PHOTOPERIODISM IN RICE

Transcription

1 PHOTOPERIODISM IN RICE II. PHOTOPERIODIC RESPONSE OF FOUR EARLY VARIETIES OF RICE OF UTTAR PRADESH BY GADADHAR MISRA Department of Botany, Ravenshaw College, Cuttack 3, India {Received 20 September 1953) (With 2 figures in the text) INTRODUCTION Sircar (1939) and Sen (1940) are the pioneer workers in India to discuss the scope of vernalization and photoperiodism in Indian agriculture. Its practical utility for rice is threefold (Sircar, 1946). First, the particular variety could be grown in a much shorter time; secondly, by inducing early maturity, it could escape floods and other adverse conditions; and thirdly, early harvesting would leave sufficient time for the preparation of fields for the crops following in rotation. Considering this, it is surprising that sufficient work to explore the possibilities of applying this technique to rice has not yet been done. In India the photoperiodic work on rice is confined mostly to two States Bihar and Bengal. Alam (1940-1) and Saran (1945), working with several varieties of Bihar rice, came to the conclusion that, excepting the ' Sathi' variety, by the application of short days, any other variety of paddy, irrespective of the class or maturity period to which it belonged, could be induced to flower within days of germination. The 'Sathi' variety which normally flowers in 60 days, did not respond to this treatment at all. Saran (1950) noted, with a late 'Aman' paddy of Bihar, that the minimum eflective period of short days to bring about early flowering is 15 days. Sircar (1942, 1946), using a winter paddy variety ' Bhasamanik', and Sircar & Parija (1949), with two other winter rices of Bengal, 'Rupsail' and 'Patnai', noted considerable earliness by application of short days to seed-beds for varying periods and also when prolonged till ear emergence. The results with summer varieties seem to bediflerent. Sircar & Ghosh (1947) observed in two 'Aus' varieties of Bengal rice, 'Charnock' and 'Panbira', that short days delay flowering by 7-12 days and annul the eflect of vernalization by high temperature. Kar (1946), however, observed an earliness in ear emergence in two 'Aus' varieties of Bengal rice, ' Dharial' and ' Kataktara', by application of both short and long days. Since the photoperiodic behaviour of rice varies with varieties it is desirable to note accurately the response to daylength of the diflerent varieties of the other rice-growing States of India in order that all the benefits that accrue from a study of photoperiodism can be utilized to the fullest degree. With that end in view the photoperiodic response of eighteen varieties of rice, twelve from U.P. and six from Orissa, have been investigated. The present communication embodies the results of the investigation into the photoperiodic response of some early varieties (Mitra & Gupta, 1945) of rice of U.P. A preliminary brief report was published earlier (Misra, 1951).

2 30 GADADHAR MISRA MATERIAL AND METHOD Pure seeds of the four early varieties T. 136, (Rajbhog), (Banki) and Ch. 10 (Tandwa White), procured from the Nagina Rice Research Station, U.P., were used in this experiment. The grains after preliminary selection for uniformity of size and colour by eye were sterilized in 0-2% formahn solution for 3 hr., after which they were thoroughly washed in tap water. They were then sown in earthenware pots (11 x 10 in.). The soil consisted in each case a fresh mixture of well pulverized garden loamy soil and cowdung manure in the proportion of 8: i by volume. Short-day treatment consisted of a daily 10 hr. exposure to natural daylight from 8.00 a.m. to 6.00 p.m. For the rest of the 24 hr. cycle, i.e. from 6.00 p.m. to 8.00 a.m. next morning the pots were removed to a well-ventilated dark room. Long-day treatment consisted of a 24 hr. continuous illumination obtained by supplementing the natural day length with artificial illumination from a 1000 W. gas-filled 'Osram' bulb hung at a height of 5 ft. from the soil surface. After the termination of the photoperiodic treatments the treated pots were kept outside in the pot culture enclosure in the Botanical gardens along with the respective control sets and received the normal daylength and the natural environmental conditions till the time of harvesting. Care was exercised in maintaining uniform soil moisture throughout by frequent applications of water. All other conditions except light were kept as far as practicable identical in all treatments. This experiment comprised two series. In the short-day series, 10 hr. short day was given to i8-day-old seedlings for 30 days in one set, and prolonged till ear emergence in another. In the long-day series, 24 hr. continuous illumination was given to i8-day-old seedlings for 20 days in one set and for 30 days in another. SHORT-DAY SERIES Time of heading The criterion of ear emergence was taken as the exsertion of the inflorescence through the last leaf (flag leaf) sheath of the main shoot. Observations were taken each day at about 3-00 p.m. Data for ear emergence are graphically presented in Fig. i. It is seen that there has been a considerable delay in the ear emergence in both the sets receiving shortday treatments, the average delay being 6-93 days in plants treated for 30 days and in those treated for 90 days. From the statistical analysis of the data it is seen that the difference between the two short-day treatment sets is also significant, the prolonged short-day treatment producing a longer delay than the other. The treatment effects do not seem to vary with the varieties as indicated by the non-significance of the variety x treatment interaction. In addition to the delaying effect of the short days on the emergence of the ears, a peculiar behaviour was noted in the case of the experimental sets where short-day treatment was given till the ear emergence. In these cases the emergence of the ears on the main shoot was totally suppressed in a number of plants. This behaviour was noticed in all the four varieties. The suppression was as high as 50% in the two varieties T. 136 and, dropping down to 41-6% in variety ^^^ to a still smaller value of 21 % in variety Ch. 10. On dissection of the culms in these cases it was observed that although the ears were formed their growth was arrested inside the boot. Thus the effect of the prolonged short-day treatment may be resolved into two groups (i) delay in the

