Plant physiology is the most important part of botany as it helps to understand how the plant grows up and how it reproduces. The functions of plant organs determine how plant adapts to different habitats, how plant conduct metabolic processes to produce energy, and how this energy transfers. The plant has adaptive strategies that help to adapt quickly to environmental change. Studying of plant hormones might contribute to understanding the way that plant control flower production. It also helps to understand genetic processes, and how these processes adapt to environmental change. Several strategies are developed to protect plants.
The plant has four main organs; roots, stems, leaves and flowers. Plant roots play a vital role in anchoring plants in the substrata, absorbing minerals and water, and produce hormones. Roots have external and internal structures. The external structure of the dicots has a large taproot and numerous small lateral roots or branch roots coming out from it. Adventitious roots help increase the absorption rate and transport capacities of the root system. The internal structure includes the root cap that protects the root apical meristem. It secretes mucilage that acts as a lubricant that is made in the Golgi apparatus. The internal structure also includes root apical meristems – a thin-walled cell that lies behind the root cap. A root hair is another part of the internal structure. It is the primary element of the root hair zone that is beneficial for the plant; as it gives a very high surface area of contact with substrata. Plant stem is the vertical extent of the plant root. It is the axis that connects buds and shoots with leaves. Its function is to transfer the water, minerals, and food from root to the other parts of the plant. It might also work as the food storage area while green stems can produce food. The young stems can conduct photosynthesis as they are green. They also control water loss; as they are coated with the protective coating called cuticle. Stems are herbaceous (non-woody) and woody.
Leaves are the main organs that conduct photosynthesis. It is considered as the food source for the plant. They also play a significant role in gas exchange – Transpiration. The leaf blade lamina has a large surface area that helps the plant to increase the amount of light absorption. A leaf consists of epidermis tissues that cover the upper and lower surface, mesophyll. The chlorophyll existed in the mesophyll cells. It is the primary element of food maker in the plant leaf. Modified leaves play a crucial role in the plant. They can be considered food storage tissues in the bulbs. Plant Flower is the reproduction organ in the plant. It consists of septal, stamen and carpels. Septal are green and very attractive to animals and insects. Stamen contains a filament with the anthers. The carpel has the ovary covering the ovules.
Plants face many threats that may impact their survival. The plant organs have many adaptive strategies to adapt to environmental change. Here are some examples of adaptation of plant organs. The root system developed a variety of adaptation strategies. The Phreatophytes have adapted to the water shortage in the desert environment. They built very long root systems to capture water from the underground close to the water table. It is very clear in the mesquite trees that are considered the longest root systems. Leaves transpiration takes place in the stomates. Stems adaptation is apparent in the rhizomes. Rhizomes are horizontal stems grow substrata and they produce new shoots and roots at the nodes while stolon stems are grown horizontal above the ground, for example, strawberry plants. The plant leaf stomata are located on the lower surface of the leaf to avoid direct sunlight. Foliage leaves – where photosynthesis takes place, are made to repel the animals. It is made to be not delicious or nutritious. They are cheap enough as they spend fewer carbohydrates to be built. Leaves are made to be waterproof, and pathogen resist. They help leaves to survive in different environmental conditions.
Metabolic Process and energy transfer mechanism
There are two metabolic processes; Catabolism –complex molecules break down into simpler molecules and energy release, and anabolism – the combining of the simpler molecules to form complex ones. The two processes require an enzyme as a catalyst. An example of catabolic reaction is breaking down of one glycogen molecule into glucose molecule and energy emits, (endergonic). While combining of two glucose molecules in the presence of energy to form a glycogen molecule is an example of anabolic reaction, (exergonic). The metabolic processes are used in the energy transfer process within the plant. Energy transfers during photosynthesis when CO2 combines with simple sugar to produce complex carbohydrates. This process is carried on the plant chloroplast. The photons of sunlight require energy to generate photosynthesis (endergonic reaction). The plant chlorophyll absorbs sunlight energy and converts it into chemical energy. The photosynthesis process has two reactions, light and dark. In light reactions, the light energy is transferred to electrons in the reaction center chlorophyll. High-energy electrons emit from the reaction center and energy is extracted from these electrons to be used to transport a proton (H+) to the thylakoid interior. This proton is used to conduct photophosphorylation to form ATP (Adenosine triphosphate). In The Dark Reaction, the enzyme Rubisco combines ribulose bisphosphate (RuBP), that contains five Carbon atoms, with CO2 molecules to produce two molecules of simple sugar that contain three carbon atoms that are called G3P (Glyceraldehyde 3-phosphate). G3P is used to generate glucose and regenerate RuBP.
