Antitranspirants and their effect on crop

Antitranspirants and their effect on crop

1. Assignment – 2 GUIDED BY Dr . S.S Bhadauria Submitted by OMPRAKASH PARIHAR Roll.no- 20111109 ( M.sc .previous ) Dept . of AGRONOMY COA GWALIOR Rajmata Vijayaraje Scindia Krishi Vishwa Vidyalaya COLLEGE OF AGRICULTURE GWALIOR (M.P.) Anti- transpirants and their effect on crops

2. Antitranspirants are the compounds or the substances applied to the leaves of the plants for the purpose of reducing water loss (transpiration) without causing a momentous change in the various important processes of the plant such as growth and photosynthesis . Antitranspirants are generally classified into four distinct categories:- S tomatal closing type F ilmformingtype R eflecting type Growth retardant

3. The scope of using antitranspirants includes 1 . Under dryland area, to reduce water losses through transpiration 2 . In costly irrigation, for extending the irrigation interval 3 . In areas having poor quality of soil-water or irrigation water, to reduce the uptake of salts 4 . For reducing transplanting shock of nursery plants.

4. There are four principles of transpiration control : 1. By increasing leaf resistance to water vapour transfer by application of materials, which tend to close or cover stomata ( e.g both stomatal closing and film forming type of antitranspirants ) 2 By reducing amount of energy absorbed by leaf surface ( e.g leaf reflectants ). 3 . By reducing top growth of plants ( e.g growth retardants ) 4. By increasing air resistance to water vapour transfer by shelter belts/windbreaks

5. Stomata closing type: Most of the transpiration occurs through the stomata the leaf surface. Some fungicides like Phenyl mercuric acetate (PMA) and herbicides like atrazine in low concentration serve as antitranspirants by inducing the stomatal closing. PMA was found to decrease transpiration to greater degree than the photosynthesis in a number of plants. Stomatal opening is regulated by various sensors like, water , C O, light and hormones. The opening is strongly controlled by hydro-active mechanism, while other sensors are lıydro -passive and is mediated through relative water content (RWC) of guard cell chloroplast.

6. Film-forming type : Foliar spray of waxy or plastic emulsions such as mobileaf . hexadeconol and silicone produce an external physical barrier outside the stomatal opening to retard the escape of water vapour through stomatal opening. The film so formed should have more resistance to the passage of water than to that of carbon dioxide. Film type antitranspirants , which provide selective type of permeability barriers to water vapours and carbon dioxide diffusion in the required directions, have not yet been found so far .

7. Increasing leaf reflectance type: White reflecting materials such as whitewash or kaolinite % spray form a coating on the leaves and increase the leaf reflectance (albedo). By Terecting the large amount of radiation, Application of 5 per cent kaolin spray has been found to reduce transpiration losses markedly. Growth Retardants These chemicals reduce shoot growth and increase root growth and thus enable the plants to resist drought. They may also induce stomatal closure. Cycocel is one such chemical uselul for improving water status of the plant.

8. EFFECT OF ANTITRANSPIRANTS ON CROP PRODUCTION:- Antitranspirants are used to reduce the losses of water through transpiration, so that limited amount of available soil moisture can be used for completing the life cycle of crop plants . Antitranspirants along with slowing the rate of transpiration reduces the photosynthesis efficiency of crop plant due to less uptake of carbon dioxide through narrowed aperture of stomata, relatively less permeability of carbon dioxide through the film and rise in leaf temperature. Reduction in transpiration as well as photosynthesis after treatment with antitranspirants is well documented in the literature.

9. Limitations of antitranspirants :- May reduce the rate of photosymthesis May increase the leaf temperature by reducing evaporative cooling Interaction of climatic factors with antitranspirants reduces their effectiveness for longer duration Marginal cost may be more than marginal returns May produce toxic effects on leaves.

10. Effects of antitranspirants in field crops Antitranspirants in wheat In wheat cultivar DWD-1006, irrigation,mulch and antitranspirant application were found to improvise the growth, yield and yield contributing attributes and cost of cultivation . Five irrigations at different critical stages increased the various growth parameters , mulched treatment provide highest total dry matter production per plant and treatment with antitranspirant , kaolin along with five irrigations were found to increase the dry matter accumulation, grain yield and also offers highest gross return and cost of cultivation (Brahma et al., 2007 ). Antitranspirants in maize Antitranspirant application with alachlor @ 20mg/ litre in maize plants was reported to be most effective in reducing the rate of transpiration and partially hindered the stomatal opening

11. Antitranspirants in barley Pre and post inoculation sprays of film- forming type of antitranspirants viz., Nu- film P, emerald and vapor gard results in greater decline in powdery mildew infection of barley seedlings, significantly. For better results, mixture of 2% vapor gard along with 1Mm alpha- difluoro methylornithine (DFMO) were found to be the best against the fungus and applied before one day to inoculation with the fungus (Walters, 1992). Antitranspirants in soybean Foliar application of antitranspirants , applied at 60 days after planting i.e. at flowering stage and seed formation stage had very positive effects in growth, yield and yield attributing traits of soybean under limited irrigation, Antitranspirant , kaolin @6% were found to be the most effective that significantly increased the stem height, stem diameter, node number, number of pods, number of seeds per plant,