Senescence is the age-dependent deterioration process at the cellular, tissue, organ, or organismal level, leading to death or the end of the life span (Nooden, 1988). Leaf senescence is an organ level senescence but is often intimately associated with cellular or organismal death (Lim et al., 2007). According to Betania et al. (2000), it is the last stage of leaf development. The senescence process is started by the breakdown of chloroplast (Gepstein, 2004). Next, it is followed by macromolecules catabolism for example nucleic acids, proteins, and lipids (Ulker et al., 1997). Final stage for leaf senescence is the degradation of mitochondria and nuclei (Gan and Amasino, 1997; Lim et al., 2007). Nutrients released by leaf senescence for example nitrogen, phosphorus, and minerals will be invested to younger leaves and growing seeds, or are stored for the next growing season and it can be viewed that as a recycling program at the organismal level (Betania et al., 2000). …show more content…
On the other hand, senescence process including senescence rate and molecular nature is influenced by various environmental and internal factors (Lim et al., 2007). The internal factors influencing leaf senescence includes phytohormones such as cytokinins, ethylene, auxin, JA, ABA, and SA, while the external factors includes UV rays , nutrient limitation, temperature, drought, shading, and pathogen attach or wounding. It can be said that to form a complex network of regulatory pathways for senescence, there should be an existence of various pathways responding to several external and internal factors all the pathways should be interconnected (He et al., 2001). Having said that, leaf senescence should be an excellently regulated process, taking into account its potential role in plants health and the various factors involved in senescence control (Lim et al.,
Plant hormones are certain chemicals present in plants that control plant growth and development by affecting the division, differentiation, and elongation of cells. (Campbell, 2008) Each hormone has multiple effects depending on its site of action, its concentrations, and the developing stage of the plant. (Campbell, 2008) Auxin is a plant hormone that is synthesized within the apical meristems and young leaves of a growing plant. Auxin stimulates stem elongation when it is present is low concentrations. It promotes the formations of lateral and adventitious roots, regulates development of fruit, enhances apical dominance, functions in gravitropism and phototropism, promotes vascular differentiation, and retards leaf abscission. Gibberellic acid is one of several plant hormones that govern a plant’s growth. Gibberellins allow for stem elongation in plants. Plants without enough of this hormone tend to grow short or stunted. This chemical is high in the element potassium, which is one the main components of plant fertilizer and very important for plant growth on its own. The...
The theme of the book as it relates to the American Dream is those who take advantage by becoming covetous and acquisitive. The Clutters in this book are described as the ideal American Dream family. Herb Clutter is the head man of the house who makes sure that his family and financial situations are in order. Herb started off with a struggle but eventually worked hard to become the man he became. Even though they were viewed as a rich family toward the community they did have underlying issues that weren’t visible to the outside world. Dick and Perry on the other hand are those who were unable to achieve the American Dream so they were willing to do anything to become successful the easy way even if that means stealing from others. They
It is a large topic of discussion whether legality or morality is more important. Barbara Kingsolver poses this debate in her book The Bean Trees. This book takes place in the 1980s in Putnam County, Kentucky, and begins with Taylor, the main character, leaving her old house behind to start fresh. Taylor does not get the fresh start she is looking for and instead is given an unwanted responsibility of raising a child. Along her journey to find home, Taylor meets many new friends who help her. Through the illegal ways that Turtle Esperanza and Estevan are taken in by Taylor and Mattie, Kingsolver proves that with regard to family, morality is more important than legality.
Freudian Analysis of Marigolds Most of the time there is a moment in life where one realizes they have lost all innocence and gained some compassion. “Marigolds” shows how one young girl transferred from a child to a young adult through her life experiences. Throughout this story, another young, but at the same time old in her prime, lady’s experiences are revealed: the author’s. In this short story, “Marigolds,” Eugenia Collier’s subconscious is unmasked through symbolism, diction, and Elizabeth’s actions.
Abandonment is a feeling known to many people. There are different types and levels of abandonment. In The Bean Trees by Barbara Kingsolver, many characters have been introduced to the feeling of abandonment. Abandoning or being abandoned is constant in the novel and Kingsolver uses it to link all of the characters together.
N.p., 29 Mar. 2014. Web. 28 Mar. 2014. "Related Topics. " Plant Science Research : Ozone Effects on Plants.