Respiration is another process that the energy transfers from state to another. The complex carbon atoms break down into simpler molecules and generate ATP that is used in another metabolic process. In the respiration process, the carbon atom is oxidized as its oxidization state rise from ground level to +4. NADP+ (Nicotinamide adenine dinucleotide phosphate) removed electrons and converted to NADPH. There are two types of respirations; aerobic respiration that requires oxygen as the electron acceptor, and anaerobic respiration that does not require oxygen (Fermentation). The fermentation process is the conversion of glucose into two molecules of CO2, two molecules of ethanol, and two ATP molecules.
There are some studies shows that plant can survive and adapt to climate change. Some plant can manipulate the flowering time to adapt to environment change, for example, the weedy field mustard. The plant shifts it is flowering few days earlier when it introduced to a dry environment. This is because they take the advantage of the short wet season in dry times. I think this is a vital adaptation strategy as the plant not only shifted the flowering few days earlier, it started to flower a week earlier than that who are introduced to the wetter environment. It is the significate evidence that this plant can adapt to dry conditions. Despite this strategy saved field mustard, it might not help California’s redwood to survive as it might not be able to change fast. I believe that not all plants have the same ability to adapt. Some plants can adapt to hot and wet conditions in tropical rainforest environments. The plants leaves have drip tips that help to drop-off water. The trees have extra support by the buttress and silt roots grow in wet soils. Tropical rainforest plants adapt to minimal sunlight availability as their leaves are large. Some plants grow high-up where there is more sunlight, for example; orchids and ferns. Adaptation in the desert is different as the lack of water and excessive sunlight and high temperature existed. Despite those hard conditions, some plants are adapted to survive in deserts. Succulents can store water in their stems or leaves. This adaptive strategy is not existed in Tropical rainforest plants. Some other plants have no leaves. It is a grand strategy as the lack of leaves help minimize water loss. However, leafless plants can conduct photosynthesis by their green stems. Another useful strategy in the desert is the roots are too long to reach the groundwater. An example of desert plants is cactus.
All of these adaptation strategies show how the plant can survive in very hard conditions. I argue that any plant if it is introduced to any harsh environment, it will definitely adapt to these hard conditions. Just the way of introduction is imperative to ensure the survival of the plant.
Flower is formed from modified leaves when the plant reaches the maturity stage. It stops to produce leaves and starts to produce modified leaves that are known as flowers. Flower formed from the shoot meristem when the meristem stops vegetative growth. A floral meristem divides into the tunica – which produces the outer cell layers, and the corpus – the inner cell layers. The flowering process is divided into two processes; the induction – the first stage of the flowering. In this stage, the vegetative meristem form and function will change and the flower will develop. The second stage is called the vocation – floral meristem is developed. There are four whorls; septal, petals, stamen and carpels. Three genes control the whorls processes. Their names are; A, B and C. Each whorl is formed by the effect of one of two genes. For example, A alone is for sepals, A&B is for petals, B&C is for stamens and C alone is for Carpels (Lack and Evans, 2001). In my opinion, this assumption cannot be granted as a theory. I cannot find any proof that those genes are responsible for those whorls. I think this is an only prediction.
Mauseth, J. (1998). Botany. Boston: Jones and Bartlett Publishers.
Flowers are the reproduction organ in the plant. The reproduction process is doing by a mechanism called pollen dispersal. Many dispersal strategies are related to the environment and habitat. Plant seeds can be dispersed by the wind, animal, water and ballistic.
- Wind dispersal: Seeds that are dispersal by the wind should be lighter and smaller in size than other seeds. It helps seed to travel quickly by the wind. Seed structure has a like-wings or fluff structures. These structures help seed to hang in the air for a long time and to travel long distances. Despite this is the most common strategy, I can find some difficulties in this approach. For instance; most seeds cannot reach their suitable place and they might die. They also have fewer nutrients to live as their endosperm is small.
