There that plants are subjected have either direct

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Last updated: May 24, 2019

There exist some abiotic stresses which includesalinity, drought and temperature that affect the growth, survival andreproduction of plants. As a results, plants respond to such unfavorableconditions by physiological, developmental and biochemical ways.

In order torespond appropriately to these changes, it demands expression of stress-response genes. These stress response genes are regulated by a network oftranscription factors (TFs). These include the heat stress transcriptionfactor, abbreviated as HSFs).

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This factor plays an important role in responseof plants to various abiotic stresses. They accomplish this by regulating theexpression of stress responsive genes like the heat shock proteins (Hsps). The stresses that plants are subjected have eitherdirect or indirect effect on their productivity. Some of the abiotic stresseslike high temperature, salinity and drought results in a deadly economic lossin agricultural sector. According to Rodziewicz et al., (2014), theyestablished that there is an estimate of 50% losses in crop yield worldwide asa result of these stresses.

In addition, Edmeades (2009) established thatabiotic stresses that result from either cold, salinity; high temperature or droughthinders crops from realizing their full yield potential.It is a complex phenomenon for plants to respond tothese abiotic stresses because of plants at different development stages can beaffected by a particular stress and therefore, simultaneous occurrence ofstresses can affect the plants, as established by Chinnusammy et al, (2004).Heat stress affect the photosynthetic rate of plants directly and indirectlyhence changing the structural organization and psycho-chemical properties ofthylakoid membrane of the plant, as suggested by Lichtenthaler et al., (2005). Accordingto Sage et la. (2007), there is an increase in the rate of photorespirationwith the increase in heat (temperature) which then results in reduction ofphotosynthesis. Flowing stage in a plant is the most sensitive stagethat is affected by high temperature as high temperatures damage it.

This isbecause of the high level of vulnerability in the event of development of pollen;fertilization and anthesis in a plant which will alter reduce the final yieldof the plant (Kumar, 2015). He found out that for every unit increase intemperature result in a reduction in the plant yield by about 3 to 7% (Kumar,2015). With the increasing incidences of abiotic stresses, ithas necessitated the creation of a new genotype or screen that can be used forthe existing germplasm that is favorable for the changing conditions. Stress Stress can be defined as a change in the environmentthat is sudden and the change can exceed the optimal conditions of the organismand the change result in a change in homeostatic imbalance (Taiz et al., 1991).

Plants that grow under the field conditions experience various environmentalconditions that are exposed to them and these conditions affect their macro andmicroenvironment as suggested by Larcher, (2003). Stress can be caused bydifferent factors including abiotic factors which include variation in temperature,strong light, and salinity among others. It can also be caused by bioticfactors like insects, bacteria, virus among others. Plants can at times face acondition of combination of both biotic and abiotic factors. Yadav et al (2014)found out that abiotic stress is the main agents that cause failure in most ofplants. They found out that they lower the average production of plants byabout 60% which then threaten sustainability and food security.

Abiotic StressThese are non-living factors that affect negativelyplants on a specific environment. These factors influence the environmentalconditions beyond their normal range required by plants hence affectiveadversely the performance of the population of plants. They include extremetemperatures which can be too much heat or freezing, drought, reduction in thenutrients in the soil, too much light and excessive toxicity in the soil. The response of plants to stress depends on the areait was affected by the stress. Several signaling pathways come up due to themolecular response of the plant to any stress. These include RNS or ROS and thehormonal changes which include ethylene and ABA as established by Cramer etal.

, (2010). He also commented on the use of time series analysis in order tostudy multiple phases that relate to stress responses that were important inanalysis that aims at distinguishing between the primary and the secondarystress responses by plants. Some of these mechanisms that can be used torespond to stress include signal transduction, stress perception andtranscriptional activation of stress response genes. Others include synthesisof proteins that relate to the stress and other molecules that can help plantsto cope with adverse environmental conditions. Heat StressAccording to Rao et al (1992), they found out thathigh temperature enhances development in plants and result in abortion offlower leading to a significant loss in the yield of seeds.

They suggested thatthe duration of flowering in plants have a strong impact on the yield of seedsand a rise in temperature result in causes a decline in the yield. Thesefindings were obtained from a study of Indian Mustard seed.  They also agreed that flowering is the mostsensitive stage of a plant and any change in environmental conditions result instress damage. In addition, Cramer et al.

(2010) established that themain cause of the rise in sterility in plants when subjected to heat stress areas a result of the impaired meiosis in both the female and male organs ofplants. It is also due to the impairment of the pollen germination and thegrowth of pollen tube, anomaly in position of style and stigma and disturbancein the process of fertilization among others. According to the research done by Mishra et al. (2011),they reported that in case of a progressive shortfall in precipitation in conjunctionwith high level of evapotranspiration rate that is caused by high heat resultin agricultural drought. Drought adversely affect the growth of plants andtheir development which in turn lower the rate of growth in plants and hencebiomass accumulation. Mishra et al.

(2011) further argued that heat stress isone of the main factors that limit the production of crops in the world. Araus et al., (2002) concluded that heat stress is oneof the main abiotic factors that seriously affect crop productivity worldwide. Hefound out that long term exposure of plants to high temperatures affect theirbiochemical, metabolic and molecular functioning of plants. This have a seriouseffect on various parts of the plant like the leaves, flowers, roots and thebuds hence affect productivity.

Another research conducted by Al-khatib et al. (2004)found out that in case of an increase in temperature, it results in prematuresenescence of plants which can lead to an increased rate of photorespiration. Theyalso observed that there is an increased in the rate of photorespiration withan increase in the temperature.

This in turn lowers the rate of photosynthesis whichin turn affects the yield. 

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