Plant Growth : Nutrients

Essential elements

Carbon 碳 ( C ) , Hydrogen氢 ( H ) ,& Oxygen 氧 ( O).

Essential elements ( Arnon and Stout, 1939) :

-        A plant must be unable to complete its life cycle in the absence of the mineral element.

-        The function of the element must not be replaceable by another mineral element.

-        The element must be directly involved in plant metabolism.

Macronutrients ( 大量元素):
Primary : Nitrogen氮(  N ) , Phosphorus磷( P ) , Potassium鉀( K )
Secondary : Calcium钙( Ca ) , Magnesium鎂( Mg ) ,&  Sulfur硫( S ).         

Macronutrients are consumed in large quantities.  They are present in plant tissue in quantities from 0.2% - 4%.

Micronutrients ( 微量元素 ) ( Trace elements ) :

Chlorine 氯( Cl ) , Iron 铁( Fe ) , Manganese 锰( Mn ) , Boron 硼( B ) , Zinc 锌( Zn ) , Copper 铜( Cu ) , Molybdenum 钼( Mo ) & Nickel 镍( Ni ).  

Micronutrients are present in plant tissue in small quantities.

Beneficial Elements :

Silicone 硅 ( Si ) ,&  Cobalt 钴 ( Co ).   

Beneficial elements are those that  :

-        can compensate for toxic effects of other elements or

-        may replace mineral nutrients in some other less specific function e.g. the maintenance of osmotic pressure.

The omission of beneficial nutrients in commercial production could mean that plants are not being grown to their optimum genetic potential but are merely produced at a subsistence level.

The beneficial elements have not been deemed essential for all plants but may be essential for some.

 

e.g. Cobalt is essential for nitrogen fixation in legumes. It may also inhibit ethylene formation ( Samimy, 1978 ) and extend the life of cut roses ( Venkatarayappa et al., 1980 ).

e.g. Silicon is deposited in cell walls, has been found to improve heat and drought tolerance and increase resistance to insects and fungal infections. Silicon can help compensate for toxic levels of manganese, iron, phosphorus and aluminum as well as zinc deficiency.

Plant Growth : once a mystery

It is like a mustard seed, which is the smallest seed you plant in the ground. Yet when planted, it grows and becomes the largest of all garden plants . . .

Mark 4 31-32 ( NIV )

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From a tiny seed, plants are capable to grow to a majestic size.

World largest single stem tree, by volume, is a Giant Sequoia ( Sequoiadendron giganteum ), nicknamed General Sherman, stands 83.8 m tall, and the trunk alone is estimated to weigh over 1,814 metric tonne; is grown from a seed not more than 5mm in length !

How does plant gain its mass ? What caused them to grow ?

Man had since awed by the miraculous growth of plant…   Plant seems to be simply emerged from the earth. Of course some suspected the earth provided the substances for plant growth, as did Aristotle, but what exactly ?

Jean Baptiste van Helmont, in 1648 published in his book Ortus medicinae an experiment he performed on a willow tree planted in a pot for 5 years. He weighted the young tree, soil and the water he added. After 5 years, the plant gained about 164 pounds, the amount of soil remain relatively unchanged. Thus, he deducted that the tree’s weight gain had come from water.

Today, we already know that plant’s mass consists of about 80% water, 19% organic matter, and 1% minerals.

Through a process known as photosynthesis, green plants and certain other organisms transform light energy into chemical energy. Water, carbon dioxide, and minerals are converted into oxygen and energy-rich organic compounds.

At the same time, plants rely on soil for supplying water and mineral elements. Mineral elements are essential and beneficial for optimum plant growth.