Planta (Berl.) 102, 372-373 (1972) 9 by Springer-Verlag 1972

Short Communication

Synergism between Cytokinins and Nitrate in Induction of Nitrate Reductase Activity in Fenugreek Cotyledons V~D PX~XASH Division of Genetics, Indian Agricultural Research Institute, ~Iew Delhi, India Received October 29, 1971 Recently Rijven and Ved Parkash observed that fenugreek (Trigonella [oenum graecum L.) cotyledons respond readily to cytokinins with increased expansion. This growth stimulation is enhanced by the presence of an exogenous nitrogen source. Since cotyledons store reserve proteins this finding was unexpected. The present communication reports the effects of cytokinins, light, and nitrate ions on nitrate reduetase activity in these cotyledons. Cotyledons, average weight 7.Smg after soaking, were separated from the embryonic axis b y a cut through the dry seed; the space between these is indicated by a groove in the seed exterior. Sterilization, transfer of cotyledons to test solutions, and other manipulations were performed as described by Rijven and Ved Parkash. Nitrate reductase activity was studied in extracts as follows: lots of 10 cotyledons (two replicates per treatment) were ground in a mortar with 4 ml 0.1 M p H 7.5 phosphate buffer containing 5 mM cysteine, and were then eentrifugated for 10 minutes at 5000 g. Supernatant, 0.1 or 0.2 ml, was assayed (Spencer, 1958), with D P N H generated b y alcohol dehydrogenasc. The final volume was 0.5 ml. After 30 min at 30~ the reaction was stopped b y adding 0.5 ml of sulfanilamide and hi- (1-naphthyl)-ethylenediamine dihydroehloride. After color development for 15 rain and centrifugation for 15 rain at 4000 g, the absorbaney (A) was read at 540 nm. Results are expressed as A540 per 0.5 cotyledon per 30 min. One unit of A540 corresponds to 30 nmoles of nitrite produced. Nitrate reductase activity could not be demonstrated in cotyledons incubated in water or in 20 mM nitrate in darkness (Table 1) but could be shown when, in addition to nitrate, either cytokinins (zeatin, benzyl

Cytokinin-~itrate Synergism

373

Table 1. E/]ect o/cytokinins and light on nitrate reductase activity ol cotyledons after

incubation /or 24 h with or without 20 m M nitrate, light and cytokinins. For determination o/nitrate reduction activity see "Materials and Methods" Fresh weight increases (%)

Nitrate reductase (A540)

• 10 -5 M • 10-5 l/i • 10-5 M • 10-5 M X 10 -5 M • 10-5 M

7.3 10.2 21.4 25.6 24.3 28.2 34.6 32.6

0.00 0.01 0.00 0.00 0.00 0.123 0.136 0.120

5 x 10-~ M 5 X 10-~ l~I 5 • 10-5 M 5 • 10-21V[ 5 • 10 -~ M 5 • 10-5 M

11.2 13.6 34.2 38.6 32.3 48.7 55.6 49.2

0.00 0.065 0.000 0.000 0.000 0.58 0.69 0.63

Dark H20 KN0 a Kinetin Zeatin ]3A Kinetin + KNO~ Zeatin ~- KNO~ BA + K-NO3

5 5 5 5 5 5

Light H20 ICNO~ Kinetin Zeatin BA Kinetin -]- KNO 3 Zeatin + KNO 3 BA + KNO a

a d e n i n e , k i n e t i n ) or l i g h t was p r e s e n t . M t e r 24 h i n t h e p r e s e n c e of b o t h e y t o k i n i n s a n d l i g h t , t h e a c t i v i t y w a s y e t higher. T h e l a c k of r e s p o n s e t o 20 m ~ n i t r a t e i n t h e a b s e n c e of e y t o k i n i n s s u g g e s t s t h a t c y t o k i n i n s a r e r e q u i r e d for p r o t e i n s y n t h e s i s . The author is grateful to Dr. H. K. Jain, Head of the Division of Genetics, Indian Agricultural Research Institute, New Delhi, for kind provision of facilities.

References

Rijven, A. H. G. C., Parkash, V. : Cytokinin-induced growth responses by fenugreek cotyledons. Plant Physiol. 45, 14-18 (1970). Spencer, D. : A D P N H specific nitrate reduction from germinating wheat. Aust. J. biol. Sci. 12, 181-191 (1959). Ved Parkash Division of Genetics Indian Agricultural Research Institute New Delhi-12, India 26 Planta (Berl.), Bd. 102

Synergism between cytokinins and nitrate in induction of nitrate reductase activity in fenugreek cotyledons.

Synergism between cytokinins and nitrate in induction of nitrate reductase activity in fenugreek cotyledons. - PDF Download Free
91KB Sizes 2 Downloads 0 Views