3 Photoperiodism in rice 31 ear emergence of the main shoot (ii) suppression of the ear emergence due to the failure of stem elongation. 104 T.N. 27 Ch r I ABC ABC ABC ABC Fig. I. Time from sowing to ear emergence of the main shoot in days in the four varieties of early (summer) rice, T. 136,, T.N. 27 and Ch. 10. A, control received full length of day at Allahabad; B, io hr. short days given to i8-day-old seedlings for i month; C, io hr. short days given to i8-day-old seedlings till ear emergence. Tillering Tiller counts were made at fortnightly intervals. It was observed that short days profoundly influenced the production of tillers. Where short days were given for only 30 days the tillers were much less than in the controls in the first count in each variety. But after the expiry of the treatment period when the plants were transferred to control conditions tiller production speeded up and attained the level reached by the control plants. The interesting fact was that where the short days had been continued till ear emergence tiller production had been kept at a very low level in comparison with the controls throughout the life period of the plant. Height The heights of the plants were recorded at regular intervals along with the count of tillers. Short-day treatment for 30 days showed no difference from the controls at any stage. Continued short-day treatment, on the other hand, brought about a decrease in height at the later stages, while in the preliminary stages there was no marked difference from the controls. In the last count the differences between the treated sets and the controls were conspicuous. Grain yield After about 5 weeks from the time of ear emergence, when the grains matured fully, all the ear heads formed in each plant were collected separately. The grain weight per plant was recorded after drying the ears in the sun for i week. The data are presented graphically in Fig. 2. It may be seen from Fig. 2 that the plants treated for 30 days show

4 \ ' ' 32 GADADHAR MiSRA an increase of grain yield per plant in all the four varieties. The overall effect of the 30-day short-day treatment in all the varieties is an increase of i6-6% in grain weight per plant over the controls. The effect of the prolonged short-day treatment is adverse on the grain yield in all the varieties, and it is highly significant at i % level, the mean decrease in grain yield in all the varieties being 62-0% in comparison with the controls. 6 5 c 4 ' pla lu Q- D U ^ i T. 36 T.N. 22 T.N. 27 Ch.10 \ '; s \ \ \\ n 1 1 ; \ \ \ zzz \ \ \ \p^ " \.. \ \ \ ' ABC ABC ABC ABC Fig. 2. Grain yield per plant in grams in the four varieties of early (summer) rice, T. 136, T.N. 22, T.N. 27 and Ch. 10. A, control received full length of day at Allahabad; B, 10 hr. short days given to i8-dayold seedlings for i month; C, 10 hr. short days given to i8-day-old seedlings till ear emergence. Components of yield The data for the components of yield, such as number of panicles per plant, length of panicle, number of spikelets per panicle, number of grains per panicle, percentage of grains set per panicle and weight of 1000 grains is given in Table i with their standard error mean and critical difference. A study of Table r shows that there has been an increase in the number of panicles in all the varieties by short-day treatment for 30 days, but the increases in varieties T. 136 and T.N. 27 are comparatively more than those in varieties T.N. 22 and Ch. 10. In the prolonged treatment set, however, the number of panicles has been considerably decreased in all the varieties. It is interesting to note that the plants under normal conditions, as well as those in the 30-day treated set, produced tillers all of which do not survive up to maturity; later formed ones die away without forming ears. The results with prolonged short-day treated plants show that in the four varieties almost all the tillers live up to maturity and bear ears. Thus prolonged short-day treatment, though producing comparatively few number of tillers, helps all of them to survive, and thereby the ratio of the tillers surviving and forming ears to the total number of tillers formed is higher than in the controls and the 30-day treated set. The average length of the panicle for the different treatments is slightly increased in all the four varieties by short-day exposure for a month. When short-day treatment is prolonged until heading the length of the panicle decreases in all the varieties, the average length being cm. in the prolonged short-day set as against cm. in the controls.

