Tissue Culture Finishing

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- [Sinclair] A number of greenhouse propagation companies are using tissue culture or micropropagation as a production method for many new plant introductions.

This method is employed in botany and horticulture, but the major reason greenhouse companies are producing plants using this technology is the rapid propagation of specific clones.

There are four main stages of tissue culture, but here we will be concentrating on Stage IV, the acclimatization of plants from the lab into the real world.

Plants growing in the laboratory are in sealed vessels, in agar or Phytagel media.

These media contain all the necessary elements for proper plant growth.

And here you can see the major and minor salts that are used in the formulation of this medium, as well as the vitamins and hormones used for in vitro production.

The development of media for many species and cultivars enables growers to produce high-quality crops of perennials and annuals.

For example, many Echinacea selections have made rapid entry into the horticultural market by virtue of successful tissue culture and have been quite well received by consumers.

Tiarella is another group that has become more successful in production using tissue culture.

While running types can be produced by stem cutting, clump forming selections are produced using tissue culture.

The rapid growth of Huechera selections that has been possible due to tissue culture and selections like Heuchera Forever Purple would have not been possible without using this propagation method.

Heucherella, created by crossing Tiarella and Heuchera, have been propagated successfully in tissue culture as well.

These plants have become very popular in gardens with shady settings.

Daylilies or Hemerocallis are one of the most popular garden plants and are grown in most US states.

Producing daylilies by conventional division may take several years to make up stock.

But with tissue culture, that development time is substantially reduced for bringing a new selection to the market.

Gerber daisies are also produced overseas and propagated by tissue culture, reducing the chance that disease will be passed on from the propagator to the grower.

Since tissue culture occurs in sealed vessels, proper acclimatization must take place to ensure the post-lab production phase is successful.

Leaves are without cuticle in the lab phase and newly formed leaves with cuticle need to be produced in the greenhouse.

Another aspect of this altered morphology is that the roots are poorly developed in the lab and unsuberized.

New roots will need to be produced on the plant in the greenhouse environment.

Stomata are generally concentrated on greater numbers on the underside of a leaf and are poorly functioning or not functioning at all.

Newly formed leaf tissue will also produce fully functioning stomata which will facilitate proper gas exchange for the plant.

Handling a shipment of tissue cultured plants is an important step in the production process.

Boxes should be unpacked promptly and the contents inspected for shipping issues and plant quality.

Styrofoam liners inside the boxes will help to protect the shipments from temperature extremes and heat or cold packs are also used for temperature security during shipping.

The open shipment should be placed in a suitable temperature, 65 to 80 degrees Fahrenheit would be optimum, and in low light levels prior to transplanting.

Inspection of the contents of these tubs is critical.

Diseased or damaged in transit will need to be claimed with the lab.

And these tubs have to be transferred to a suitable carrying container for greenhouse production.

Once the tub has been opened, it should be planted promptly as delays at this point will cause plant desiccation.

Transplanting by hand is frequently used by propagation companies.

And using a bamboo dibber stick, the plantlets are put into the potting media.

This has proven to be a successful method.

Sorting the plantlets by size when sticking is a good method for increasing the uniformity of the finished flats.

And the worker here is putting the larger plants in one tray on the left and the medium size plants into the tray on the right.

This Hardy Geranium Rozanne is a very popular perennial selection and this company is producing close to 10,000 per month.

Looking over a recently transplanted bench of Geranium Rozanne shows the initial production results.

Plantlets will still need several weeks in the mist system and some additional growing on time before they're ready to ship to another grower.

Carex pensylvanica, a very popular landscape plant, has come to this grower as a multi-shoot clump from the lab.

This method significantly reduces the growing time and increases the uniformity of the plant.

Woody and herbaceous species and cultivars can be produced by tissue culture.

And you can see here, apple, rhododendron, mountain laurel, orchids, Heucherella, and African violet.

It is also possible to produce pitcher plants by tissue culture, but they have a very long developmental period both in the lab and in the greenhouse.

Some plants such as Heuchera Snow Angel perform very badly in vitro, yielding a predominance of green and albino forms.

If a shipment of tissue culture can't be planted immediately, it is possible to hold the plantlets for a short period.

Acclimatization in the greenhouse is important.

Mist, light, and temperature need to be suitable.

Newly transplanted micro cuttings will take six to eight weeks development time and finished plants are ready to ship out like these Heuchera Tiramisu.

Tiarella like this oak leaf variety will also take six to eight weeks.

Unless temperatures are above 80 degrees, then the growth would slow.

Fertilization will vary by species, but 75 to 120 parts per million nitrogen would be optimum using 21-05-20 or 13-2-13.

Plant development time may take from six to eight weeks at 400 to 1,000 foot candles with a temperature at 55 to 80 degrees Fahrenheit.

Today, systems are available for automatic transplanting.

Plants are grown in special trays and then transplanted by these automatic transplant machines.

This transplanter was made in Australia and is very efficient in moving the plants from the lab tray into the flat potting media.

Grippers gently grab the plantlets from the tray and move it to the flats.

These machines also eliminate potential contamination from the workers handling the plants since seven plants are moved by the grippers at the same time and the robotic arms adjust the space from tray to flat.

Not only will the system increase production, but it will help with plant uniformity in the flat.

Robotic or mechanized transplanting is the way of the future and large scale operations can attain greater numbers and improve crop quality using this production method.

Here at TERRA NOVA Nurseries in Oregon, tissue cultured plants are ready to ship.

Problems with tissue culture does occur and these should be claimed with the laboratory.

Here you can see plants that are undersized and plants with brown roots.

For this reason, it is important to have a good relationship with the lab.

Another example of problems would be discoloration or shipments that were shaken up.

Contamination can also be biological, caused by fungi or bacteria.

And hyperhydricity occurs when the plants are grown improperly in the laboratory.

Once the crop has completed the mist phase and has moved into the finish zone in the greenhouse, it can be watered as with any other flat grown plant material.

Thorough irrigation of the flats is the desired approach while taking care not to overwater the crop.

For more information, please contact the Penn State Extension Greenhouse Team.

Thank you very much.