- Animal dispersal: Seed can be considered as food for animals or in the fruit itself. Animals can feed on these seeds and then the animal might travel it to another location and come out when animal spits or blows them. I believe this strategy is less effective because it depends on the animal The seeds would never be transferred unless the animal takes them.
- Water dispersal: Plants use water to disperse seeds. Coconuts have a waterproof wooden casing that allows them to travel long distances in water. I guess this is also not a common way to disperse seeds. It is too risky and also depends on the transport environment.
- Ballistic dispersal: Seeds use the explosion to disperse. Such as seeds that are located in pods, as when the pod dries, it explodes and expelling seeds, hazel as a good example of this strategy.
From the previous approaches, it would be maintained that the wind strategy is more efficient and less risky than other. It does not require a host to be traveled.
The plant needs hormones for the development of flowers and fruits, and for inhibiting growth. A hormone is an organic compound help regulates plant activities. There are some well-known hormones of the plant. They are; Auxins, Gibberellins, Kinetin, Cytokines, and ethylene. Auxin is a well-known plant hormone that occurs in seeds, stem tips, fruit, leaves, and buds. Their production and distribution are affected by some physical properties of surroundings, such as light, gravity, and some chemical substances. It existed on the dark side of the plant as the light is present on only one side. Auxin helps cells to elongate and curve the stem towards the light source. Gibberellin is responsible for stem growth as it is more efficient in the stems. It also affects the cell division rate, flowering, and the plant growth induction at low temperatures. Kinetin acts as Auxin; as it is responsible for plant growth and development. If the plant does not have kinetin in the tissue, neither roots nor buds are developed. The cytokine is the hormone that responsible for cell division and affect the cell differentiation in plant leaves. Ethylene is the hormone that affects rotting in the plant. It is the only gaseous hormone in the plant. It can diffuse through plant tissue to air.
As we have seen, plant hormones play vital roles in plant activities and development. Any absence or damage in one of any hormones, it might affect the whole plant.
Many genetic processes take place in the plant. The genetic processes are; mitosis, meiosis and inheritance processes. Mitosis is the process of division of plant cells to produce two copies in the same cell called daughter cells. Each one has the same genetic material of the parent cell. This process has six phases. Interphase – chromosome is duplicating in the cell as a preparation for mitosis. The second phase is prophase in which chromosomes are formed from condensed chromatin. The chromosomes’ pairs are joined the centromere. During metaphase, the third stage, the chromosomes move to the different cell ends. During anaphase, chromosome pairs separate. Half moves to one end of the cell and the second half moves to the other end, and the microtubules elongate the cell. In telophase, the chromosome turns on chromatin once again. Meiosis is another genetic process in the plant. It is the same of mitosis processes as it has five phases; Interphase, prophase, metaphase, anaphase, and telophase. The difference is that the cell division in meiosis reduces the number of chromosomes in the parent cell and produces four gamete cells.
Inheritance, the most important genetic process, I believe, is discussed by Gregor Mendel, 1866 (Biotechlearn.org.nz, 2015). He worked on pea plants. I think this is the key point in plant genetic processes. The botanists thought that if plants are cross-bred with a plant like itself, the offsprings would be the same. For example, if yellow seeds and green seeds are bred, the offspring would be yellow. Mendel has argued that some traits’ genetic make-ups are hidden or recessive, others are dominant. I would like here to explain the Mendel experiment of pea plants. When one yellow-seed (YY) is purebred with a green-seed (yy), the offsprings would be four heterozygous yellow-seeds. However, the breeding of two of the heterozygous traits would produce three yellow-seeds (Yy) and one green-seed (yy). This will prove that the green gene is present but masked or recessive.
Alexander, T., Burnett, R. and Zim, H. (1970). Botany. New York: Golden Press.
