The Role of Ethylene In Fruit Ripening and Its Interaction with the Development of Fruit Color - Literature review Example

Institution : xxxxxxxxxxx Title : Literature Review Tutor : xxxxxxxxxxx Course : xxxxxxxxxxx @2012 Introduction Ethylene (C2H4) is a hormone in plants that controls a wide range of environmental responses and developmental processes. One of the most significant is the role of the hormone in the ripening of fruits. In addition ethylene also works towards the development of fruit colour. Ethylene is a product of biosynthesis of two major regulatory enzymes; ACC oxidase and ACC synthase (Oetiker & Yang, 2006, p398). In many fruits ethylene is usually generated in small quantities. However the hormone plays a very critical role in contributing to the ripening of fruits and also the development of colour in fruits. Various studies have therefore been conducted in order to analyze the contribution of ethylene in plants specifically fruits. This particular paper seeks to provide a review of literature concerning role of ethylene in fruit ripening and its interaction with the development of fruit colour. Barry and Giovannoni (2007, p143) highlights that the process of fruits ripening characterizes a unique coordination of biochemical and developmental pathways that result to changes in colour, aroma ,texture and the nutritional qualities that exist in a mature plant that is capable of bearing seeds. Barry and Giovannoni (2007, p143) further highlight that ethylene a plant hormone with gaseous attributes plays a significant role in the ripening of a wide range of fruits essentially those that nutritional values to human diets. According to Barry and Giovannoni (2007, p144) the absence of ethane within the ripening process may result to failure of the ripening process to the level of completion. However once ethylene exists ripening becomes a one way process and profitable aspects of ethylene in influencing the production of high quality fruits is attained. Ethylene also influences over ripening and decay in high extremes. This is evidently true after harvesting has taken place. Barry and Giovannoni (2007, p143) highlights that in most cases in order to control over ripening and even the decay fruits efforts have been directed towards controlling the level of ethylene hormone in fruits. Based on this fact it can be argued that ethylene is a crucial aspect in the ripening of fruits and the colour of the fruit (Barry and Giovannoni, 2007, p143). The role of ethylene in influencing the ripening of fruits has been investigated widely and several findings have been arrived at However Khan (2006, p152) highlights that non-conclusive evidence has been arrived at the exact role that ethylene plays in the ripening of fruits. Most of the studies have focused in examining the role of ethylene is various climacteric fruits. Ramina et al (2007, p168) points out that the production of ethylene is a significant stage in the initiation of the ripening process in fruit. This is based on the fact that the signal of ethylene produced during this particular period ignites various changes that result to the conversion of starch into free sugars , changes in the degradation of chlorophyll, leading to a change in the colour of the fruit , changes in the aroma and peel softening. Vidhuet al (2005) undertook a study to examine the role of ethylene in the ripening of climacteric fruits. Climacteric fruits are fruits that have the attribute of a high rate respiration essentially during the ripening process. The high respiration rate therefore results to the ability of the fruit to ripen even after being harvested from the tree (Kader, 2002). The method of the study that was used by Vidhu et al (2005) in order to examine fruit ripening in climacteric fruits involved the use of an exotic variety of mangos known as ‘Dashehari’ (Mangiferaindica cv. Dashehari). The mango is usually cultivated in the Northern parts of India. Vidhu et al (2005) reveal that one of the distinguishing attributes of the Dashehari’ mango is that it suffers from uneven and rapid ripening which makes it to unfit for the purpose of export. Various physiological and biochemical studies have been undertaken in order to examine and understand the ripening process in this particular mango species. However, Vidhu et al (2005) highlight that no substantial evidence was gather to determine the existing molecular compositions that influence softening and even the ripening of the mango. The study by Vidhu et al (2005) therefore involved an experimental method of characterization and isolation of an α-expansin gene;MiExpA1, the gene is usually linked to softening in mango. The gene was then subjected to dual control, through being exposed to a 90 minutes ethylene treatment, which was proceeded by the ripening of the peak after three days of exposing the gene to ethylene treatment. The findings of the study reveled that at the protein point, there was an indication of expansin which was detected on