INFLUENCE OF DIFFERENT LEVELS OF SOIL MOISTURE STRESS ON PHYSIOLOGICAL PARAMETERS OF UPLAND RICE CULTIVARS

Indian J. Planl Physiol., Vol. XXXIV, No.4, pp. 387-39J (Dec., 1991)

SHORT COMMUNICATION

INFLUENCE OF DIFFERENT LEVELS OF SOIL MOISTURE STRESS ON PHYSIOLOGICAL PARAMETERS OF UPLAND RICE CULTIVARS '.i

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G. RAMA KRISHNAVYA AND K.S. MURTY

Division of Physiology, Central Rice Research Institute, Cuttack -753006

Received on 3 April, 1991

Five upland rice varieties were subjected to soil moisture stress of 25% field capacity at seedling stage. With increase in soil moisture stress, there was decrease in relative water content and water potential ofleaf. The cultivar which maintained high relative water content and positive turgor inspite of reduced leaf water potential during stress also had optimum photosynthesis 8Bd' solute accumulation as evident from osmotic potential.

Drought resistance is the result of numerous morphological, anatomical and physiological characters, both constitutive and inducible, wbich interact with the maintenance of growth and developmental processes under edaphic and climatic con­

ditions (Steponkus et al .• 19S0). Recently there has been considerable emphasis on

osm(\tic adjustment as an adaptive response to waler stress by higber plants (Hsiao

et al., 1916, Turner, 1979). According to Steponkus et al. (1982) and Rana Munns

(1990) the osmotic adjustment is an increase in the concentration of cell solutes per­ mitting a positive turgor potential to be maintained at lower values of water potential

than would be possible, if the solute concentrations were to increase solely due to tissue water loss. Compared to other cereals, little information is available on the

response of rice to water deficit. Present investigation examined certain possible

physiological differences in rke cultivars under drought conditions.

Seeds of each of the five upland rice cultivars, CR 143-2-2 (Bala X Lalnakanda 41), Annada, Kiran, Annapurna and Dhangora were sown in 20 porcelain pots in a

complete randomised block design during dry season (January-April, 1987). Each pot

contained 7 kg of wen pulvarised soil. At 3 week stage, the plants were subjected to

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w 00 00 Table I. Effect of soil moisture stress on RWe. LWP and LDR of five upland rice cultivars

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Adequate amount of water was replenished daily to maintain the desired levels of stress as described by Matsushima (1962). Fifteen days after initiation of stress, observations were made in triplicate on fully expanded 2nd leaf from top. Relative

water content (Slatyer and Barrs, 1965), leaf water potential (Scholander et aI., 1964)

and leaf adaxial diffusive resistance (Saini and Rathore, 1984) were estimated. Osmotic potential (Janardhan et al., 1975) was recorded from 5th day of initiation of stress at 3 days interval

With increase in moisture stress from 21 to 35 days after sowing, there was de­ crease in relative water content (RWC) and leaf water potential (LWP) and increase

in leaf diffusive resistance (LDR) (Table J). The RWC was more or less stable even

at 25% F.C. in CR 143-2-2 inspite of considerable reduction in LWP. The LDR was high in Annapurna and low in CR 143-2-2 at 25% F.C. Thus the culture CR

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Fig. 1. Effect of soil moisture stress (50% F.C. from 21 to 35 days after sowing) onrelatioDship betwden leaf water potential and osmotic potential. Vertical bars indicate stanqard deviation of mean of three determinations.

G. kAMAKtUSHNAYYA AND K.S. Mutt-rV

143-2-2 maintained relatively high RWC inspite of reduced LWP with near normal

LOR.

Futher the induced soil moisture stress (50% F.C. from 21-35 days after sowing) resulted in a drop in osmotic potential (OP) along with L WP in the four

cultures tested (Fig. 1). Eight days after initiation of stress, the OP of CR 143-2-2

dropped below to the corresponding LWP and continued to decline till 14th days of stress. On that day the OP value was lower by about 0.62 MPa to LWP which might have resulted in positive turgor. Such phenomenon was not clear in other cuItivars.

Cutler et al. (1980) and Steponkus et al. (1982) working with rice observed that

under slow drying conditions, despite reduction of leaf water potential, bulk leaf turgor remains unchanged as a result of osmotic adjustment. Rana Munns (1990) observed that osmotic adjustment might be an adaptive mechanism for surviving stress rather than for growth during stress. Morgan (1977) advocated the possibility of improving the drought resistance of crop species on the basis of differences in osmotic adjustment.

In the present investigation CR 143-2-2 showed (i) lowered osmotic potential and maintained higher relative water content (+ve turgor) inspite of lowered water potential and (ij) low diffusive resistance. These two characters might have helped

in better conductance of CO2 through stomata even during stress, for optimum

photosynthesis and solute accumulation leading to the possibility of osmotic adjust­ ment and consequent tolerance to soil moisture stress conditions. Drought tolerance in term of yield under moisture stress by CR 143-2-2 has been amply demonstrated by Rama Krishnayya and Murty, (1991).

REFERENCES

Cutler, J.M., Shahan, K.W. and Steponkus, P.L. (1980). Dynamics of osmotic adjustment in rice.

Crop Sci., 20: 310-313.

Hsiao,

T.e.,

Janardhan, K.V., Parasiva Murty, A.S., Giriraj, K. and Panchaksharaiagh, S. (1975). A rapid method for determination of osmotic potential of plant cell sap. Curro Sci., 44:

390-391.

Matsushima. S. (1962). Some experiments of soil-water plant relationship in the cultivation of rice. Proc. Crop Sci. Soc. Japan, 31 : 115-121.

Morgan, J.M. (1977). Differences in osmoregulation between wheat genotypes. Nature, 270: 234­

235.

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l

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Rana Munns (1990). Why measure osmotic adjustment? pp. 890-898, In International Congress of PJant Physiology held at New Delhi, February, 15-20,1988.

Saini, B.C. and Rathore, T.R. (1984). Diffusive conductance of rice leaves during gradually in­ duced water stress, Ann. Appl. Bioi., 104 : 537-542.

Scbolander, P.P., Hammel, H.T. Hemmingsen, E.A. and Bradstreet, E.D. (1964). Hydrostatic pressure and osmotic potential in leaves of mangroves and some other plants. Proc. Natl. Acad. Sci. USA, 52: 199-125.

Slatyer, R.O. and Barrs, H.D. (1965). Modification of tile relative turgidity technique with notes on its significance as an index of internal water status of leaves. pp. 331·342, In Methodology of Plant Ecophysiology. Eckardt, P.E. (ed.), UNESCO, Paris.

Steponkus, P.L., Cutler, 1.M. and O'Toole, 1.C. (1980). Adaptation to water stress in rice. pp. 401-418, In Adaptation of plants to water and high temperature stress. Turner, N.C. and Krame, P.l. (eds.) Wiley Interscience, New York.

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