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The Absorption of Organic Phosphate by Rice Plant from Culture Solution

A.H. KHAN
Department of Soil Science, University of Dhaka, Dhaka-1000, Bangladesh.

S. BEGUM
Department of Soil Science, University of Dhaka, Dhaka-1000, Bangladesh.

A. ISLAM
Department of Soil Science, University of Dhaka, Dhaka-1000, Bangladesh.

R. MANDAL
Department of Soil Science, University of Dhaka, Dhaka-1000, Bangladesh.

Abstract/ Executive Summary:

Rice root absorbed about 0.215 and 0.295 mg phosphate directly from Na-phytate and Ca-glycerophosphate, respectively after 8 days of absorption. The amounts corresponded upto 65 and 33 percent of total absorption of phosphate. The rate of absorption increased upto 6 days following by a decreased with time and was influenced by the hydrolizable nature of the compounds. Presence of relatively easily hydrolizable Ca-glycerophosphate resulted its less direct absorption ion in comparison to the less hydrolizable Na-phytate. 0.2% HgCl₂ was effective to prevent phosphate absorption upto 2 days from KH₂PO₄ and Ca-glycerophosphate and upto 4 days from Na-phytate. However, no inhibitory effect due to sterilization of rice root by H₂O₂and C₂H₅OH mixture on phosphate absorption was observed.

Keywords: Absorption, Organic phosphate, Rice plant, Culture solution

Location: Dhaka University, Bangladesh

Start Date:

End Date:

Program Area: Resource Development and Management

Commodity: Soil fertility

Objectives:

To test the direct availability of Ca-glycerophosphate and Na-phytate by IR-8 variety of rice.

Methodology:

Locards, nutirient solution was used with slight modification of 41, 30, 5 and 17.2 ppm nitrogen,Sterile water culture apparatus: The sterile water culture apparatus was made as designed by Islam et. al . A series of bottles were filled with different test solutions, stoppered with rubber corks and were connected to one another by glass and rubber tubings . On each cork one hole was made to introduce the roots into the bottles. The bottles and the glass tubes were autoclaved and cooled before fitting. The bottles were connected in an aseptic environment. The roots of the plants were introduced into the bottles through the hole of the corks and the holes were made air tight with sterile cotton. The number of plant per bottle was one. To aerate the root medium,air was passed through alcohol by a mechanical aspirator. Alcohol prevented the possibility of contamination during aeration.Experimental technique: The experiment was designated in two sets, in one set free hydrolysis of the organic phosphate compounds by the root enzymes was allowed but the uptake of any form of phosphate was prevented by sterilizing the roots with 0.2% HgCl₂. In the other set, the hydrolysis and the uptake of phosphate by roots were both allowed, roots being sterilized with ethyl alcohol and hydrogen per oxide ( 50:50, V:V ) Sampling of solutions was done at every 2 days interval by passing air through the alternate side of the bottles thus pushing a little amount of solution into the best tube. However, before sampling of solutions all the bottles were disconnected. After sampling, the bent tubes were washed with conc. H₂SO₄ and subsquently with sterile water. The bottles were fitted again in place. All of these operations were done in aseptic environment. calcium, iron and chlorine respectively. Potassium di-hydrogen phosphate, calcium glycerophosphate and sodium Experimental technique: The experiment was designated in two sets, in one set free hydrolysis of the organic phosphate compounds by the root enzymes was allowed but the uptake of any form of phosphate was prevented by sterilizing the roots with 0.2% HgCl₂. In the other set, the hydrolysis and the uptake of phosphate by roots were both allowed, roots being sterilized with ethyl alcohol and hydrogen per oxide ( 50:50, V:V ) Sampling of solutions was done at every 2 days interval by passing air through the alternate side of the bottles thus pushing a little amount of solution into the best tube. However, before sampling of solutions all the bottles were disconnected. After sampling, the bent tubes were washed with conc. H₂SO₄ and subsquently with sterile water. The bottles were fitted again in place. All of these operations were done in aseptic environment. Experimental technique: The experiment was designated in two sets, in one set free hydrolysis of the organic phosphate compounds by the root enzymes was allowed but the uptake of any form of phosphate was prevented by sterilizing the roots with 0.2% HgCl₂. In the other set, the hydrolysis and the uptake of phosphate by roots were both allowed, roots being sterilized with ethyl alcohol and hydrogen per oxide ( 50:50, V:V ) Sampling of solutions was done at every 2 days interval by passing air through the alternate side of the bottles thus pushing a little amount of solution into the best tube. However, before sampling of solutions all the bottles were disconnected. After sampling, the bent tubes were washed with conc. H₂SO₄ and subsquently with sterile water. The bottles were fitted again in place. All of these operations were done in aseptic environment. phytate were dissolved seperately in redistilled water to prepare 1 litre 1000 ppm phosphate solutions. 16 ml Analytical technique: Sampled solutions were divided into two portions, (a) for inorganic phosphate and (b) for total phosphate determination. Aliquots of (a) were used directly colour development and that of (b) after digestion with concentrated with nitric and perchloric acid. The method of Mehta et. al. was followed for phosphate determination. The difference between the total and inorganic phosphate was the amount of organic phosphate in the solution. The total uptake and the amount of hydrolysis were recorded from where the amount of organic phosphate absorbed was calculated. The reduction in the total amount of phosphate in the culture solutions was considered as the amount of total absorption. The increase in the amount of inorganic phosphate in the culture solution of the set, where 0.2% HgCl₂ sterilized rice plants were used, was the amount of hydrolysis. Inorganic phosphate absorbed = (Inorganic phosphate initially present + hydrolyzed inorganic phosphate ) – (inorganic phosphate retained in solution after absorption). Organic phosphate absorbed = Total phosphate absorbed - inorganic phosphate absorbed. Before sampling of solutions, to overcome the loss of water during transpiration sterile water was poured into the bottles to bring the volume to 200 ml for the convenience of calculation of absolute amount of phosphate. of each of these phosphate solutions were seperately diluted to 1 litre with modified Locards, solution to get a complete nutirient solution of 16 mg phosphate per litre. Each bottle contained 200 ml of solution and thus contained 3.2 mg of phosphate.

Source of Information: Journal of Bangladesh Academy of Sciences, Vol. 12, No. 2, 121-127, 1988

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

It has been found that rice plants absorbed appreciable amounts of phosphate from both the organic phosphate compounds. Between the compounds, rice plant absorbed relatively more phosphate from Ca-glycerophosphate than that from Na-phytate. However, maximum amount of phosphate was absorbed from the inorganic P compound, KH₂PO₄ No appreciable variation in the uptake of P from KH₂PO₄ by sterilized and non- sterilized roots suggested that sterilization by H₂O₂and C₂H₂OH did not induce any inhibitory effect on the process of P absorption. However, the non- sterilized roots absorbed slightly more P from the organic P compounds than that absorbed by the sterilized roots and it was possibly due to the microbial decomposition of the organic phosphate substrates.

Knowledge Management: Journal