BIOLOGIA PLANTARUM (PRAHA)

20 (6) : 425--430, 1978

I n f l u e n c e o f M o r p h a c t i n o n P e a r l M i l l e t P l a n t s u n d e r W a t e r S t r e s s

1~. L. KACKAR, S. KATHJU and A. N. LAHIRI

Division of Soft.Water.Plant Relationship, Central Arid Zone Research Institute, Jodhpur*

Abstraet. The effects of foliar application of morphactin (0, 10, 50 and 100 ppm) on Pennisetum Syphoides (cv. HB3) have been studied under different soil moisture conditions (0.3, 3 and 9 X 105 Pa tension). Morphactin application reduced the plant height, increased the tillering and leaf number of the main shoot and adversely affected the growth characters associated with the grain production. The overall performance of plants was not improved by morphactin treatment under low moisture regime and it did not impart any efficiency of water use for grain production. Findings on the phosphorus and potassium levels of the shoot tissue suggested a possibility of its interference in the nutrient uptake process.

Morphac t in has been claimed to be a promis ing an t i t r ansp i r an t (SCHNEIDER 1970, 1972). An a t t e m p t has the re fore been made to s t u d y the influences of m o r p h a c t i n on the dif ferent pe r fo rmance pa rame te r s of pear l millet p lan ts g rown unde r different soil mois ture tensions in the con tex t of wa te r use. S t u d y also relates the influences of morphac t in on the phosphorus and po- tass ium up t a ke of p lan ts in view of the meagre in fo rma t ion on this subject .

Material and Methods

S t u d y was u n d e r t a k e n wi th pearl millet p lants ( P e n n i s e t u m typhoides cv. H B 3) grown in 9 kg of soil (containing clay : sand : f a r m y a r d m a n u r e - - 1 : 2 : 1 wi th supplements of N, P and K a t ca. 30 kg per 1 ha) in pots hav ing l ining and covers of po ly thene . The p lan ts were sp rayed wi th an aqueous solut ion of morphac t in (chlorf lurenol-methyl , E M D 7301 a t 10, 50 and 100 ppm) th ree t imes dur ing the growing per iod (i.e. 27th, 42nd and 55th d a y f rom sowing). Control p lants were sp rayed wi th disti l led water . The soil mois ture unde r different t r e a t m e n t s was ma in t a ined a t 0.3, 3 and 9 x 105 P a tensions by differential wa te r ing af te r the weighing of pots a t an in te rva l of 24 h. Ten pots , each hav ing two plants , se rved as repl icates, which were randomized . Observa t ions on the height , leaf number , t i l ler n u m b e r were recorded t h r o u g h o u t the growing per iod a t an in te rva l of 10 d. D a t a were also recorded on the d ry m a t t e r of roo t and shoot a t harves t ,

Received January 12, 1978; accepted February 27, 1978 * Address: Jodhpur -- 342 003, India.

425

426 N.L. KACKAR ET AL.

length and girth of the main shoot ear, and the grain yield. The significance of results has been adjudged by the analysis of variance wherever necessary. The phosphorus contents of shoot samples were estimated colorimetrically after colour development with stannous chloride. Potassium was estimated by a flame photometer.

Results and Diseussion

Application of morphactin at increasing concentrations progressively de- creased the plant height and the effect was highly significant (Table 1). The moisture level also had a significant effect and the decrease in height was greater between 0.3 and 3 • 105 Pa than that between 3 and 9 • 105 Pa. The interaction between soil moisture and morphactin concentration was significant at 5% level. The inhibitions of growth at higher concentration of morphactin (50 and 100 ppm) were less under low moisture regime. The leaf number of the main shoot was significantly reduced under low soil moisture conditions. It was increased by morphactin application only at 10 ppm concentration. Morphactin has been reported to inhibit the elongation of the stem in a number of plants through retardation of the internode elongation (ScHNF, IDER 1972). In the present study inability of morphactin to reduce the leaf number suggests that it did not influence the number of leaf primordia, although the height of plant as such was reduced. In di- cotyledonous plants with compound leaves there are reports of the tendency of simplification of the compound leaves and also malformations (SCHNEIDER 1970). In the present study there was no anomaly in the leaf formation and growth due to morphactin treatment.

The tiller number increased with the increasing concentrations of morph- actin while a decrease was observed with the increase in moisture tension. Although the influence of soil moisture on tiller number was not large enough to be significant, it significantly reduced the number of tiller ears. The analysis of the data on number of tiller ears did not indicate any significant effect of morphactin as tillers induced by this compound did not bear any ear. It has been mentioned that morphactin decreased the height but in- creased the tiller number. As a consequence the data on the dry matter (at harvest) indicated significant increases at 50 and 100 ppm concentrations as compared to control. The dry matter decreased with increasing soil moisture tension irrespective of the morphactin concentrations. However, the magnitude of fall in dry matter at higher soil moisture tension was smaller at higher morphactin concentration (50 and 100 ppm). S~AR~A and VATSA (1976) have also observed an increase in the tiller in pearl millet plants treated with morphactin.

The root growth in terms of dry weight at harvest indicated an increase at l0 ppm concentration but higher doses, particularly 100 ppm depressed the root growth. The root growth again decreased with the increasing moisture tension. SCHNEIDER (1970) has also reported that at lower con- centrations morphactin increases the growth of primary roots in the seedlings and that its effect on the roots is the reverse of that on shoots.

