Tuesday, March 11, 2008

Plants; In and Out of the Water


Most aquarium plants can grow either what we call submerged, which is totally under water, or what we call emmersed which is when only the roots and bottom portion of the plant grows in water. What you may not know is many aquarium plants are grown purposely emmersed by commercial growers to attain quicker and larger growth. Although these plants are true aquatic, they require some time to adapt to growing underwater.

Most will adapt fairly quickly, but may change their leaf structure: shape and size, dramatically. Aquatic plants have a very highly developed system of air cavities or canals. It runs through the entire plant, from the leaves to the outermost tips, and enables the plant to maintain buoyancy in the water. Because the water supports the plants, their stems and leaves have far less supporting tissue or fibers than those of land plants, so when growing out of the water, or even floating, the leaves and stems become much thicker or wider. When under water, the new growth from these thick stems will be much thinner.
Parrots feather is one example of this. As a bog plant it has thick stems with short, pinnate leaves that are close together. Submersed, that same plant will grow out with very thin, wispy stems and finely, feathery pinnate leaves. The old thick portion of the stem will lose all its leaves and can be simply cut off. Some plants will shed off their leaves and grow out new ones before growing underwater, such as echinodorus, (sword plants). Cryptocorynes in the wild are accustomed to waters continually rising and lowering, but will only flower out of the water. Many species will also grow quicker emmersed than submerged. When grown on a wet rock, or in an inch of water, Java moss actually looks like real moss, not the long, hair like strands it becomes underwater. Pennywort becomes gigantic out of the water!
The ability of many aquarium plants to adapt depends either on their ability to absorb nutrients through their leaves underwater, or from their roots. Cryptocorynes and sword plants can not absorb nutrients through their leaves and in order to adapt must have a nutrient rich bottom.
Not all emergent plants can adapt to being submersed. These are commonly referred to as bog, marsh, or marginal plants. To the Aquarius these are not considered true aquatic, and are not desirable for the aquarium since they will only live for a few weeks. They are however ideal for either terrariums or ponds.
So when you order plants by mail dont be surprised if they may look different than the pictures you have seen, or if they begin to change in appearance, and make sure the plants you buy are true aquatic!by Robert Paul H.

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