5 T^rf 3tm en t varieties T. 136 Ch. 10 Ch. 10 Ch. 10 Ch.io Ch. 10 Photoperiodism in rice Table i. Components of yield Figures in brackets indicate percentage increase ( +) or decrease ( ) from control. Control S Short day for 30 days '55 ( + 8-6) Short day till ear emergence No. of panicles per plant Length ( + 6-5) (-30-9) the panicle in cm (-17-5) No. of spikelets per panicle (33-2) ( + 4-7) No. of grains per panicle ( + 3-5) Percentage of (-1-1) (-38-6) grains set per panicle (-22-2) s.e. and CD. at 5 % of treatment mean 0-06 o-i s.e. and CD. at 5 % for comparing two individual means I Ch.io Weight of 1000 grains in g (+1-5) (-13-0) The number of spikelets per panicle does not show an uniform behaviour in all the varieties in the 30-day treated set. In variety T. 136 alone the value is higher in the controls than in the treated set, but in the other three varieties the value is higher in the treated set than in the controls. The overall effect on all the varieties is an increase of 4-6 % over the controls. In the prolonged treatment set a significant decrease is observed in all the four varieties than in the controls, the mean value averaged over all the varieties showing a decrease by 66-0 % from the controls. o New Phyt. 54, i

6 34 GADADHAR MisRA The number of grains per panicle has been influenced in a similar manner as the number of spikelets. Excepting variety T. 136, the treated ones of other varieties of the 30-day treated set indicate an increase in the number of grains per ear over the controls. The behaviour of variety T. 136 in this connexion is different in the sense that the control plants have a larger number of grains per ear than the treated ones, but in no way the weight of grains obtained from the controls is higher than those obtained from the treated ones. Greater number of ear heads is responsible for the increased weight of grams. The percentage of grain setting has been slightly decreased in the 30-day treated set^ whereas the prolonged treatment set shows a very considerable decrease, which is due to the formation of a large number of empty spikelets in them. The 1000 grain weight has not been generally affected by the short days for 30 days while prolonged short days have decreased the same by 13-0%. LONG-DAY SERIES The data presented here pertain to the plants which were given long-day exposure of light and they are on the same aspects to which attention was given in the short-day series. Time of heading The time of ear emergence for the various sets of plants receiving long-day treatments are presented in Table 2 and its analysis of variance in Table 3. It is seen that long-day treatment for 30 days has delayed the ear emergence of the main shoot and the delay is statistically significant. Table 2. Time from sowing to ear emergence of the main shoot + indicates earliness; indicates delaying effect. Sowing date 7 May Treatment commenced 25 May Treatments Control L. day for 20 days L. day for 30 days s.e. mean CD. at 5 % Average no. of days from sowing to ear emergence T.N Difference from control in days T.N Table 3. Analysis of variance {time of ear emergence) Source of variation D.F. s.s. M.S. F 5%F I%F Varieties {V) Treatments (T) Interaction (Fx T) Error Total I ** Significant at i % level.

