**3. Abiotic factors (abiotic stress)**

Climate is changing globally nowadays because of extensive crucial human activities, while Abiotic stresses are a direct consequence of climate change. Whereas as it's foreseen to be more breathtaking increase then the average universal temperature [68]. Abiotic factors are of particular importance in regard to sustainable cotton production, because from sowing to harvest all the development stages of cotton plant depend upon abiotic factors for optimum level to grown normally. Abiotic stresses (extreme temperature, relative humidity etc.) cause distress to cotton crop and resulted in substantial decrease in yield of cotton and damage the lint quality [69, 70]. Yield loss in cotton due to the influence of abiotic factors is around 50% [13]. The major particular characteristic of abiotic tensions is their occurrence and acquaintance at the same time, simply they act same upon plant growth and plant defense behaviors that makes it more complex [71]. Keeping in view the roles of abiotic factors (abiotic stresses), here, we will analyze and summarize the effect of those in relation to sustainable cotton farming system.

## **3.1 Temperature impact**

All crops depends upon the optimum temperature for the proper growth and development, so temperature is a chief dynamic for farming of different crops. The growth rate of cotton crop mainly dependent on the temperature, although the cotton plant is basically from tropical origin and can survive in high temperature environments but extremely hot climatic situation resulted in reduction of cotton yield [72]. Extreme temperatures either its cold or hot can ultimately affect the growth or development of cotton crop and could delay or even reduce the cotton production. Minimal changes from optimal conditions could severely effect plant growth, even 2–3°C increase from optimum temperature reduce plant growth and cause decline in yield and biomass along with increase of fiber micronaire [69]. High temperature directly or indirectly affects the growth and development of cotton and leads to drought stress because of higher evaporation from the fields. A study from Arkansas USA proposed the negative correlation between high temperature ranges and cotton production [73]. They found that the high temperature unswervingly disturbs the biology (vegetative ad reproductive stages) of cotton. This influence eventually leads to increase the production of more vegetative portion and lowering the reproductive portion of cotton plants [74]. Particularly reproductive stage of cotton crop also be strongly influenced by some other heat stress related other severe effects; in general the maturing of reproductive parts could be impacted more and cause reduction in the yield. If the temperature is higher than optimum or regular temperature, the first square formation or flowering start and first boll formation or boll opening rate decreased. Retention phase for the squares and bolls mostly decreased under high temperature [75]. Same as high temperature, low temperature also badly effect cotton growth. The development of cotton could be delayed by extreme drops of temperature under 11°C that further resulted into prolonged growth period [16]. Yadav discusses plant reactions to cold stress as well as physiological reactions and strategies for cold tolerance [76]. While at present the main focus of authors for sustainable cotton production is on high temperature under changing climatic situations.
