Effect of potassium deficiency on growth and metabolism of peanut (AraeMs hypogaea L.) plants

Transcription

1 Prec. Indian Aead. SCI. (Plant Sci.), Vol. 89, Number 5, ctober 198, pp Printed in India. Effect of potassium deficiency on growth and metabolism of peanut (AraeMs hypogaea L.) plants S K MAHABB BASHA and G RAJESWARA RA Department of Botany, Sri Venkamswara University, Tirupati , India MS received 1 September 1979 ; revised 26 June 198 Abstract. Potassium deficiency effects on growth, nitrogen and carbohydrate fractions and minerals were studied in 3 day-old peanut plants. Reduced stem length, tap root length and reduced number of leaves and primary laterals were noticed in K deficient plants. In addition, decreased levels of total protein and soluble nitrogen fractions were observed. However, high amounts of starch and total sugars were found in all the three component parts of the plant under K + deficiency. K+ deficiency also decreased the levels of potassium and calcium but increased the level of total phosphorus in peanut plants. The relevance of these changes has been discussed. Keywords. hypogaea. K + deficiency ; peanut ; metabolism ; potassium deficiency ; Arachia L Introduction Notwithstanding the fact that many studies have been devoted to the role played by potassium in plant cell, its function has not yet been exactly established. But there is considerable evidence for alteration of metabolism under K + deficiency. Essentiality of potassium in plant metabolism has been studied by many workers (Webster and Vamer 1954; Nitsos and Evans 1969, etc.). K + deficiency reduced the growth rate and cellular total nitrogen (Mccarthy and Patterson 1974). In the present study an attempt has been made to study K + deficiency effects on growth and metabolism of 3-day old peanut plants. 2. Materials and methods Peanut (Arachis hypogaea L. var. TMV-2) seeds were surface storilisod in.1~o HgC12 for 2 to 3 min, washed repeatedly and sown in porcelain pots containing acid washed sand. The plants were grown in natural photoperiods. Moisture content of the sand was maintained around 8% of the field capacity. Ten days after sowing plants were thinned to two per pot. The cotyledonary leaves were excised carefully. The pots were divided into two groups. ne group received 415

2 416 S K Mahaboob Basha and G Rajeswara Rao the complete nutrient solution of Hoagland and Arnon (195) which served as control, while the other group received K + deficient nutrient solution where KN3 and KI-I~P~ are replaced by cquimolar concentrations of their sodium salts. All the plants received respective nutrient solutions once in three days. At harvest (3 days after planting) the plants were carefully removed from the pots and the roots washed in deionised water. Growth parameters such as length of stem and tap root, number of leaves, and primary laterals and fresh weight and dry weights of stem, leaf and roots were determined. Total nitrogen (Markham 1962), protein nitrogen and soluble nitrogen (Thiman and Lees 1957); Starch (McCready et al 195) ; total sugars (I-[ighkin and Frankel 1962 ; Snell and Snell 1957) were estimated according to the standard procedures. Total phosphorus were estimated according to Bartlett (1959). Minerals (Na, K, and Ca) were estimated by flame photometer (AAC 196). All these estimations were made using dry powders. 3. Results 3.1. Growth Potassium deficiency caused significant reduction in the rate of plant growth (table 1). This was found in terms of reduced height of the plant, number of leaves, length of tap root and number of primary lateral roots. Also fresh weight and dry weight of foliage showed a decrease over control plants. Though the stem and root system exhibited an increase in fresh weight, their dry weights were lower in the potassium deficient plants Nitrogen fractions Both in control and potassium deficient plants concentration of total nitrogen, protein nitrogen and soluble nitrogen showed the same pattern of distribution in all the parts (table 2). In potassium deficient plants all the nitrogen fractions were reduced in almost all the component parts except in roots. In roots of K + deficient plants total nitrogen was not much reduced and soluble nitrogen was present in greater amounts than in the control plant roots Carbohydrate fractions Although the stems of potassium deficient plants exhibited a slight reduction in starch over control plants, the remaining parts exhibited a considerable increase in starch and total sugar concentration, thus showing an accumulation of carbohydrates in K + deficient plants (table 3) Minerals Total phosphorus and sodium concentration increased, the latter being hyperbolically accumulated in roots of treated plants. Potassium concentration showed a natural reduction (table 4). Calcium concentration too was affected as exhibited by its decrease in K + deficient plants,

3 Potassium deficiency in peanut 417 tt% ",,D t'~ ~1 "~ t"qr t"~ o or,..:. r,r "o " C r t~ e~ z o Z o Z r~,.~ tl ;>~ C "z3 + ~z z I1,,i r t"4" ed r r,g] r~