The adaptation to environments and habitats
Some plants that are growing up in very harsh conditions experience natural genetic modification. It means that their genetic processes are changed to be easily adapted to the hard conditions. Some plants have a range of epigenomic diversity that helps plant to adapt to various environments. The plants that are collected from a different location from all over the world found their epigenomes are different. This can explain how plants are adapted to different environments without any change in plant DNA. Epigenomic modification changes the gene expression without any change in the DNA alphabet (A-T-C-G). Another adaptation strategy can be found in Arabidopsis thaliana. A study held by Dr. Salt gathered around 300 Arabidopsis thaliana seeds from all over the world (ScienceDaily, 2015). This plant can bear with high levels of sodium. This plant has been grown in a non-saline soil. By comparing the genome of this plant with those who grown up near to the coastal line, Dr. Salt found that the plant that accumulates the highest level of sodium had a reduced level of gene HTK 1. This gene is responsible for regulating sodium distribution in leaves. I believe that this is one of the first evidence that is connecting genetic change with the adaptation of the plants. Another two plants; Ribwort plantain and Sheep fescue, show the ability to respond to climate change. There is a genetic differentiation with a long-term climate treatment. The genetic difference is shown between climate treated plants and untreated plants.
Threats to Plant survival
Plants are facing many threats that might affect their survival. Threats have been addressed, and strategies have been taken to preserve plants. Some of these treats are; climate change, illegal trade, and human activities. Climate change can be considered the most threat that affects plants. Temperature effect can control the plant distributions, for example, Palmae/ Arecaceae cannot deal with cold temperatures as their meristem is susceptible to frost. Climate change is said to turn forests to be carbon emitters. It also affects the rate of growth of the plant. The Climate Change Act in the UK is the one of the most effective acts that deal with the climate change issue. It sets 2050 target that aims to reduce Greenhouse Gas (GHG) emissions by 2050. The success of this act is it the UK has achieved the 1st carbon budged with emission 36 MtCO2e below the cap of 3.018 MtCO2e (Gov.uk, 2015). Another threat that might impact endangered plant species is the Illegal trade of endangered plant species. One of the widely known illegal wildlife trade is South East Asia. Orchids are the most species that illegally trade. There are more than 400 species of ornamental plants in illicit trade (Mathewson, 2015). The Convention on International Trade in Endangered Species (CITES) is an international agreement to prevent illegal trade of the endangered wild animal and plants. It is an exquisite convention as it succeeded to limit the illegal trade worldwide. Switzerland succeeded in implementing CITES as the threat of extinction of the species has been mitigated, for instance, Vicugans or certain medicinal plants. CITES protects about 30,000 plant species against over-exploitation through illegal trade (cites.org, 2015). Finally, human activities, for example, deforestation, urban expansion, and industrial activities might threat plant populations. IUCN, the International Union for Convention of Nature, has established protected area that considered the most effective strategy to protect wildlife. IUCN defines protected area as a clearly defined geographical space recognized, dedicated and managed, through legal or other effective means, to achieve the long-term conservation of nature with associated ecosystem service and culture value, (Iucn.org, 2015). I argue that the effectiveness of this strategy is it is divided into six categories that cover all sides of wildlife protection.
Conservative strategies are developed to help plant to survive and to mitigate the threat effects. Several successful strategies are implemented and others in the progress to be fully implemented.
- Alexander, T., Burnett, R. and Zim, H. (1970). Botany. New York: Golden Press.
- Berger, S., Sinha, A. and Roitsch, T. (2007). Plant physiology meets phytopathology: plant primary metabolism and plant pathogen interactions. Journal of Experimental Botany, 58(15-16), pp.4019-4026.
- org.nz, (2015). Mendel’s principles of inheritance | Biotech Learning Hub. [online] Available at: http://biotechlearn.org.nz/themes/mendel_and_inheritance/mendel_s_principles_of_inheritance [Accessed 6 Dec. 2015].
- Cartolano, M., Castillo, R., Efremova, N., Kuckenberg, M., Zethof, J., Gerats, T., Schwarz-Sommer, Z. and Vandenbussche, M. (2007). A conserved microRNA module exerts homeotic control over Petunia hybrida and Antirrhinum majus floral organ identity. Nature Genetics, 39(7), pp.901-905.
- org, (2015). The CITES species | CITES. [online] Available at: https://www.cites.org/eng/disc/species.php [Accessed 12 Dec. 2015].
- org, (2015). What is CITES? | CITES. [online] Available at: https://www.cites.org/eng/disc/what.php [Accessed 12 Dec. 2015].
- com, (2015). Types of Plant Hormones. [online] Available at: http://www.cliffsnotes.com/study-guides/biology/plant-biology/growth-of-plants/types-of-plant-hormones [Accessed 29 Nov. 2015].
- com, (2015). Desert Plant Survival Page 2 – DesertUSA. [online] Available at: http://www.desertusa.com/du_plantsurv2.html [Accessed 22 Nov. 2015].