Each plant species has a unique pattern of resource allocation that is genetically determined but not fixed. Plants can adjust there allocation pattern when they experience different environments and the presence of other species. Phenotypic plasticity goes hand in hand with resource allocation as well. When a plant has to adjust itʻs resource allocation, sometimes it uses itʻs resources to help the plant grow different characteristic so that the plant can have a greater chance of living in the environment. For example, if a plant from an environment that does not experience wind on the regular basis enters a new environment that has a lot of wind the plant may change itʻs resource allocation and spend more of itʻs resources growing deeper
“Al Condraj sat on the bench he had made and smelled the parsley garden and didn’t feel humiliated anymore. But nothing could stop him from hating the two men, even though he knew they hadn’t done anything they shouldn’t have done.” (The Parsley Garden, Junior Great Books, Series 6, pg.42)
In the novel Purple Hibiscus written by C. Adichie the concept of cruelty is incorporated in the text to express one's vigor when it come to their beliefs and shows the extent of one's insecurities. This idea is expressed by the character Eugene and in his personality. Him and the concept of cruelty is then show in many aspects in Kambili's life and is the major obstacle for Kambili. It also reveals Eugene's insecurities and his strong belief in his religion.
Humans undergo several stages during their lifetime including growth, development, reproduction and senescence. Senescence is defined as the deteriorative biological changes that organisms experience as they age eventually leading to death. These changes include low metabolism, a weak immune system, memory loss, poor vision and loss of hearing. Senescence begins in humans during their post-reproductive years. However, gerontology research has shown that individuals who reproduce late have longer life spans compared to individuals who reproduce early. Nonetheless, it does not indicate that senescence is inevitable. All organisms experience senescence, but at different rates and time. Many genetic diseases such as Alzheimer’s disease and Huntington’s disease are prevalent in older individuals and the symptoms being to appear in middle adulthood. The causes of genetic diseases and disabilities in older individuals are explained by three evolutionary theories: antagonistic pleiotropy theory, mutation accumulation theory and disposable soma theory. These theories suggest that favorable natural selection and heavy allocation of resources for somatic maintenance during the reproductive period decreases the chances of genetic diseases in younger individuals.
Yang, Q. (2009). Cellular senescence, telomere recombination and maintenance. Cytogenetic and Genome Research, 122(3-4), 211-8. Retrieved from http://search.proquest.com/docview/224206989?accountid=28496
All dramatic productions feature the elements of drama. Following a viewing of the scene ‘Someone’s crying’ from the 1993 movie ‘The Secret Garden’ three of the elements of drama have been assessed. Role, character and relationships have been utilised in ‘The Secret Garden’ to create anxiety and suspense, enticing the viewer to solve the mysteries the Secret Garden presents. The protagonist in the scene is a young girl, around the age of ten who during the night leaves her room to explore her residence. The protagonist narrates the scene; she begins by stating that the ‘house seems dead like under a spell’. This makes the viewer anxious and fearful for the safety of our young protagonist. The protagonist is brave. She pushes open a door and
How Light Affects the Stomatal Opening in a Leaf Abstract = == == ==
As the years pass and we began to age we all notice a change and this change that comes is not the apparent physical change but rather the attitudes and personification people have as we enter our old age. It seems as though, as we begin to age we notice that a sense of respect begins to build from the younger generation. According to the book “social perspectives on aging, “ it states that ‘today most social gerontologists prefer activity theory, which assumes that older people benefit both themselves and their society if they remain active and try to continue to perform the roles they had before they aged.” In other words the elderly are benefiting from what they built on their own over their lifetime and they are also benefiting from society
Plant defences are those mechanisms employed by plants in response to herbivory and parasitism. According to Hanley et al. (2007), “the tissues of virtually all terrestrial, freshwater, and marine plants have qualities that to some degree reduce herbivory, including low nitrogen concentration, low moisture content, toxins or digestibility-reducing compounds”. The type of chemical defence may be species specific (Scott 2008). The defences that plants possess may be in the form of chemical production or in the form of physical defences such as thorns or spikes and even through reinforced, rigid leaves. “The compounds that are produced in response to herbivory can either have a direct effect on the attacker itself (e.g. toxins or digestibility reducers), or serve as indirect defenses by attracting the natural enemies of the herbivores” (Bezemer & van Dam 2005). This essay will focus on chemical plant defences and in particular the effects of terpenes, phenolics, nitrogen-based defences as well as allelopathy in plants.