Water Culture




Culture Experiments

German botanist Julius Sachs ( 1860)  demonstrated  for the first time that plants can be reared from seedling state to mature state  in nutrient solution even in the absence of soil. 

 Most of the minerals present in the soil can enter plants. With the help of sensitive techniques, concentration  as low as 10-⁸ g/ml can be detected. Mor  than  sixty minerals present in soil have been recorded  in plants. Some plants accumulate  heavy and toxic materials, e.g., Astragalus  ( selenium), Phacelia sericea ( gold) plants growing near nuclear sites ( radioactive strontium). 







There are experiments involving  raising of plants on artificial  media having nutrients. Water used in preparing culture solution  is twice distilled in glass containers. Salts are chemically  pure. The  solution containing  the various  mineral elements in proper proportion is called normal or balanced nutrient solution.The element of which deficiency symptoms are to be studied is made deficient in the solution. The growth of such plants is compared with the growth of control plant growing in balanced nutrient solution. If the changes in characters appear, those characters can be  attributed  to the deficiency of that particular element. Seedlings are reared either directly in such  solution  ( solution  or water culture) or in earthen pots having sterilized  sand ( sand culture). 







These experiments are useful in knowing:__ 

(1)  Essentiality of mineral nutrients

2) Role of an essential  element in body structure and physiology. 


4) Toxicity due to excess  of an element 

5) Interaction  of different  elements. 

6) Role of a nonessential  functions  element. 




Precautions 

1) Great care is taken to avoid contamination  of the nutrient solution  as far as possible, particularly  with the trace elements which are often present as impurities in container's  wall or water used in making nutrient solution or reagents being used. This does not give correct result about the essentially  of a mineral element. Thus only purified water and mineral nutrients are used.

2) The containers are covered with black paper to prevent the growth of algae and phototropic reaction of roots to  sunlight.  

3) Adequate aeration of nutrient solution  is essential  to supply oxygen  to roots to obtain optimum  root growth and mineral uptake. 


4) For studying  the effect of microelements, cotyledone and other organs,  containing  reserve food are removed because  they are rich source of microelements.





Determination  of Essentially of Minerals  Elements: 

A number of method  are employed  to study the mineral requirements  of plants and to determine  the  essentiality of a mineral element. In  all these methods, plant is grown in a nutrient solution in the absence of soil. Hydroponic growth system, nutrient film growth system  and aeroponic growth system are such methods for growing plant without soil in nutrient solutions which composition  and pH can be automatically  controlled. 

In a hydroponic system, the roots are immersed in the nutrient  solution  and air is bubbled through  the solution . In nutrient film technique, plants are grown in a tube or trough placed on a slight incline. The roots are continuously  bathed with thin film of recirulating aerated nutrient solution with controlled pH and nutrient contents. In aeroponics roots are suspended in the air over the nutrient  solution  which is whipped  into a nutrient  mist ( cloud of moisture in the air) by a motor driven rotor. In all these methods, plants are cultured  in a soil free, defined or balanced  nutrient solution. 

Mineral and Non_ Mineral  Elements:

Essential  elements  derived from soil are termed as mineral elements. Essential  elements derived  from air or water are called as non mineral  elements. In aquatic  habitats  as well as in soil solution,  mineral elements occur dissolved in water. It is also available  from air. Nitrogen is present  in abundance  in the air as a  nonmineral  element but plants usually  obtain it from soil as nitrate or ammonium ion. The two are formed by the process of fixation of atmospheric nitrogen though   a small quantity can also come from weathering  of rocks. Chlorine is got as a mineral  from soil but can also be obtained  from the atmosphere. Some sulphur is also absorbed  from the atmosphere  where it is present as a pollutant  in the gaseous state  of sulphur dioxide. 



Mineral Elements. P,K, S, Mg, Ca, Fe, Zn, Mn, B, Cy, Mo, CI and N.



Non _ Mineral Elements: C, O, H, and N 









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