J. Biosci., Vol. 3 Number 3, September 1981, pp. 249-257. Printed in India, Effect of nitrogen, phosphorus and potassium deficiency on the uptake and mobilization of ions in Bengal gram (Cicer arietinum) B. K. DAS* and S. P. SEN Department of Botany, Kalyani University, Kalyani 741 235 MS received 21 November 1978; revised 12 February 1980 Abstract. Nitrogen, phosphorus and potassium deficiency reduced the uptake of 32 P- phosphate, 35 S-sulphate, 24 Na-, 42 K-, 45 Ca-, 54 Mn-, 59 Fe- and 65 Zn- by Cicer arietinum (Bengal gram) cv B-75. Root length, leaf area and dry weight of the tissues were also reduced. Since in several cases, the total contents of the radio nucleides both on per plant and per unit dry weight basis were curtailed, the decrease in uptake of several ions cannot be entirely due to reduced growth rate. The reduction in 32 P-phosphate uptake was more severe with nitrogen deficient plants than that in phosphate deficient ones; potassium deficient plants, however, took up 42 K- as avidly as the control plants. Simultaneously the uptake of 35 SO 2 4 and other cations was affected particularly by nitrogen deficiency. The distribution of radionucleides between the root and shoot portions was also disturbed in several cases by deficiency conditions. The radionucleides taken up accumulated in the young regions as in the case of pea and other dicotyledonous plants. Mobilization of 32 P and 35 S in the reproductive plants was most markedly affected by nitrogen and potassium-deficiency. Keywords. Nitrogen; phosphorus; potassium; deficiency; ion-uptake; mobilization; Cicer arietinum. Introduction The uptake of ions by plants is known to be affected by their deficiencies (Salisbury and Ross, 1974); however, it is not clear how the deficiency of one element affects the uptake of another element. We describe here, some of our observations concerning the effects of three different levels of nitrogen, phosphorus and potassium on the uptake and mobilization of phosphate, sulphate, sodium, potassium, calcium, iron, zinc and manganese ions using radipactively labelled elements in each case. The plant used was Bengal gram (Cicer arietinum Linn.), which constitutes an important protein source in the diet of a large section of the Indian population and on the mineral nutrition of which there is very little research reported (Shivraj, 1978). Materials and methods Bengal gram (Cicer arietinum L.) cv. B-75 was obtained from the Kalyani Seed Farm, Kalyani. The plants were grown in sand culture with three different levels of nitrogen, phosphorus and potassium in porcelain crocks or Brite high density * Present address: Central Sericulture Research Institute, Berhampore 741 001. 249
250 Das and Sen polythene buckets. The normal mineral solution used for growth of plants contained the following in g/1 : NaNO 3 7.37; Na 2 HPO 4.12H 2 O 2.04; K 2 SO 4.1.50; MgSO 4.7H 2 O 1.01; CaCl 2.2H 2 O 0.30; and traces of micronutrients; ph 6.8. Solutions were applied to each pot once a week. To obtain deficiency condition, the amounts of nitrogen, phosphorous and potassium in the nutrient solution were reduced to l/9th of this level. Plants were fed with the radioactively-labelled ions through their roots for 3 h. For anion uptake, young vegetative (4-5 week old) or mature plants (10 week old) in fruiting condition were allowed to take up phosphate- 32 P(5 µci/ml) or sulphate- 35 S (6 μci/ml) from the nutrient solution. For cation uptake, the following elements were applied as their chlorides. 24 Na(10 µci/ml), 42 K(12 µci/ml), 45 Ca(5 µci/ml), 54 Μn(5μCi/m1), 59 Fe(7 µci/ml) and 65 Zn (5 μ Ci/ml). After the experiment, the roots of the plants were washed first in tap water, then in phosphate buffer containing the same salt in the non-radioactive form and finally with distilled water. The plants were divided into two groups. The aerial parts of one group were detached from the roots, and exposed to x-ray films for autoradiography. The root and shoot tissues of the other group were separated, dried,.powdered and radioactivity measured with an end-window counter.for soft β-emitters like 35 S and 45 Ca, counts were taken in saturation thickness. Results Growth Deficiency conditions affected the growth of the plants as indicated by decreased fresh and dry weights. Although shoot height was only slightly affected, root length, branch number and leaf area were markedly reduced. Fresh weight was very much affected in the case of nitrogen-deficiency both in the shoot and in the root tissues. Dry matter accumulation, per gram fresh weight was minimum in the case of nitrogen deficiency, in which case water content was also maximum (table l). Ion-uptake Anion uptake: Phosphate Deficiency of nitrogen, phosphorus and potassium reduced.the uptake of 32 P-phosphate by C. arietinum to a very large extent; the effect was most marked in case of nitrogen deficiency where the plants could take up only about 28% of the 32 P taken up by the normal, nutritionally sufficient plants (table 2). This was followed by potassium and phosphorus deficiency where the uptake was curtailed by about 57%-64%. The 32 P-content per unit weight of shoot and root tissues also revealed largely similar trends. The 32 P- content of the root tissues was always higher than that in the shoot tissues; deficiency conditions however, did not alter the pattern of 32 P-distribiition between the root and shoot tissues (table 1). Sulphate Very similar trends were noted in the case of [ 35 S]-sulphate uptake (table 2). However, in the nitrogen-deficient plants, the roots retained a larger share of the 35 S taken up than the non deficient, control plants, where 35 S was practically evenly distributed between the shoot and the root tissues. The shoot of