4 418 S1 K Mahaboob Basha and G Rajeswara Rao Table 3. Effect of K + deficiency on the levels of carbohydrate fractions in peanut (mg/g dry weight). Treatment Starch Total sugars Stem Leaf Root Stem Leaf Root C S.E. (4-).62 "35.6 " K " 9 S.E. (4-).22 " "38 (Moan of three replications). 4. Discussion In peanut plants K+ deficiency caused marked changes, such as reduced stem length, bushy appearance, and browning of leaf tissue. Despite the fact that fresh weight of stem and root was higher in K + deficient plants than in K + su~cient plants, suggesting high water content in stems in the absence of potassium, their decreased dry weights may be due to the altered metabolism resulting in reduction in production of photosynthetic products. ur results agree with those of Falade (1978) who found in cashew seedlings that both deficiency and excess of K + depressed the rate of growth and dry matter accumulation. Besford (1975) using tomato plants and earlier Hsiao et al (197) using maize found that mild potassium deficient plants accumulated protein and that a reduction in growth could not be attributed to a block in protein synthesis. Black (1973) stated that K + deficiency leads to accumulation of soluble nitrogen. But in the present study all the nitrogen fractions decreased under K + deficiency, except in roots, where soluble nitrogen showed a slight increase. ur results agree with those of Singh (197) who showed that K + deficiency leads to decrease in nitrogen content in maize. In considering an answer for why plants require large amounts of K + than required, Nightingale (1942) proposed that K + may be required for N + absorption over and above the amount required for other functions that K + performs. This may form the possible explanation for the reduced amounts of nitrogen fractions in K + deficient peanut plants. The accumulation of carbohydrates in leaves is explained in terms of the retardation of translooation of carbohydrates. Accumulation of carbohydrates in stem and roots in peanut plants is in agreement with the results of Protsov and Petrova (196). This contradicts the view that potassium deficiency inhibits the translocation of carbohydrates from the leaves. In K + deficient plants carbohydrate and sugar utilisation might be impaired as a result of loss of activity of one or more of the several enzymes known to require potassium. It is generally observed that many plants accumulate Na + in their roots (Collandor 1941). The higher amounts of sodium in.the roots and lesser in stem indicate that though sodium is absorbed by roots little is translocated to the tops

5 Potassium deficiency in peanut 419 ec~ e~t k t",.. ~ o P. 6 ell ~--, gg r~ do~ ~m6 I t ~ Q 9 v~ ~ I--r 9 ~ v,..* ~ + ~d ~? '~?. ~ A.o P.(B)--1

6 42 S K Mahaboob Basha and G Rajeswara Rao and suggest that K + is mobile and Na + is immobile in plants. The ability of roots to retain large amounts of sodium depends on an adequate supply of K + (Besford 1978). In peanut plants under potassium starvation compensatory amounts of sodium and phosphorus accumulated but calcium decreased in concentration probably due to its indirect effect on the uptake of ions through its vital role in metabolic pathways. Thus the results of the present study showed K + deficiency affected growth, altered nitrogen and carbohydrate contents in peanut plants. Acknowledgement The authors are thankful to Prof. M V Nayudu for providing facilities. Referenees A A C 196 ffice and tentative methods of analysis, 9th edition, Washington D.C., USA Bartlett G R 1959 Phosphorus essay in column chromatography; J. Biol. Chem Besford R T 1975 Effects of potassium nutrition on leaf protein concentrations and growth of young tomato plants ; Plant Soil Besford R T 1978 Effect of replacing nutrient potassium by sodium on uptake and distribution of sodium in tomato plants ; Plant Soil Black C A 1973 Soil plant relationships (New Delhi : Wiley Eastern) Collander R 1941 Selective absorption of cations by higher plants ; Plant Physiol Falade F J 1978 Effect of macronutrients on the growth and dry matter accumulation of cashew (Anacardium occidentale L.) ; Turrialba Highkin H R and Frankel F 1962 Studies on growth and metabolism of barley mutant lacking chlorophyll b ; Plant Physiol Hoagland D R and Arnon D I 195 Water and sand culture methods for growing plants without soil ; Circular 347, Calif. Agric. Exp. Stn. Hsiao Theodore C, Hageman R H and Tyner E H 197 Effect of potassium nutrition on protein and total free amino acids in Zea mays ; Crop Science Markham R 1962 A steam distillation apparatus suitable for microkjeldal analysis ; Biochem. J MacCarthy J J and Patterson G W 1974 Effect of cation levels of the nutrient medium on the biochemistry of chlorella. I concentration series ; Plant Physiol McCready R M, Guggate J, Sivira V and wnes H 195 Determination of starch amylase in vegetables ; application to peas ; Anal Chem Nightingale G T 1942 Potassium and phosphate nutrition of pineapple in relation to nitrate and carbohydrate reserves ; Bet. Gaz Nitsos 1t E and Evans H J 1968 The effect oi univalent cations on partic~lato starch s~nthetase ; Abstr. Am. Soc. Plant Physiol. Western Section. Program of Meetings, Utah State University, Logan, Utah, June Protosov P V and Petrova 196 The cotton plant (in Russian) 4 Izd. Vo. AN Uz. SSK p. 396 Singh B B 197 Effect of potassium deficiency on growth, yield and mineral content of maize ; Indian Y. Plant Physiol Snell F D and Snell C T 1957 Colorimetric methods of analysis (New York : Van-Nostrand D) 3 23 Thiman K V and Lees G M 1957 Protein synthesis during water uptake by tuber tissue ; Plant PhysioL Webster G C and Varner J E 1954 Peptide bond synthesis in higher plants. II Studios on the mechanism of synthesis of 7-glutamyl cysteine ; Arch. Biochem. Biophys