IN THE NUCLEIC ACIDS. PROTEINS AND AMINO ACIDS IN THE DEVELOPING' MANGO BUDS

Jililian J. Plant Physiol., Vol. XXVI, No.4;'l'P. 378..,..384 (December 1983)

SEASONAL CfIANGES IN THE NUCLEIC ACIDS. PROTEINS AND AMINO ACIDS IN THE DEVELOPING' MANGO BUDS

R.M. PANDEY AND P.R. NARWADKAR Division of Horticultu),e and Fruit::re\;;~QIogy

IndianAgricqItural Research :Institu\e, New·D~bi-lIOOl:z.

(Reeeiyed : Ma!cb 22, 1983)

SUMMARY

The.. seasonal· changes ip Jf,bol.luclj:ic .. ~id. 4~ydbOJlUeJeU: .acid, total and soluble protei~s and TeA soluble amin9.1!1cCi€l' ton'tent ofc::1he developing m~~o"buds of Dashehari (alternate bearer) and Bangalora (regular bearer) varieties were studied. The bud samples were taken from three major flushes produced viz., March, July and September at monthly intervals. In general, there was a slow increase in the levels of different metabolites with the development of the buds. In March/April flush of Dashehari and post-harvest flushes of Bangalora, the levels of RNA, DNA and soluble proteins content of the buds increased rapidly during October, November which was the peak period of the fruit bud differen­ tiation. A slight decrease in the content of the insoluble proteins and the total amino acids was registered during this period.

INTRODUCTION

The alternate bearing is a serious problem in the mango cultivation, which has attracted the attention of several research workers in the country. The physiological maturity of the shoot has been considered to have relation whh the flowering behaviour of this crop. Earlier, the research workers concent­ rated their efforts in finding out the chemical composition of shoots and their relationship, if any, with the :flowering of the shoots. Suryanaryana (1978) has emphasised the changes in the contents of nucleic acids, porteins and amino acids in the shoots of 'on' and 'off' year mango shoots in relation to the :flower­ ing behaviour of some mango varieties. Such studies were lacking for the terminal mango buds wherein actual fruit bud differentiation (FBD) takes place. Therefore, the present study was undertaken.

MATERIALS AND METHODS

NUCLEIC ACIDS, PR.OTEINS AND AMINO ACIDS IN MANGO BUDS 379

of Horticulture and Fruit Technology, Indian Agricultural Research Institute, New Delhi. Two varieties viz., Dashehari (alternate bearer) and Bengalora (regular bearer) were selected for this study. The shoots of different flushes of both the varieties were tagged after their emergence. In case of Bangalora, the ­ shoots periodical1y gave new extension growth and therefore, such newextens­ ion growth was considered as the new flush. The bud samples from the shoot tips were taken at monthly intervals. The sampling was done for three major flushes viz., March, July and September flushes. From these bud samples, the estimation of various metabolites viz., nucleic acids, proteins and amino acids was carriod out. The nucleic acids were estimated by the method described by Ogur and Rosen (1950). The insoluble proteins were estimated as per the methcd given by Mehl (1944) and further described by Lawry et a/I (1951) by using the Biuret reagent, while the soluble proteins were estimated by the method adopted by Lawry et a/I (1951). The values for the total proteins were computed by adding the respective values of soluble and insoluble proteins. The free TeA soluble amino acids were estimated as per the method given by Moore and Stein (1948).

RESULTS AND DISCUSSION

RNA Content

The data illustrated in Fig 1 reveals that, in general, the content of ribonu­ cleic acid (RNA) increased with the development of the buds. The rise in RNA levels in the buds of March/April flush of Dashehari variety showed a distinct peak in November, which was also the period of FBD. In this case,

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380 R.M. PANDEY AND P.R. NARWADKAR

the rise in RNA content was steady and slow upto September and thereafter, the levels rose rapidly, attained the peak value in November followed by a slight reduction during December. On the contrary. buds of Iuly and September flushes of Dashehari did not show any distinct peaks of RNA content, although there was slow and steady rise in its content.

In Bangalora variety, an increase in the RNA content of the buds taken from different flushes was observed. The March flush of Bangalora variety was not available upto December, as it was not produced in sufficient quantity to study the levels of the metabolites upto December. It was produced in traces and most of the flush gave secondary extension. The July and Septembet flushes showed an increase in the levels ef RNA in their buds. In july flush, the peak levels were attained in November, whereas in September Hush, an increase in RNA

content of the buds was found till December.