Effects of nutritional deficiency 251 Table 1. Effect of nitrogen, phosphorus and potassium-deficiency at the 1/'9 level of supply on the growth of Bengal gram. plants sown on October 24, 1970. a Age of plants 34 days; b Age of plants 68 days. * Significant at P=0.05; ** Significant at Ρ=0.01 Table 2. Effect of deficiency of nitrogen, phosphorus and potassium on the uptake and distribution of 32 P-phosphate and 35 S-sulphate in Bengal gram. 40-Day-old plants were used.
252 Das and Sen phosphorus and potassium deficient plants received a larger fraction of the 35 S taken up than the root. Cation uptake Sodium Deficiency of nitrogen and potassium markedly reduced the uptake of 24 Na, the degree of reduction being 60% and 50%, respectively. In the case of phosphorus deficiency however, the uptake was not much affected (table 3). The distribution of 24 Na between the shoot and the root tissues was also influenced by deficiency conditions; in the case of phosphorus and potassium deficiency, the roots retained a much larger fraction of the 24 Na taken up, but in the case of nitrogen deficiency, opposite trends were recorded. Per unit weight of tissue, however, the effects of nitrogen deficiency on 24 Na content were detectable only in the root tissues; in the case of phosphorus deficiency, unit mass of root contained at least 40% more of 24 Na than in the control. The 24 Na content per unit weight of the shoot in the case of phosphorus and potassium deficiency was decreased by 50% or more (table 3). Potassium The effect of nitrogen deficiency on 42 K uptake was most striking where the reduction was of the order of 40% (table 3). In the control, the 42 K taken up was practically equally distributed between the shoot and root tissues; but under deficiency conditions, the shoot received 3 to 6 times the amount present in the root tissues. In phosphorus and potassium deficient plants, the shoot possessed 46 to 78%, more of 42 K than in the non-deficient plants. The 42 K content per unit tissue weight however, was only twice the amount detected in the control. On per unit weight basis, the root tissues, particularly in the case of potassium deficient plants contained 65% less of 42 K. Nitrogen and phosphorus deficiency reduced the potassium content per unit weight of root tissue to the extent of 35% in both cases. Calcium The deficiency of nitrogen reduced the uptake of 45 Ca to the largest extent, the amount taken up was even less than one-half of the nutritionally sufficient plants. In the case of phosphorus and potassium deficiency, uptake was reduced to about two-thirds. The shoot was more affected than the root, the former possessing only one-third of the total 45 Ca taken up (table 3). The distribution of 45 Ca per unit weight of shoot and root tissues, however, was decreased only to a small extent. Manganese 54 Mn uptake was curtailed by more than 50% by the deficiency of each of the three elements studied; here also the effect was most prominent in the case of nitrogen deficiency (table 3), where the curtailment was of the order of 70%. 54 Mn taken up by the non-deficient plants was distributed between the shoot and the root tissue in the ratio of 2:3; but in the nitrogen deficient plants, the shoot and root shared almost equally the 54 Mn taken up. The root possessed only 25 % to 45% of the 54 Mn found in the non-deficient control. The 54 Mn content per unit weight of shoot and root tissues was least in the case of phosphorus deficiency. Zinc Nitrogen deficiency also reduced the uptake of 65 Zn most; this was true for both shoot and root tissues (table 3). In the case of phosphorus and potassium
Effects of nutritional deficiency 253 Table 3. Effect of deficiency of nitrogen, phosphorus and potassium on the uptake and distribution of 24 Na, 42 K, 45 Ca, 54 Mn, 65 Zn and 59 Fe in Bengal gram. 37-Day-old plants were used. deficiency, the plants suffered almost to the same extent. Irrespective of deficiency conditions, the roots possessed more of 65 Zn than the shoot tissues. Iron The uptake of 59 Fe was almost equally affected by nitrogen and potassium deficiency (table 3). In the phosphorus deficient plants, the roots contained the largest amount of 59 Fe. The 59 Fe content per unit weight of shoot tissues was least in the case of potassium deficiency and highest among the deficient plants in the case of phosphorus deficient roots.
