Abiotic Stress It is a stress caused by non-living external conditions like excess salt, water deficit, high light intensities, UV light, high temperature, low temperature or cold stress, excess water or flooding, metal deficiencies or excess, mechanical, hypoxic, anoxic and oxidative stress etc. It has unavoidable negative impact on the plant growth and development and finally on the yield component.
Bacterial Stress It is caused by a release of elicitor from different classes of bacteria (soil, air and water borne) called Microbial or Pathogen Associated Molecular Patterns (MAMP, PAMP). Bacterial Avr proteins are delivered directly into plant systems and inhibit its defense system.
Biotic Stress It is a stress normally caused by living organisms, such as insects, fungi, bacteria, viruses, nematodes, mites and animals. It devastates the growth of crops and crop productivity worldwide.
Drought Stress Deficiency of water for extendable period of time affecting crop productivity.
Flooding Stress It is a stress where excess water imposes deficiency of oxygen, diffusion of gases through soil pores is strongly inhibited by their water content that it fails to match the needs of growing roots.
Fungal Stress It is caused by pathogenic fungi leading to impairment of plant functions. Plants develop polygenic resistance by developing partial resistance proteins (PR).
Herbivore Due to sessile nature, plants are attacked by many herbivores and pathogens.
How do stress proteins help plants to alleviate different types of stresses When plants are subjected to single or a combination of stresses, they develop various mechanisms in response to various stresses, which are complex and integrative? Stress triggers some of the transcriptional and post translational modifications of the proteins. Some proteins like transcription factors trigger downstream gene networks associated with the restoration of homeostasis. Other proteins like ascorbate peroxidase, Catalase and superoxide dismutase help in detoxification of the reactive oxygen species. However, some other proteins participate in protecting the most important macromolecules against denaturation. Thus, stress proteins can alleviate both biotic and abiotic stresses by several different mechanisms.
Insect Stress More than 160 of insect species cause various degrees of damage (affecting both vegetative and reproductive phases) to plants but only in a limited number. e.g. red cotton bug, Helicoverpa etc.
Light Stress Exposure of plant to excess light and U.V. radiations that cause stress and damage the photosynthetic machinery in plants. It is perceived by photoreceptors in plants.
Metal Stress Metals like arsenic, mercury, cadmium and lead are highly toxic at elevated levels. If the cytosolic metal concentration of plant increases, phytotoxicity of heavy metal inhibits transpiration and photosynthesis, disturbs the complete metabolism of plants.
Nematode Stress Programmed cell death of plants caused by parasitic nematodes which enter from soil and forms community bacteria, fungi and insects.
Nutrient Stress Nutrient deficiency occurs when an essential nutrient is not available in sufficient quantity to meet the requirements of a growing plant. Toxicity occurs when a nutrient is in excess of plant needs and decreases plant growth or quality.
Oxidative Stress It is caused by inability of an organism to detoxify the reactive oxygen species.
Phytohormones Plant hormones interact by activating either a common second messenger or a phosphorylation and dephosphorylation cascade in response to stress.
Salt Stress Process of accumulation of more salt in soil that can damage the plant, may also cause by mineral weathering.
Stress proteins Proteins that are produced under biotic and abiotic stress conditions are called as stress proteins. They can protect the DNA, RNA and also proteins under stress conditions. Some of them might also trigger the other gene net works and downstream signaling pathways associated with stress tolerance. Thus, they may restore ions, further maintaining homeostasis; control damage repair and protect the macromolecules (DNA, RNA, proteins).
Stress Metabolic derailment due to environment modulation in plant homeostasis is called stress. These stress factors are interconnected and lead to a series of biological, morphological, physiological and molecular changes leading to the death of plants.
Viral Stress Several different classes of plant viruses are efficient pathogens with great persistence and evolve rapidly through mutation and genetic recombination to prevail over adverse conditions. They can totally devastate the crops.