the second day of the experiment. This proceeded through out the process of softening. The experiment further revealed that MiExpA1 expression is basically ethylene dependent; in addition its appearance is increased with an increase in the level of the mango ripening. From the experimentation of Dashehari’ mango Vidhu et al (2005) concluded that the ripening climacteric fruits is majorly triggered or influenced by the ethylene, which further leads to the activation of various cell walls hydrolases. The activation of the walls further results to disassemble of the walls which further results softening. In addition after ripening is initiated the interaction of the existence of ethylene leads to the development of colour in fruits (Adams et al, 2004, p332). Adams et al (2004,p331) highlight that the beginning of ripening is in most cases characterized by changes of the colour of the fruit .This event of ripening gives an Indication of the presence of an underlying genetic mechanism that influences the process of ripening and further the interaction of the development of the fruit colour. Mayuoni,(2011,p50) undertook a study to examine how ethylene influences the internal qualities that exist in citrus fruits such as ripening , aroma and colour .One of the qualities examined was also the aspect of colour . Mayuoni, (2011,p51 ) highlight that citrus fruit is one of the non –climacteric fruits, nevertheless when the citrus fruit is exposed to exogenous ethylene ,for instance the degreening of ethylene , various processes that are ripening related do occur in the peel tissues. One of the processes is the destruction of pigments of green chlorophyll and the buildup yellow/orange carotenoids. The study by Mayuoni, (2011, p53) examined the probable effects ethylene on various species of citrus fruits oranges, Satsuma’ mandarins and grapefruit. The findings of the study revealed that exposure of citric fruits to ethylene boosted the peel colour break. In addition ethylene degreening had an effect on acid contents and the amount of juice. The study concluded that in despite of the fact that ethylene had an impact on the peel colour break, there is a great possibility that ethylene is not necessary greatly involved in the process of ripening in citrus fruits as a result it does not damage the internal qualities of the fruit. The transition of a fruit from the ripe state to the unripe state can also be used to highlight the role of ethylene in the ripening of a fruit and the change of colour. Prinsi et al (2011, p 51) highlights that various physiological and biochemical events describe the transition of a certain fruit from the ripe state to the unripe state. As a result, the function of ethylene in the transformation of the fruit can carefully be examined. Prinsi et al (2011, p 52) conducted a proteomic analysis on the mesocarp of the peach fruit. The study was aimed at evaluating the physiological and biochemical events that take place in the fruit during the transition from the ripe to the unripe state. The study also investigated the role of ethylene and the changes that were brought about by the hormone during the transition phase. The method of study involved undertaking a comparative analysis of two peach fruits. The two fruits were then subjected different levels of external ethylene as the changes that occurred from the stages of ripe to unripe were measured and recorded( Prinsi et al , 2011, p 55) . The findings of the study revealed that the exposure to external ethylene influenced physiological and biochemical changes that occurred in the two fruits under study. One of findings arrived at is that the fruits maintained their tissue integrity as they moved from the ripe to the unripe state. In addition a change in the colour of the fruits was detected as indicated by figure I below; (Prinsi et al, 2011, p 60). Figure 1 Pech et al (2008, p115) highlights that ethylene contributes to the ripening of fruits with various distinctive behaviours. According to Pech et al (2008,p115) most studies that have been undertaken on the role of ethylene in the fruit ripening process have in most cases focused on examining ripening in climacteric fruits as opposed to non-climacteric fruits. According to Burg (2004, p29) climacteric behaviour is a significant determinant of the rate of ripening and storability. Pech et al (2008) however undertook a study to examine the role of ethylene in the ripening of fruits with both climacteric and non –climacteric behavior. The study method used a cantaloupe melon which in most cases exhibits the characteristics of non-climacteric and climacteric genotypes. Pech et al (2008) developed a segregation population that was from a cross between a non –climatic melon Songwhan Charmin(c. melovar chinensis ) and a climatic melon Charebtias melon (C.melovarcantalupensis cv Vedrantais ). The experiment basically involved the inhibition of the production of ethylene through biotechnology. Pech et al (2008,p116) further highlights that the