DNA Content

In general, DNA content of mango buds increased with an advancement of their age in both the varietks (Fig. 2). The increase in the DNA content of

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Fig. 2. Quantitative changes in DNA content of mango buds.

the buds of March/April flush of Dashehari during the months of October­ November and December appeared to be more pronounced when FBD takes place.

Total Protein Content

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flush of Dashehari, the total protein content of the buds· was always more than those taken from other two flushes. In Bangalora variety, the buds ftom July flush had more total protein content than those taken from other two flushes.

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Soluble Protein Content

The data reveal (Fig.4) that there was an increase in the soluble protein content of the buds in both the vaneties. In March/April flush of Dashehari, the increase in the soluble protein content of the buds was more rapid than of other two flushes and showed a peak during November. In Bangalora variety,

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the buds taken from July and September flush showed an increase in their levels of soluble proteins.

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Total Amino Acid Content

In the buds of March/April flush of Dashehari, a rapid increase in the levels of total amino acids was found until September and thereafter. a slight decrease was observed till November followed by an increase again in December. (Fig. 5). The levels of March/ April flush of Dashehari were always more than those taken from July and September flushes, though a slight increase in its content was found in case of latter two flushes.

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Fig. 5. Quantitative changes in total amino acids content of mango buds.

In Banxalora variety, in the buds of the March/April and September flushes, the levels of the amino acids in the buds increased to a smaller extent. But in the buds of July flush of this variety, this metabolite increased till Septem­ ber, decreased during November and again increased during December.

383

NUCLEIC ACIDS. PROTEINS AND AMINO ACIDS IN MANGO BUDS

and September flushes increased rapidly during October-November. These post-harvest flushes of Bangalora can produce flower, whereas in Dashehari variety it is not the case. If levels of metabolite of the post, harvest flushes of Dashehari can be increased faster during October-November. then their possibility to differentiate into fruit buds might increase. Suryanarayana and Rao (1978) noticed an increase in the levels of metabolites, viz., sugars, proteins etc. in the shoot of Mulgoa variety of mango after it was sprayed with Alar and Cycocel each at 5000 ppm. Further work on the induction of flowering on the post-harvest flushes of Dashehari variety by chemical mani­ pulation of the metabolites in the shoot tips is needed.

During the transformation of the vegetative buds to the reproductive ones, more energy is required which is provided by the immense metabolic activities during this period. During the period of FBD in mango, i.e., during October­ November, the levels of nucleic acids and soluble proteins in the differentiating buds were increased faster and compratively negligible changes in the content of these metabolites in the shoots tips of non-differentiating shoots of Dashehari mango, clearly indicated that it was the physiological state of the shoot, which brought such metabolic changes causing differentiation of the buds in one case and keeping them in vegetative state in the other. Rao and Shrinivasan (1971) noticed that the RNA and DNA in the reproductive buds of Anab-e-Shabi grape was more than the vegetative buds. Similarly. an accumulation of proteins in the differentiating apricot buds was recorded by Labedeva (1972). The results obtained in the present study are in conformity with those reported by these workers. The decreased level of total amino acid content of the different­ iating mango buds during November indicates their faster utilizatiori in the formation of soluble proteins during this period.

ACKNOWLEDGEMNT

The financial assistance in the form of Senior Fellowship provided to the author during the course of investigation by Indian Agricultural Research Iastitute, New Delhi is gratefully acknowledged.

REFERENCES

Lebedeva, T.A. (1972). Organogenesis of apricot Hower buds and location of certain substances therein. Nauchnye Trudy, Kubankii Universitet No. 147 : 110-18.

Lawry, O.H., RoseJrough, N.J., Farr, A.L. and Randah, R.J. (1951). Protein measurement with Folin-phenol reagent. J. Bioi. Chem., 193 : 265-76

Mehl, J.W. (1944). The biuret reaction of protein in the presence of ethylene dycol. J. Bioi.

384 R.M. PANI¥Y AND P.R. NARWADKAR

Moore, S. and Stein, W.H. (1948). Photometric ninhydrin method for use in the chromato­ graphy of amino acids. J. Bioi. Chem.,176: 367-88.

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Ogur, M. and Rosen, G. (1950). The nucleic acid of plant tissue. The extraction and estimation of deoxypentose nucleic acrd and pentose nucleic acid. Arch. Biochem. Biophysics.,

25 : 262-76. j /

Rao, V.N.M. and Srinivasan, C. (1971). Nucleic acid composition in the developing buds and and petioles of grapes cv. Anab-e-Shahi Viti., 10: 210-17.

Suryanarayana, V. (1978). Seasonal changes in ribonucleic acid and protein contents in mango shoots in relat~on to flowering. Plant Biochem. I., S : 9-13.