- com, (2015). Flower Anatomy Printout – EnchantedLearning.com. [online] Available at: http://www.enchantedlearning.com/subjects/plants/printouts/floweranatomy.shtml [Accessed 29 Nov. 2015].
- uk, (2015). [pdf] Available at: https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/414241/20150319_Progress_to_emissions_reductions_targets_final.pdf [Accessed 12 Dec. 2015].
- org, (2015). IUCN – Global Protected Areas Programme. [online] Available at: https://www.iucn.org/about/work/programmes/gpap_home/pas_gpap/ [Accessed 12 Dec. 2015].
- Lack, A. and Evans, D. (2001). Plant biology. Oxford: BIOS Scientific Publishers.
- Levetin, E. and McMahon, K. (2011). Plants & society. New York: McGraw-Hill.
- blogspot.co.uk, (2015). Plant Life: Mitosis and Meiosis. [online] Available at: http://lifeofplant.blogspot.co.uk/2011/03/mitosis-and-meiosis.html?_sm_au_=iVVCH7PD6R863Dj2 [Accessed 5 Dec. 2015].
- Woodwell, G. (2015). plant | biology :: Reproduction and life histories. [online] Encyclopedia Britannica. Available at: http://www.britannica.com/topic/plant/Reproduction-and-life-histories#toc66103 [Accessed 23 Nov. 2015].
- Mathewson, S. (2015). Illegal Wildlife Trade: Sale of Restricted Wild Orchids Goes Unchallenged in Southeast Asia, Say Researchers. [online] Nature World News. Available at: http://www.natureworldnews.com/articles/16761/20150917/illegal-wildlife-trade-wild-orchids-go-unnoticed-southeast-asia.htm [Accessed 11 Dec. 2015].
- Mauseth, J. (1998). Botany. Boston: Jones and Bartlett Publishers.
- Mora, C., Caldwell, I., Caldwell, J., Fisher, M., Genco, B. and Running, S. (2015). Suitable Days for Plant Growth Disappear under Projected Climate Change: Potential Human and Biotic Vulnerability. PLOS Biology, 13(6), p.e1002167.
- Nathan, R., Bullock, J., Ronce, O. and Schurr, F. (2001). Seed Dispersal. Encyclopedia of Life Sciences.
- Nelson, R. (2015). Plant Growth Hormones – Untamed Science. [online] Untamed Science. Available at: http://www.untamedscience.com/biology/plants/plant-growth-hormones/ [Accessed 29 Nov. 2015].
- Salk Institute for Biological Studies, (2013). Hidden layer of genome unveils how plants may adapt to environments throughout the world – Salk Institute for Biological Studies. [online] Available at: http://www.salk.edu/news-release/hidden-layer-of-genome-unveils-how-plants-may-adapt-to-environments-throughout-the-world/ [Accessed 12 Dec. 2015].
- Schooley, J. (1997). Introduction to botany. Albany: Delmar Publishers.
- ScienceDaily, (2015). Plants can adapt genetically to survive harsh environments. [online] Available at: http://www.sciencedaily.com/releases/2011/01/110131161344.htm [Accessed 12 Dec. 2015].
- ScienceDaily, (2015). Plants cope with climate change at genetic level: Researchers find experimental climate challenges lead to rapid genetic changes. [online] Available at: http://www.sciencedaily.com/releases/2015/12/151210031830.htm [Accessed 12 Dec. 2015].
- com, (2015). Animation. [online] Available at: http://www.sumanasinc.com/webcontent/animations/content/meiosis.html [Accessed 4 Dec. 2015].
- org.uk, (2015). The Climate Change Act and UK regulations | Committee on Climate Change. [online] Available at: https://www.theccc.org.uk/tackling-climate-change/the-legal-landscape/global-action-on-climate-change/ [Accessed 12 Dec. 2015].
- wiseGEEK, (2015). What is Plant Mitosis? (with picture). [online] Available at: http://www.wisegeek.com/what-is-plant-mitosis.htm [Accessed 5 Dec. 2015].
- YouTube, (2015). Plant Organs: Structure and Function. [online] Available at: https://www.youtube.com/watch?v=AnxDZNdq_0U [Accessed 22 Nov. 2015].