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Pollination Technique - A Primer
 
 

A Close Look at a Brassolaeliocattleya

Text by Marianna Max and Photos by Dale Borders


Figure 1
Figure 1: Brassolaeliocattleya Drumbeat 'Heritage', a showy hybrid

Pollinating an orchid is really quite simple once you know the basic flower parts and where to find them. Even relatively small-flowered orchids can be pollinated using the following method although for this illustration we will use a large specimen for clarity. The first figure shows Brassolaeliocattleya Drumbeat 'Heritage' in full bloom. These large blooms make an irresistible target for a pollinator (even though this is a hybrid!). Large showy petals and sepals that flutter in the breeze attract the pollinator's attention, in this case possibly a bee. Flowers also have unseen (at least to us) ways to guide pollinators to the target. For example, flowers may have the equivalent of "landing lights" or "runway guides" that are visible in the ultraviolet spectrum. Bees, which can see in the ultraviolet, will see very bright targets almost like a bulls-eye, but which to us appear as simple striations. A flower like this may appear very different to a bee than to us. As can be seen in Figure 2, the striations in middle of the flower point from the lip towards the center of the flower and the column which houses the sexual parts of the flower. Let's take a lesson from the bee and move in closer to take a look at the structure of the column. A close front view of the column can be seen in Figure 3.

Figure 2
Figure 2: Labellum

Figure 3
Figure 3: Column as viewed from the outside of the flower

The column is the central structure that is contiguous with the stem (pedicel) and the ovary. The petals (usually held at 2, 6 and 10 o'clock with the petal at 6 o'clock being modified into a lip or in the case of Cypripedium into a pouch) and the sepals (at 12, 4 and 8 o'clock) attach to the base of the column where it joins with the ovary. The column contains the stigma, which is the "female" sexual part of the flower and the anther, which is the "male" sexual part of the flower. In most orchids the anther is held at the front top part of the column. The anther is made up of the anther cap, which protects the pollen and sometimes positions a viscidium (sticky pad attached to the pollinia via a thread or stipe) that helps the pollen stick to the pollinator, the multiple locules which hold the pollinia, and the pollinia, which consist of pollen grains that are molded into hard and waxy or mealy, solid, compact structures. Most orchids have two, four or eight pollen masses or pollinia. No orchids have loose pollen grains. Pollinators usually encounter the pollinia when exploring the flower and these pollinia "glue" themselves to the part of the pollinator which comes into contact with them - either by being themselves sticky or via a sticky viscidium, which attaches to the pollinia via the stipe. The rostellum is a veil-like structure that bisects the column on a horizontal plane and is positioned between the pollinia in their anther housing and the sticky surface of the stigma. This can best be seen in Figure 4.

Figure 4
Figure 4: Underside of the Column

The goal of this exercise is to get the pollinia out of the anther and onto the sticky part of the stigma without losing it on the floor! I like to place the plant on a white piece of paper so that if I drop the anther or pollinia, I will have a better chance of finding it. Using the flat part of a toothpick, touch the end to the sticky fluid on the stigma. You might want to remove the lip of the flower the first time you do this so you can see what you are doing, but generally this maneuver can be accomplished "blind" by simply putting the end of the toothpick in the vicinity of the stigma and briefly touching it. This will make your toothpick sticky and make it easier to remove the pollinia from the anther. Now, simply touch the toothpick to the base of the anther cap and gently lift. This will expose the pollinia and you can touch the pollinia with the sticky part of the toothpick. Generally the pollinia will pull out of the anther cap and either the cap will remain on the column or it will fall away. Sometimes the whole assembly will come away together. If that happens it is best to put the anther in the dampened palm of your hand, and with the toothpick in the other hand (hopefully still sticky), gently touch the area where the pollen is located and pull up. This should dislodge the pollinia from the anther cap. Masdevallias are often difficult to pollinate because of their small size and the fact that the pollinia tends to stay in, and is difficult to remove, from the anther cap. For these you may need a magnifying glass and forceps.

Figure 5
Figure 5: Anther cap and Pollinia

Figure 5 shows a view of the anther resting on a sepal of the flower. The pollinia have been removed and are lying next to the anther. You can see the locules (the sack like structures) that hold the pollinia. Now it is a simple matter to pick up the pollinia with the sticky stuff that is still on the tip of your toothpick. You can simply make the same motion as you did previously when you got the tip of the toothpick sticky. This time you will carry the pollinia to the stigma. The pollinia should easily stick onto the stigma surface. Figure 6 shows the view that you will see as you bring the toothpick in towards the stigma. Notice that the anther cap is gone and the rostellum (the front edge of the stigma) is visible. If you have removed the lip, you may want to view the flower from the bottom. If you haven't removed the lip, it may be necessary to gently push the lip down to get it out of the way when you move the toothpick into position. Figure 7 shows the pollinia applied to the stigma. This is the job completed! Now the rest is up to the flower.

Figure 6
Figure 6: Column end after pollen removal

Figure 7
Figure 7: Underside of Column after Pollination

What happens in the event of a "good" pollination, i.e. one that is compatible with the plant, is that usually the stigma swells and sometimes encases the pollen. This response, which I call the pollination response, indicates that the flower is aware of the pollinia. This is a good sign but doesn't necessarily mean that the pollination will be successful. Sometimes flowers have mechanisms to avoid being self-pollinated and will not complete the process if pollen from the same plant is placed on the stigma. Often the flower will also wilt and some flowers even change color upon pollination. Over the course of the next few days, if the flower is responding appropriately to the pollen, pollen tubes will form in the stigma and grow into the ovary. These pollen tubes make a passageway for the pollen grains to find the ovum and unite the genome of the pollen with that of the ovum. In a "good" pollination, the ovary will begin to swell, usually in a matter of days. This varies amongst species but if you see the ovary swelling, you are probably on your way to growing a capsule. Even this doesn't guarantee success however, as some flowers will grow a capsule and there won't be any live embryos in the seed. This is the reason that Troy does a microscopic exam of the seed that you donate. By performing this operation he can estimate how many seeds have live embryos and can estimate how many seeds to sow for the mother flask. He can also avoid sowing seed with no live embryos and this helps to make flasking cost effective. Check out some of the seed reports here for a view of embryos.

Bad Vanda coerulea seeds     Good Vanda coerulea seeds
Bad Encyclia wendlandiana seeds     Good Encyclia brachiata seeds

You can find out more about harvesting your seed by referring to Troy's article "Capsule Drying and Seed Preparation". There are also other articles on this site discussing some of the unusual pollinations required by certain genera, please check the Index of Informational Pages.

 
 

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