Garden Water Plants are Botanical Miracles
Garden Water Plants are Botanical Miracles
Water plants are quite astonishing in their ability to do unusual things. It is interesting to discover that, in fact, these plants do not derive directly from ancient plants that also grew in water. They were all previously land plants that have adapted to life in water.
The development of increasingly large numbers of plant species on land caused great competition for survival which some plants avoided by adapting to life in wet areas. Gradual mutation and change enabled them to diversify and penetrate wetter habitats until they ended up adapting entirely to life in water. This evolution can be seen quite clearly in the example of amphibious bistort. Unlike many other garden, it has not entirely given up life on land, but is able to grow as a water or land version depending on its position in the environment. This plant is, therefore, referred to as an amphibian.
- They learned to float.
- They are able to perform an exchange of carbon dioxide and oxygen underwater.
- They are able to absorb nutrients not only through their roots but also through their leaves directly from water.
- Their leaves are not equipped with a water-impermeable wax layer as this would hinder any kind of exchange of gases from the surrounding water.
- Flowering, pollination and the distribution of seed are all possible underwater.
Propagation without flowers
Propagation from seed is a fairly unfavourable method for flowering plants that live underwater. A deficiency in oxygen supply on the floor of the pond will often cause the seeds to die, which is why flowering plants in a pond usually propagate by means of rhizomes and the branching of rhizomes. It also means that lots of water plants of one species always grow together in dense groups, while in the case of land plants which propagate from seed, many very different species can grow in a small space. Propagation by means of rhizomes also occurs very often among non-flowering water plants. For example, the Chara species of algae form a dense underwater carpet which often completely obscures the bottoms of cleaner, light-permeable waters.
Some water plants, like common bladderwort and hornwort species, no longer form any kind of roots. These plants are very successful cleaners of the water in garden ponds, as they absorb nutrients dissolved in the water through their leaves alone. In this way, they use up more nutrients from pond water than plants that root in the bottom. Hornwort is only present in water which contains sufficient dissolved nutrients for its nourishment. Common bladderwort will also colonize clear water with low quantities of dissolved nutrients as it is able to catch and digest small creatures, such as water-fleas, as a supplement to its diet. This carnivorous plant has adapted some of its leaves into small bladders with a low internal pressure. Fine hairs situated around the surface “trapdoor” entrance of this bladder react to the touch of these minute water creatures by opening suddenly. The influx of water pulls the water-flea into the bladder, the trapdoor closes and the creature is digested.
Nourishment from the air
Nitrogen is a vital element of nutrition among all plants. Most water plants rely on nitrogen compounds dissolved in the water and on the pond floor. Blue algae, however, are able to absorb nitrogen directly from the air. Eventually, through various biological processes of decay and redistribution, this nitrogen will be made available to all the plants in the pond.
These can be seen in hornwort, for example. Underwater flowers are actually fairly inconspicuous as they do not need to attract insects for pollination purposes as land flowers do with their splendid, colourful and scented petals and other parts. As a rule, water insects are carnivorous, preying on other insects and water creatures, and would, therefore, not collect pollen from flowers.
Some underwater plants form small buds in order to survive the winter. These buds drop off, are buried in the mud at the bottom of the pond and are thus protected from freezing to death. These overwintering buds come to life again in the spring to produce new plants of common bladderwort, frog bit or water soldier, for example. The overwintering buds are small and inconspicuous so, when clearing out dead matter from the bottom of the pond in autumn, you must take care that these buds are not damaged.