7 Photoperiodism in rice 35 Tillering and height of plants From a record of the tillers and height of the plants at the final stage it was clear that long-day treatment for 20 days had a stimulating effect on the vegetative grovrth of the plants. There was a significant increase in the number of tillers in comparison with the controls. The height of the plants was also greater under this treatment. But when the period of long-day treatment was increased to 30 days there did not appear to be any significant difference from the controls in any of these characters. Grain yield After drying the grains by the usual method their weight was recorded and the data are presented in Table 4 with the statistical analysis of the data in Table 5. Table 4. Average yield of grains per plant in grams Figures in brackets indicate percentage increase (+) or decrease ( ) from controls. Treatments Control L. day for 20 days L. day for 30 days s.e. mean CD. at 5 % ( + 8-7) 5-73 ( ) Source of variation Varieties (F) Treatments {T) Interaction (Vy.T) Error Total Table 5. Analysis of variance {grain yield) On per pot basis, i.e. total of four plants. D.F. I s.s M.S F %F i%r Though there seems to have been a slight increase in grain yield in both the varieties under long-day treatments, it is not statistically significant. Components of yield A perusal of the data concerning the components of yield led to the following conclusions: (1) Number of panicles had been slightly increased under the long-day t^^^tments for both the durations and this increase was statistically significant. (2) There did not appear any conclusive difference as to the length of the panicle in the treated and control plants. (3) Long-day treatments had no infiuence on the number of spikelets produced per panicle. (4) Number of grains in the set receiving long days for 30 days showed a marked increase which was statistically significant. (5) Appreciable result was seen as to the percentage of grains set per panicle. (6) The average weight of 1000 grains had not been altered at all by the long-day treatment. 3-2

8 36 GADADHAR MISRA DISCUSSION It is clear from the effect of 10 hr. short days on these early varieties that short-day treatment not only produces a significant delaying effect in the time of emergence of the ears of the main shoot but to a great extent inhibits their emergence. Further, in a certain percentage of the total population it was seen that the ears of the main axis did not emerge out of the boots but remained arrested inside and ultimately died within the leaf sheaths. On dissection of the culms in these cases it was noticed that the vegetative apices have all changed to panicles but they have been arrested inside the flag leaf presumably because of the failure of the axis to elongate. Detailed histological and micro-chemical tests of the culms below the arrested spikelets might throw more light as to the cause of the inhibition of stem elongation. Arrest of ears of a similar nature inside the flag leaf was observed by Purvis (1934) in Petkus winter rye. She observed that the death of the ears inside the leaf sheaths under continued short days was associated with failure on the part of the stem to elongate. She obtained evidence that normal development of the vascular supply also failed. She also observed phloem necrosis and this, according to her, might be the proximal cause of the failure of elongation and emergence of the ear. As Wanser (1922) has said, the stem has apparently specific photoperiodic requirements for stem elongation in the absence of which such failure in elongation probably takes place. As to those plants where suppression of ear emergence was not noticed it may be said that they might not have reached the same developmental stage as the others to react to the photoperiodic perception. Further work is necessary before such a conclusion can be drawn. Results similar in trend to that of these four varieties of early rice were obtained by Sircar & Ghosh (1947) in Charnock and Panbira, two early (summer) varieties of rice of the State of Bengal. Sircar & Parija (1949), however, could not get any delaying effect in Jhanji 34 and Bhutmari 36, two other Bengal summer varieties by giving similar treatments. Kar (1946) by giving long and short days separately for 15 days to two early (summer) and eight late (winter) varieties of Bengal rice, made a general statement that in different varieties of paddy high temperatures associated with short daylengths were conducive to earliness, and low temperatures or longer daylengths produced retardation. In these four early varieties of rice, as also in the three medium early varieties T. 3, T. 12, T21 of Uttar Pradesh (Misra, 1953) grown throughout their life period under naturally prevailing warm temperature, short days did not induce earliness but rather they greatly prolonged the time of ear emergence, which indicates that Kar's generalization needs modification. While studying the effect of long days on these early varieties, it was seen that long days brought about a delaying effect in ear emergence. On the basis of their flowering behaviour as related to length of day these early varieties may be classified as intermediates since these flower within a definite range of length of day, producing flowers less readily when the days are either sufliciently shortened on the one hand or sufliciently lengthened on the other (Allard, 1938; Allard & Garner, 1940). Eguchi (1937), however, has classifled certain Japanese varieties of early rice as day neutral. The average number of tillers and leaves per plant in these early varieties decreased markedly in the prolonged short-day set and in the 30-day set only as long as the treatment was operative. After the expiry of the treatment tillering and consequently the