The morphactin and soil moisture deficits significantly decreased the length of the main shoot ear. At a high concentration of morphactin (100 ppm) the decrease in the main shoot ear seemed grca~er at higher soil moisture

INFLUENCE OF ~ORPHACTIN AND WATER STRESS 427

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428 N . L . K A C K A R ET AL.

tension, but the differences were not large enough to be significant. The girth of the main shoot ear significantly decreased with the increasing concentrations of morphactin and soil moisture tensions. At high concen- tration (100 ppm) morphactin severely reduced the girth of the main shoot ear in plants growing at low soil moisture (3 and 9 x 105 Pa tension).

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Fig. 1. Effect of different m o r p h a c t i n concentrat ions at different mois ture tens ions on the con- centrat ion o f phosphorus and p o t a s s i u m in the shoot: 0 -- control; [ ] morphac t in 10 ppm; �9 morphac t in 60 ppm; �9 morphac t in 100 ppm.

The grain yield per plant was significantly reduced by both morphactin and moisture stress. Thus morphactin treatments did not improve the yield under low moisture regime. The reduction in yield from the main shoot ear was significant with morphactin treatment but it was not large enough to be significant in the case of moisture stress. The moisture stress reduced the number of tiller ears thereby significantly reducing the grain yield per plant. Morphactin increased the tiller number but the tillers did not contri- bute to the yield due to the lack of ear formation.

Fig. 1 indicates that morphactin treatments generally reduced the potas- sium concentration and increased the phosphorus concentration, particularly at the later stages of growth in all three moisture regimes. The magnitudes of the increase and decrease, however, displayed certain variations. The absolute quantity of phosphorus (mg/plant) at harvest, showed an increase over the control virtually at all tensions but the potassium level apparently decreased (Table 2). The increase in potassium due to morphactin treatment

INFLUENCE OF MORPHACTIN AND WATER STRESS 429

T~L~. 2 Effect of morphactin and soil moisture tensions on the absolute quantities of P and K at final harvest

Morphactin mg P/plant at soil moisture tensions mg K/plant at soil moisture tensions [• 105Pal [X 105Pal

[ppm] 0.3 3 9 0.3 3 9

0 1.500 0.709 3.800 1300 1182 1152 10 3.968 3.269 3.941 756 680 564 50 4.815 3.144 5.478 958 891 896

100 1.125 3.880 4.419 817 987 756

as observed by ASIF and ERGENOGLU (1975) in the snapdragon could not be established in pearl millet.

The transpiration coefficient (water used in g per g dry matter or grain) in relation to dry matter production declined with the increasing soil moisture tension. The coefficient was of the order of 1017.6, 830.2 and 713.8 at 0.3, 3 and 9 • 105 Pa soil moisture tension, respectively. This increasing trend of water use efficiency with decreasing soil moisture obtains support from previous findings (VIERS 1962, PATIL and DE 1976). Morphactin slightly decreased the transpiration coefficient in relation to dry matter production (Table 3) and this could be due to marginal increase in the dry matter of the shoot caused by increased tillering (Table 1). But this index in relation to grain production increased with the increasing morphactin concentration indicating an obvious induction of inefficiency of water use. Thus the present results do not seem to confirm the earlier reports that the morphactin reduces the water requirements of plants and helps in moisture conservation (ScHzqE~- ])ER 1972).

In the light of the above it appears that the advantages of morphactin application are rather limited. Again, it seems that the influences of morph- actin on the nutrition status of plants may be as important as its proposed action on the indigenous gibberellin or gibberellinqike compounds or auxins.

TABLE 3 Effect of different concentrations of morphactin on the water use efficiency in terms of trans. piration coefficient. The plants were maintained at 0.3 X l0 s Pa tension

Morphactin Water transpired Transpiration coefficient in relation to [ppm] [g/pot/ dry mat te r grain yield

0 25 440 2035.2 3043.0 10 25 420 2041.6 3185.4 50 24 360 1831.4 6766.6

References

Asxl~, M. L., EROE~OGLLr, F.: The effect of morphactin on the nutrient concentration of snap- dragons. -- J. agr. Sci. 85 : 565--566, 1975.

PATIL, B. B., DE, R.: Influence of anti transpirants on rapeseed (Brassica campestris) plants under water-stressed and non-stressed conditions. -- Plant Physiol. 57 : 941-- 943, 1976.

4 3 0 N . L . KACKAR ET AL.

SCHNEIDER, G.: Morphactins: Physiology and performance. -- Annu. Rev. Plant Physiol. 21 : 499--536, 1970.

SCHNV.n)~.R, G.: Morphaetins and plant growth regulation. -- In: KALDEWEY, H., VXI~D~U~, Y. (ed.): Hormonal Regulation in Plant Growth and Development. Pp. 31. --331. Verlag Chemie, Weinheim 1972.

S~A~MA, Y. P., VATSA, V. K.: Effects of ehlorflurenol on the growth ( f pearl millet. -- Indiar~ J. agr. Sci. 46 : 351--354, 1976.

VXETS, F. C. Jr.: Fertilizers and efficient use of water. -- Adv. Agron. 1~ : 223--264, 1962.