Hydrophytes:
Hydrophytes:Hydrophytes are plants that live with an abundance of water available or live in an aquatic habitat. They can either be fully submerged underwater, like elodea, or have their leaves and/or flowers be out of the water, like lemna minor. By being in the presence of water all the time, adaptations to prevent water loss are not present as adaptations to handle being around water all the time. They also don’t have much gas available, carbon dioxide for photosynthesis and oxygen for respiration. Hydrophytes give homes and food to other organisms that live around the lake, sea, pond that the hydrophyte is in. (Roberts, 2011)(Jones, 2015)(Class Notes,2015) (Fieldtrip to the Hamilton Gardens) What affects the rate of transpiration in Hydrophytes?Hydrophytes have an unlimited supply of of water unless their habitat changes, this causes transpiration to not be a problem compared to xerophytes and mesophytes as they don’t have an unlimited supply of water. Even saying this, in hydrophytes light intensity, wind speed and temperature do affect the rate of transpiration because the stomata are on the top of the leaves. Light intensity affects the rate of transpiration for hydrophytes because the stomata are facing the sunlight with no shading causing the temperature to increase as the light intensity does causing water to evaporate into the atmosphere. Temperature is a factor that affects the rate of transpiration in mesophytes because if it becomes too hot on the top of the leaf, this causes them to lose water via transpiration into the atmosphere, thus causing the rate of transpiration to increase. Although these three factors affect the rate of transpiration in hydrophytes, to hydrophytes losing water due to transpiration and osmosis is not important they have more adaptations in order to collect gases (oxygen and carbon dioxide) and store them. (Roberts, 2011)(Jones, 2015)(Class Notes,2015) (Fieldtrip to the Hamilton Gardens)(Everything-ponds.com, 2015)
Adaptations hydrophytes have to maintain water balance:Stomata adaptationsSince hydrophytes they don’t have adaptations to conserve water, they have adaptations to gain sunlight and gases. A structural adaptation that hydrophytes have is that if their leaves float on the surface of the water, their stomata are open all the time. One of the reasons they do this is because the guard cells are always turgid so they are always open and also because hydrophytes have a limited amount of gas under the water so in order to get carbon dioxide for photosynthesis they have to have their stomata open all the time, this causes there to be lots of transpiration occuring but they don’t need to conserve water like xerophytes and mesophytes so it is not a problem for them. Stomata are also on the top of floating leaves to make sure they get enough carbon dioxide gas for photosynthesis to make glucose which is used for respiration and efficient gas exchange, this increases the rate of transpiration because the stomata are now open to more environmental factors that affect the rate of transpiration, but again because they live in places where water is in abundance it is not a problem. If the stomata were on the underside of the leaf it would not affect the water balance as the concentration gradient is even on both sides of the leaf, but would be hard and take a long time for the plant to get sufficient gas (oxygen and carbon dioxide) for photosynthesis and respiration and wouldn’t increase the chance of the plants survival. In hydrophytes that are fully submerged under water, the stomata are barely present and hardly functional, this again is to increase the rate of photosynthesis because it is hard for the plants to get and conserve oxygen and carbon dioxide for photosynthesis and respiration under water and if the stomata stayed open all the time, it would cause some of the gases to escape. (Roberts, 2011)(Jones, 2015)(Class Notes,2015) (Fieldtrip to the Hamilton Gardens)
stem/leaf adaptationsAdaptations that hydrophyte plants have in their leaves and stems that are different to the other plant groups. Hydrophytes have light, hollow stems which are full of Aerenchyma (air spaces in the stems) which help to keep the plants floating. This is a structural adaptation helps the plants to get sufficient gas for photosynthesis and other life processes. If hydrophytes didn’t have light, hollow stems, the plants would find it more difficult to collect gases for processes such as photosynthesis. The stems also aren’t stiff lignified like xerophytes and mesophytes, another structural adaptation. This is because they have no use for the transpiration pull which pulls water up from the roots to the leaves as there is more water outside the plant than in the plant which causes water when needed, to be absorb into the plant via osmosis. They also don’t need to be held upright as the water supports them. If the hydrophytes lived in areas of rough currents, having a lignified stem could cause them to snap and break off resulting in a decreased chance of survival. With submerged hydrophytes like seaweed, they usually don’t have a cuticle or many stomata so that they don’t lose important gases. They have leaves that are thin and like ribbons so to increase the surface area for diffusion. The leaves are structured differently to leaves that float on the surface of the water, submerged leaves are much smaller so not to be damaged in rough water conditions and also don’t contain as many air pockets because they don not need to keep afloat like floating leaves. Also with submerged hydrophytes, they are quite dark in colour because because they are full of chlorophyll to try and get as much light as possible to carry out as much photosynthesis as possible. Some hydrophytes also have leaves that float on the surface. This is because they will have trapped air pockets to help with buoyancy and to keep them on the surface. This is so that the leaves can get light and gases for processes such as photosynthesis which uses carbon dioxide and converts it to glucose and also respiration which uses oxygen and converts it to ATP. The floating leaves also have a waxy cuticle which helps protect the leaf and also limits evaporation of water through the leaf. (Roberts, 2011)(Class Notes,2015) (Fieldtrip to the Hamilton Gardens)(Wikipedia, 2015)
Vascular system adaptationsAdaptations that the vascular system in hydrophytes have. Because carbon dioxide and oxygen are in limited supply in the water where hydrophytes live, they both enter the plant through osmosis but that method is very slow compared to getting it from the atmosphere. This cause the tissues of most hydrophytes to have large air pockets around the cells mostly in the palisade and spongy mesophyll to help create a larger concentration gradient which causes more water and gases to get absorbed through the stem and leaves faster and it also helps to keep them buoyant. Hydrophytes also have very little vascular and support tissues. This is because the water provides the structure and water with absorbed minerals can get to most cells via osmosis. (Powell, 2013)(Roberts, 2011)(Class Notes,2015) (Fieldtrip to the Hamilton Gardens)
Root adaptationsAdaptations that hydrophyte plant roots do or have. Most hydrophytes have very small or absent root systems, some are not even in the ground. This is because the minerals that the plant needs are all water soluble and in the water which allows them to get osmosed into right into the plant and it cells, it also is so that they can move with the tides or currents and not get ripped. The only hydrophytes that do have large roots systems are those that are exposed to strong tides and currents and need anchorage. They also don’t have large root systems because it waste their energy which could be used for other processes, like mitosis. Roots are not needed for water balance.(Powell, 2013)(Roberts, 2011)(Class Notes,2015) (Fieldtrip to the Hamilton Gardens)
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Examples of hydrophytes:
Lemna Minor Plant
https://www.flickr.com/photos/maizahyodo/5787396127 |
Types of Hydrophytes
http://wetlandinfo.ehp.qld.gov.au/wetlands/what-are-wetlands/definitions-classification/classification-systems-background/methods/ |
Water Lilies
http://homes-kid.com/flowers-water-lilies.html |
On reference page are full APA references.
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