Ecological niche
Xerophytes are found in very dry and often hot environments this means that these plants have had to adapt to survive in these harsh conditions where there is often a shortage of water. The xerophyte plants have had to adapt in order to carry out essential cellular processes that allow the plant to gain enough energy in order to survive and grow. Photosynthesis is a process in which all plants must carry out in order to survive. In order for photosynthesis to occur water and carbon dioxide are two raw materials that are need. Because xerophyte plants live in environments where there is often a shortage of water they have had to adapt in order to obtain a successful level of water within the plant in order for this process to occur. Photosynthesis produces glucoses which the plant can then store as starch or use in the processes of respiration where oxygen and glucose are converted into ATP (energy) which is then used by the plant to grow and survive. Xerophyte plants have adapted in order to obtain the correct amount of water to carry out the important processes that allow the plant to survive and grow successful in its environment.
https://www.youtube.com/watch?v=xIVixvcR4Jc
http://tinyurl.com/codhbwh
https://prezi.com/khpnr-llvg42/mesophytes-xerophytes-and-hydrophytes/
Adaptations
Xerophyte plants live in extremely dry and hot environments meaning they have had to adapt in order to survive and control the water levels within the plant, they do this by preventing water loss. Xerophyte leaves are either extremely small or not there all together; many leaves have been reduced to spines. The plants have adapted in this way as if they were to have large leaves there would be a larger surface area for evaporation of water to occur, and because these plants live in dry environments water must be conserved in order for the plant to survive. If the plant does have small leaves they will have a very thick waxy cuticle to prevent the evaporation of water, as living in a hot environment means water will evaporate at a faster rate. The leaves and stem of the xerophyte plants may also be a silver colour meaning they contain less chloroplast which can be a slight disadvantage as the rate of photosynthesis will be reduced due to there being less chloroplast but the silver colour will reflect the sunlight causing less water to evaporate meaning water loss will be less. The plant will also be able to control its temperature better. Leaves of a xerophyte plants can also roll up causing the stomata to be inside the roll where moisture will become trapped and the environment around the stomata to be more humid slowing the rate of transpiration as the concentration gradient of water between the inside of the plant and outside of the plant will be less, therefore the water loss will be less as water moves from a high concentration to a low concentration. Some leaves will also be shaped so that when it does rain water will travel down the leaf and into the plant. The adaptation of leaves is physical adaptation as it involves the plant changing a physical feature in order for it to maintain water balance Xerophyte plants have to conserve water as rain is scarce in their environment meaning if the plant lost to much water it would no longer be able to carry out photosynthesis as water is a raw material needed for this cellular process to occur. If photosynthesis did not occur then little/no glucose would be made so no ATP would be produced due to little respiration. Xerophyte plants also need water to keep there cells turgid in order for the plant to uphold its upright structure. The plants need to stay upright in order for their leaves to absorb enough sunlight energy for them to carry out photosynthesis.
The stomata are found on the bottom of the leaf, as this is where the temperature is the coolest, or if the plant does not have leaves then they will be located on the stem. Xerophyte plants have fewer stomata to reduce water loss via transpiration. Stomata can be found in sunken pits, this will increase the air humidity around the stomata meaning water loss will be less and more water will be conserved within the plant. The stomata may also be surrounded by tiny hairs on the leaf or stem, these hairs are called trichomes and slow down the rate transpiration as it shelters the stomata from harsh winds. If the wind blew straight overt the stomata then water would be lost form the surface of the plant meaning more water, which the plant needs in order to survive, would be lost via transpiration. Stomata may also be located inside leafs that have rolled up, in this position less water will be lost as the humidity around the stomata will be higher causing the concentration gradient between the inside of the plant and out side of the plant to be less so less water will be lost. Many xerophyte plants are C4 plants which means they can carry out photosynthesis is two different stages. C4 plants are able to close their stomata during the day when it is hot and humid to prevent water loss via transpiration, they then open their stomata at night when is cooler and the diffusion of gases in and out of the cell will occur then and less water will be lost. The C4 process starts of with carbon dioxide entering the plant through diffusion form the high concentration of outside the plant to the low concentration of the inside of the plant, this process occurs at night. The carbon dioxide then enters the spongy mesophyll layer of the leaf where it is converted into a 4-carbon compound called oxaloacetic acid, which is then converted into malice acid, which is then stored with in the leaf for later use. The second stage of the C4 process occurs at daytime where the stomata close up to prevent water loss and sunlight energy is absorbed and used to carry out photosynthesis where water and carbon dioxide (which was diffused into the plant the night before) are converted into glucose which is the used in respiration to form ATP. This adaptation is a physiological of the xerophyte as it involves the plant carrying out a special function in order to survive.The C4 process conserves water as it prevents water loss by closing the stomata in the hottest parts of the day in order to stop transpiration where water is evaporated out of the plant. The stomata have adapted in several ways to keep water balance within the plant because water is lost so easily in the xerophytes environments they must adapt in order to keep the right water leaves in the plant in order for it to survive and carry out essential life process such photosynthesis and cell division.
The roots of xerophyte plants are well developed and reach out for long distances but only grow close to the soil surface the roots grow this way because when it does rain water does not travel deep into the ground before its evaporated due to the intense heat, so this allows them to absorb the plenty of water before it evaporates. This adaptation helps the plant to keep water balance but it does put the plant in danger of being blown away in high wind conditions as the roots do not anchor the plant as well. The roots also have large capacity which allows them to hold large amounts of water, as when it does rain the plant will want to absorb as much water as possible in order to keep water balance within the plant as water is needed to keep the calls turgid and to carry out photosynthesis and get minerals into the plant. The roots also have tiny root hairs that increases the surface area of the roots which allows them to absorb more water. The stems of xerophyte plants are also succulent and able to store large amounts of water in order to keep water balance within the plant, the movement of water from the roots to the stem of the plant is also an important processes that helps cool the plant and reduce water from evaporating. Water is able to move through the plant as the xylem tissues are well developed and are able to hold large amounts of water. The well developed xylem helps keep water balance within the plant as water needs to be transported from the roots to the stem where it can be used in cellular process such as photosynthesis and cell division. The stem of the plant also has supporting tissues (fibers) which allows the plant to stay upright for longer even when water levels are low and the cells begin to become flaccid, this means that the plant will still be able to absorb sunlight in order to carry out photosynthesis.
http://www.conservancy.co.uk/learn/downloads/fieldtrips/xerophytes.pdf
http://www.thestudentroom.co.uk/wiki/Revision:Xerophytes_and_Hydrophytes
http://www.bbc.co.uk/bitesize/higher/biology/genetics_adaptation/maintaining_water_balance/revision/4/
http://loretocollegebiology.weebly.com/mesophytes-xerophytes-and-hydrophytes.html
Life processes ecology and evolution
Rachel Heeney and Professor Peter Shepherd
Pearson
Published in 2012
2 June
Field trip voice recording
http://ejdio.weebly.com
http://www.thestudentroom.co.uk/wiki/Revision:Xerophytes_and_Hydrophytes
http://www.bbc.co.uk/bitesize/higher/biology/genetics_adaptation/maintaining_water_balance/revision/4/
http://loretocollegebiology.weebly.com/mesophytes-xerophytes-and-hydrophytes.html
Life processes ecology and evolution
Rachel Heeney and Professor Peter Shepherd
Pearson
Published in 2012
2 June
Field trip voice recording
http://ejdio.weebly.com