254 Das and Sen Mobilization of ions The 32 P taken up by Bengal gram, as in the case of pea (Biswas and Sen, 1959) was first transported to the apical region and then moved downwards into the lower leaves, older leaves receiving smaller amounts. Deficiency conditions influenced the distribution pattern more strikingly when the plants had flowered and fruited. 32 P was found to accumulate largely in the apical bud and the young leaves, irrespective of deficiency conditions; when the plants flowered, the accumulation of 32 P in the first pod which was the youngest, however, was reduced considerably under deficiency conditions (table 4). The severity of the effects was much less in Table 4. Effect of deficiency of nitrogen, phosphorus and potassium on the distribution of [ 32 P]-phosphate and [ 35 S]-sulphate in the pods and adjacent leaves of Bengal gram.
Effects of nutritional deficiency 255 68-Day-old plants were used. the third pod. This distribution pattern was, however, not correlated with that observed in the leaves subtending the pods. Thus nitrogen-deficiency effects were more marked in the leaves subtending the lower and the more aged pods than the leaves subtending the first pod. Phosphorus deficiency had almost similar effects in the case of the leaves subtending the first and the third pods. On per unit weight basis, the effects of deficiency were much less prominent; in some cases, no sign of deleterious effect was discernible. In the normal plants, 35 S was well mobilized. The deficient plants had a relatively slow rate of uptake and mobilization of 35 S. But the shoot apices and the young leaves invariably retained a larger share. Deficiency effects on mobilizetion of 35 S in the fruited plants were not as prominent as in the case of 32 P. The 35 S- content of the pods was curtailed by no more than 25%. The effect on the first pod, although not very pronounced was the most marked. In the subtending deficient leaves, however, 35 S content was reduced in all cases, the effect of potassium deficiency being most prominent. Deficiency of nitrogen did not help,the distribution of 24 Na in all the leaves. The phosphorus and potassium deficient apical regions accumulated more of 24 Na. Old leaves situated near the base of the plants were only slightly radioactive. 42 K did not reach the leaflets of the lower leaves during the three-hour uptake. The distribution patterns in phosphorus.and potassium deficient plants did not significantly differ from that of control plants. Much of 45 Ca taken up was located in the stem and the apical region in the control and deficient plants.