initiative or method of crossing the climatic melon Charebtias melon and the non climatic melon signified that climacteric character is in most cases generically conferred and dominated by only two duplicated loci. By examining the segregation of the development of abscission layer (AI) of the ethylene and peduncle production, the study was able to reveal that the climacteric character was mainly controlled by (Al-3 and Al -4)which are the two independent loci. The findings of the study indicated that that ethylene dependent (climacteric) and ethylene independent (non-climacteric) regulation coexist during the process of climatic fruit ripening. Furthermore the suppression of ethylene in the melons using biotechnology indicated that ethylene did actually control or regulate many aspects of ripening. This was indicated by an increased aroma biosynthesis and degrading mechanism which can be described as features of ripening. Pech et al (2008,p118) conclude their study by stating that as opposed to other fruits, the melon is a good mode of a type of fruit that can be used in examining the role contributed by ethylene in fruit ripening. This is because the melon is composed of both the non climacteric and climacteric attributes. According to Burg and Burg (1961, p179) the role of ethylene in the ripening process has theoretical backing. One of the views is the classical view point that was proposed by Kid and West (1945, p467). According to the classical perspective ethylene is basically a ripening hormone that can be described as a by product of the process of ripening. The by product theory or perspective was verified using an experimental finding which indicated that 0.1pp of ethylene can actually stimulate the process of ripening. In essence the absence of the content of internal ethylene and the level of ethylene production can support the argument that small quantities of ethylene have the capability to induce ripening. In addition this supports the fact that ethylene is produced before respiration, however measurable amounts can be identified only after climacteric begin. The classical theory however leads to the question of the whether or not ethylene can be categorized as a natural hormone for ripening. Conclusion From the above analysis of literature, what is evident is that ethylene plays a significant role in the process of fruit ripening; in addition ethylene is also involved in the development of fruit colour. The paper has examined the views of various authors and the studies that have been conducted in order to determine the role that ethylene hormone contributes in the two areas. One of the crucial findings that can be derived from the review is that exact the role that ethylene contributes to the ripening of fruits is actually no precisely outlined. However based on the various studies that have been conducted, it can be concluded that the presence of ethylene in plants does influence fruit ripening and development of fruit colour. This paper proposes that additional studies should be conducted essentially in the area of non –climacteric fruits. References Adams , P, Barry, C, Giovannoni, J, 2004, Signal transduction systems regulating fruit ripening, Trends Plan science, 9:p331-338. Burg, S and Burg , E,A,1961, Ethylene Evolution and subcelluar particles, Nature ,191;p179. Burg, P, 2004, Postharvest Physiology and Hypobaric Storage of Fresh Produce, CABI, p29. Barry , C and Giovannoni, J,2007, Ethylene and Fruit Ripening , Journal on plant growth regulation,26: p143-159. Kader, A, 2002,Postharvest Technology of Horticultural Crops, University of California, p. 157. Kid ,F and West,C ,1945, Respiratory Activity and duration of life of apples gathered at different stages of development and subsequently maintained at a constant temperature, Plant Physiology ,20;p467-505. Khan, N, 2006, Ethylene Action in Plants, Springer,p152. Mayuoni, L, Tietel, Z, Bhimanagouda, S and Porat, P , 2011, Does ethylene degreening affect internal quality of citrus fruit , Postharvest Biology and Technology,  62, (1); p 50-58 Oetiker , J and Yang, S,2006, The role of ethylene in fruit ripening, Postharvest Physiology of Fruits, p398. Prinsi, B, Simone, A, Fedeli, C, Morgutti,S and Luca, E, 2011, Peach fruit ripening: A proteomic comparative analysis of the mesocarp of two cultivars with different flesh firmness at two ripening stages , Phytochemistry, 72( 10); p 51-62. Pech, J,C , Bouzayen, M, Latche,2008, Climacteric ripening :Ethylene-dependant and Independent regulation of ripening pathways in Melon Fruit,p115-119. Ramina, A, Chang, J, Giovannoni, J, 2007, Advances in Plant Ethylene Research: Proceedings of the 7th International Symposium on the Plant Hormone Ethylene, Springer publishing, p79. Vidhu, A, Sane, A and Pravendra, N,2005,’’Softening in mango (Mangiferaindica cv. Dashehari) is correlated with the expression of an early ethylene responsive, ripening related expansin gene’’, Postharvest Biology and Technology, 38, (3); Pg 223-230 Read More