double the light levels every one to two weeks until plants are acclimated to their normal light requirements.

Do not allow the medium to become waterlogged. A regular fungicide program should prevent losses from root and stem rot diseases. The initial environment should be kept at 80 to 85F (26-30C) day and 70 to 75F (21-24C) nights. Bottom heat will help induce rooting.