Biotic stress factors

For a long time, dieback and decline of specific forest species, somewhere in the temperate zone, has been common. Age, climate, or biotic stress factors have frequently been judged to be the principal causes for declines. Again, however, it is difficult to assign responsibility for specific cause and effect. Trees are large and long-lived and their health integrates all the stresses to which they are exposed over time. 

Biotic stress factors due to predation are usually severe in coral reefs whose biota is characterized by rich and diverse fauna and flora. Many of sessile organisms such as sponges, ascidians, soft corals, etc. have had toxins and noxious compounds to protect themselves fi om the predators. These compounds may be important sources for natural products based drugs and medicines [1-3]-... 

On the other hand, and since alkaloids constitute a defense against certain environmental stresses, it is not surprising that the TIA pathway shows induction by several biotic and abiotic stress factors [6, 133-137], Among those, the induction by fungal elicitors has been particularly well characterized, together with the regulation by the plant stress hormone methyljasmonate [5, 9]. 

Agarwal, P.K., P. Agarwal, M.K. Reddy, and S.K. Sopory. 2006. Role of DREB transcription factors in abiotic and biotic stress tolerance in plants. Plant Cell Rep. 25 1263-1274. Alamillo, J., C. Almoguera, D. Bartels, and J. Jordano. 1995. Constitutive expression of small heat shock proteins in vegetative tissues of the resurrection plant Craterostigma plan-tagineum. Plant Mol. Biol. 29 1093-1099. 

The potential would appear to be great for particles lodged on leaf surfaces to interact chemically with either ambient gaseous pollutants or precipitation. Such particles could effectively increase the surface area of leaves available for absorption of gaseous pollutants and, depending on their source, either neutralize or further acidify rain water contacting the leaf surface. Such interactions certainly occur in nature, and may be important in the ultimate response of a plant to complex mixtures of biotic and abiotic stress factors. 

Pterocarpans are a group of modified isoflavonoids occurring in small amounts in legume plants (Fabaceae) and in several other families. They typically act as phytoalexins, protecting plants against pathogens. Unlike most of the isoflavones, pterocarpans are synthesised in response to biotic and abiotic stress factors. Their important precursors are the isoflavones daidzein and formononetin. 

Effect of UV on Productivity of the Southern Ocean. Has ozone depletion over Antarctica affected the productivity of the Southern Ocean There is no easy answer. First, one has to take into account the fact that the drastic decrease of ozone over Antarctica has been reported as recently as 1976, a relatively short time in the evolution of the organisms to develop mechanisms to cope with elevated UV. One of the most vexing problems in studying the effects of UV radiation on productivity, is a dearth of historical data on the level of UV. Without these baselines, normal fluctuations could easily be interpreted as decline in productivity. Second, there is a host of biotic and abiotic factors that play significant roles in governing the productivity of the Southern Ocean (40). Ultraviolet radiation is but one more complicating factor to be considered in an already stressful environment. 

On the other hand, biotic factors include natural interactions (e.g., predation and parasitism) and anthropogenic stress (e.g., the effect of human activity on other organisms). Because of the abiotic and biotic factors, the environment to which an organism is subjected can affect the life functions, growth, and reproductive success of the organism and can determine the local and geographic distribution patterns of the organism. 

Finally, recent research suggests that different types of stress caused either by biotic or abiotic factors activate PPO and POD, thereby stimulating phenolic boactivity [24-27]. 

Orcutt, D.M., and Nilsen, E.T. 2000. The Physiology of Plants Under Stress. Soil and Biotic Factors. Wiley, New York. 

Characterize the biogeochemical processes in marine waters after oil spill. Stress the role of abiotic and biotic factors. 

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