256 Das and Sen Phosphorus deficiency improved the mobilization of 54 Mn, but mobilization was reduced considerably in the case of potassium deficiency. Mobilization of 65 Zn was also vastly improved under phosphorus deficiency. Accumulation of 65 Zn in the apical region was not affected by any deficiency condition. The mobilization of iron was improved under deficiency of potassium, although the amount of 59 Fe taken up was less than that of the control. The potassium and phosphorus deficient plants accumulated a much larger amount of 59 Fe in the apical regions than in the control. Discussion It has been observed that except in the case of potassium, the uptake of all the ions studied was decreased in the plants deficient in nitrogen, phosphorus and potassium. This reduced uptake may be due to: (i) decreased surface area of the root system, (ii) reduced leaf area, (iii) reduced availability of metabolic energy for ion uptake and (iv) partial inhibition of the synthesis of the carriers required for transport of ions across membranes or their structural alteration resulting in an impairment of functional efficiency. The marked reduction in root length (table 1) would result in a decreased surface area of the root system. The leaf area was reduced by about 40% or more; this would result not only in reduced photosynthesis but also in decreased ion uptake, since the effective area of evaporation per plant was also reduced. Although very little is known about deficiency effects on transpiration, it may be of interest to mention here that Atkinson and Davison (1972) observed a decrease in the rate of transpiration due to phosphorus deficiency. According to Graham and Ulrich (1972), permeability of root to water is greatly decreased in potassium deficiency. Das (1974) and Das and Sen (1974) observed an inhibition of respiration and photosynthesis, particularly due to deficiency of nitrogen and phosphorus; this would reduce the availability of metabolic energy for ion uptake. Das (1974) and Das and Sen's (1971) observation that nucleic acid and protein synthesis is inhibited by deficiency conditions may suggest that the synthesis of protein-type carriers required for ion-uptake may be inhibited by mineral deficiency. Uptake of all the elements studied were most severely affected by deficiency of nitrogen; the effect of phosphorus deficiency was least. Potassium deficiency reduced Na and Ca uptake by 50% and 30%, respectively. In maize also, potassium deficiency reduced Ca-uptake (Singh, 1970) but in sugar beet it increases Na concentration soon after cut of (Terry and Ulrich, 1970). Similar results were also observed in rice (Das and Sen, 1980) and wheat (Das, 1974). Deficiency conditions also exercised pronounced influence on the distribution of ion taken up between shoot and root tissues and certain types of deficiency completely altered the pattern as in the case of distribution of sulpahte, Na and Mn by nitrogen deficiency and of potassium by all the three deficiency conditions. Different regions of a plant vary in their capacity for absorption and transport of ions and this difference plays an important role in determining the distribution of ions between the various parts of a plant (Higinbotham et αl., 1962; Scott and Martin, 1962). As in the case of pea (Biswas and Sen, 1959), the ions taken up first move to the top most part of the plant where the youngest leaves and buds are situated and then
Effects of nutritional deficiency 257 move downwards. When the apices and buds are transformed into flower, there is an accumulation of nutrients in the flowers and fruits and in the leaves which subtend them, irrespective of deficiency condition. Acknowledgement Grateful acknowledgement is made to the Department of Atomic Energy, Government of India for financial support. References Atkinson, G. and Davison, A. W. (1972) New Phytol., 71, 317. Biswas, B. B. and Sen, S. P. (1959) Indian J. Plant Physiol., 2, 1. Das, B. K. (1974) Studies on the Relationship between Mineral Deficiency and Metabolic Process in Plant tissues, Ph.D. Thesis, Kalyani University, Kalyani. Das, B. K. and Sen, S. P. (1974) Effect of mineral deficiency on photosynthetic CO 2 fixation by crop plants: in Symposium on Radiations and Radioisotopes in Soil Studies and Plant Nutrition, Bangalore, Dept. of Atomic Energy, Govt. of India, p. 207. Das, B. K. and Sen, S. P. (1980) Indian Agriculturist, 24, 61. plants: in Symposium on Radiations and Radiosotopes in Soil Studies and Plant Nutrition, Bangalore, Dept. of Atomic Energy, Govt. of India, p. 207. Das, B. K. and Sen, S. P. (1980) Indian Agricultrist, 24, 61. Graham, R. d. and Ulrich, A. (1972) PlantPhysiol., 49, 105. Higinbotham, N., Pratt, M. J. and Foster, R. J. (1962) PlantPhysiol., 37, 203. Salisbury, F. B. and Ross, C. (1974) Plant Physiology (New Delhi: Prentice Hall India). Scott, S. I. H. and Martin, D. W. (1962) Aust. J. Biol. Sci., 15, 83. Shivraj, Α. (1978) An Introduction to Physiology of Field Crops; (New Delhi: Oxford and IBH Publish ing Co.). Singh, B. B. (1970) Indian J. Plant Physiol., 13, 312. Terry, N. and Ulrich, A. (1973) Plant Physiol., 51, 783.