9 Photoperiodism in rice 3-7 leaves increased considerably. Average height of the plant was adversely affected only in the prolonged treatment and that, too, at the later stages of plant growth. Short days for a month in these varieties increased the average number of panicles, panicle length, spikelets, grains, grain yield and weight of 1000 grains, but slightly depressed the percentage of grains set per panicle, while prolonged short-day treatment brought about a significant reduction in all these characters. SUMMARY Short days of 10 hr. were applied to four early (summer) varieties of rice of Uttar Pradesh to i8-day-old seedlings for i month in one set and this application was prolonged till ear emergence in another. In both the sets there was a significant delay in the ear emergence in comparison with the controls. In some cases, in addition to delaying effect, the ears were entirely suppressed and did not emerge out of the boots. When 24 hr. long days were given to two of these varieties for 20 and 30 days there was a similar delay in ear emergence. Short days for i month in these varieties increased the average number of panicles, panicle length, spikelets, grains, grain yield and weight of grains, but slightly depressed the percentage of grain setting. The prolonged short-day treatment, on the other hand, brought about a significant reduction in all these characters. Grateful thanks are due to Prof. Shri Ranjan for his guidance and helpful criticism and the facilities that he provided at the Botanical Laboratory of the University of Allahabad for carrying out this piece of investigation. I am also thankful to Mr T. P. Abraham, former Statistician, Central Rice Research Institute, Cuttack, for his advice with regard to the statistical analyses of the experimental data, to Mr C. M. Bastia for his help in the preparation of the diagrams and to Prof. B. Samantarai for offering suggestions to improve the manuscript. REFERENCES ALAM, M. (1940-1). The effect of light on the time of flowering and fruiting in rice. Det. Sci. Report, Rice Research Station, Sabour, Bihar, pp ALLARD, H. A. (1938). Complete or partial inhibition of flowering in certain plants when days are too short or too long. jf. Agric. Res. 57, ALLARD, H. A. & GARNER, W. W. (1940). Further observations on the response of various species of plants to length of day. Tech. Bull., U.S. Dep. Agric. no. 727, 64 pp. EGUCHI, T. (1937). Effects of the day-length upon the time of differentiation of flower bud and the subsequent development to flowering. Proc. Imp. Acad. Japan, 13, (Original not seen.) KAR, B. K. (1946). Vernalisation of crops cultivated in India. Nature, Lond., 157, 811. MiSRA, G. (1951). Photoperiodic response in some early varieties of paddy. Curr. Sci. 20, MiSRA, G. (1953). Photoperiodic behaviour of medium-early varieties of rice. Science, 118, MiTRA, A. K. & GUPTA, P. S. (1945). Production of more rice per acre in the United Provinces. Indian Fmg, 6, PURVIS, O. N. (1934). An analysis of the influence of temperature during germination on the subsequent development of certain winter cereals and its relation to the effect of length of day. Ann. Bot., Lond., 48, SARAN, A. B. (1945). Studies on the effect of 'short' and 'long day' treatment on the growth period and the flowering dates of different paddy varieties. J. Indian Bot. Soc. 24, SARAN, A. B. (1950). A preliminary note on the minimum period of 'short-days' required for early heading in paddy and its application under fleld conditions. J. Indian Bot. Soc. 29, SEN, B. (1940). Vernalisation. Indian Fmg, i, SIRCAR, S. M. (1939). Some aspects of vernalisation. Sci. & Cult. 4,

10 38 GADADHAR MISRA SIRCAR, S. M. (1942). Studies in the physiology of rice. II. Photoperiodic response in one variety of winter paddy. J. Indian Bot. Soc. 21, SIRCAR, S. M. (1946). Studies in the physiology of rice. III. Vernalisation by short days. Proc. Nat. Inst. Sci. {India), 12, SIRCAR, S. M. & GHOSH, B. N. (1947). Effects of high temperature and short days on vernalisation response of summer varieties of rice. Nature, Lond., 159, 605. SIRCAR, S. M. & PARIJA, B. (1949). Studies in the physiology of rice. V. Vernalisation and photoperiodic response in five varieties. Proc. Nat. Inst. Sci. (India), 15, WANSER, H. M. (1922). Photoperiodism of wheat; a determining factor in acclimatization. Science (N.S.), 56,

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