Bauhinia Acuminata

299 NON-GENETIC POLYMORPHISM IN BAUHINIA A C U3 'IINA TA L BY K. R. DRONAMRAJU Indian ,5'lalislica[ Institute, 6'alcttlla-.'~5 (Received i0-11-59) INTRODUCTION In the year 1958 Professor J.B.S. I-Ialdane suggested that I should look for heterostylism in Indian plant species where it had not previously been observed. I found a condition resembling it on a bush ofBa:~hinia acuminal,a L. This however differs fi'om the hetero- styIism so far reported in three respects. First, long and short styled flowers are found on the same plant; secondly the lengths of the filaments of the two flower types are not negatively correlated with the style length; and thirdly, most, if not all of the short styled flowers, are female sterile, i began measuring the styles on this bush in tl~e middle of the flowering season, and the results encouraged me to measure them on four other bushes of the same species. A bush can produce up to 50 flowers in a day, so it was possible to compare the results on different bushes, and on the same bush at difl'erent times. ]~ATERIAL The members of the species Bauhblia acumiTmla L. are leguminous plants belonging to the subfamily Caesalpineae. They have woody upright stems growing to a height of 12 feet. The leaves consist of 2 leaEets joined to form a single leaf with two lobes at the apex. The flowers are white and solitary, and very conspicuous, making the bush attractive in a garden. The 5 petals are slightly unequal in size. The stamens number 10, but those of the inner whorl are usually smaller and sterile (Fig. I a, b). The pods are thin and flat, and contain 10-14 fiat seeds. Two bushes (Nos. I & II) ~fB. acuminata L. growing in the compound of 902 Barrack- pore Trunk ]Load, of the Indian Statistical Institute, and three (Nos. 111, I~v( & V) growing in 204 Barrackl)ore Trunk Road, were numbered in the order in which collections ~a,ere started. All the opened flowers produced on each bush were picked daily between 08.30 and 09.30 hours in thc morning, and the styles were measured while the flowers remained fiesh. The periods d.uriug which these daily collections were made are shown in Table ] and iaclude the last days ofthe flowering seasol~. After removing the petals and stamens thc flower was placed horizontally on a millhnetre scale; and the distance between the end of the ovary where this is seen to narrow and the stigmatic expansion was measured. The length was recorded to the nearest millimetre. The style was straightcned fully on the scale before reading the measurement. In flowers where the style was much distorted m- ben t, a thread was also used to aid in the measure- mere. In 1960 a few petals and stamens were also measured in the same way. 300 F/ora[ pol3,morphi.s'~ it~ Bauhinia acuminata Fig. I. Baultitda ac~uuiuala L (a) long s@ed flower (b) shorl styled flowtr Table I Tree Number I II [II IV V Date /st examined 27.7 27.7 !I.8 I3.8 I4..8 No. of days examined 115 115 69 39 79 1-~ESULTS The flowers are grouped according'to their styJe le~gths as shown in TabIe 2, and the bimodality demonstrated in Fig. 2. There were no flowers at 11 ram, and the division: K. R. DlZONAMRAJU 301 Table 2 .~.-'urfJ'Dcr of Flowers on Slyle Iength in ( millimctres ] II II1 IV V 27 0 ] 0 0 0 "26 1 4 0 0 0 25 I7 14 0 0 3 24 33 29 6 ] 3 23 72 61 20 3 8 22 151 120 35 10 38 21 254 180 40 17 47 20 316 242 71 3t 72 19 141 93 39 28 29 18 112 82 25 18 ]3 17 IGO 56 17 6 2 16 24 12 0 0 0 15 41 25 0 0 0 14. 10 7 0 0 0 13 1 0 0 0 0 I2 3 1 0 0 0 Total with long styles 1276 927 253 114 215 mm 11 0 0 0 0 0 10 2 I 0 0 0 D 0 0 1 0 0 8 18 4 5 1 1 7 35 15 5 1 3 6 33 3 7 1 1 5 100 37 12 4 2 4. ~7 25 21 9 3 3 83 20 13 t0 '2 2 49 10 10 6 2 Tolal wldl short styles ,I07 115 74 32 14. Percentage wilh short styles 24..2 J: l "2 I 1.04-I 0.9'7 22'6:L:- 2.3 21-9:L-3"4 6.1 -:" 1.6 JO_" 9 Floral I}o!~,mor2hs il7 Bauhilaia acuminata '2 3 4 5 6 7 ~ 9 10 1l I2 13 l,I. 15 !6 [7 18 19 20 2t '22 23 2:t- 25 Jqg. 2. Bimr~dat clislt'ibul.lt~ns of slvle IengtI~s in f~ushc~ [-V. N[iIlirnctvcs K. R. D~ONAM~,JV 303 G'J ~ // i J J \ \ \ \ \ \ ,\..< \ \ \ \\\\ p,. N , \\\\ ,\\\ / Fig. 3. Perct:mages o['lvl~g ~lyicd llo',vr in 10-day periods. Bushes I (,--) ar, d I1 (' - - - ) comp,-',,rcd. 304 F/oral pd.y,~orphis,z itz Bauhinia acuminata t~o !\ \\\ -, \ , /,/-ll r, 2 I "7 /y'jr// f / J // I / / f I. / f I / / / f / r I F p r , Fi S. 4. Mean Icngd~s o~iong styled tlowcrs in i0-day pc~'i~ds. Bushes I (--) and II (- - -) COITl[}~.l.l'od' K. R. DRONAMRAJU 305 into long and short styled flowers is based on this observation. This is fiu'ther supported by the occurrence of very few flowers of style lengths around 11 ram. Thus the total lmmbers of flowers obtained fiom all the five bushes were I, 4, 3 and i for styte lengths 13ram, 12ram, 10ram and 9ram respectively. Bushes I and II flowered for about t 15 days fi'om the date they were lirst examined, and produced i683 and 1042 flowers respectively. They thus provided enough data for an analysis of the variation on the same bush and between the two bushes. The flowering period was divided into groups of I:ep. days; and the mean maximum and minimum tempm[atures, the mean rainfaI1 and the two mean style lengths of the two sorts of flowers were calculated for each period (Table 3). Similar analysis of data has been made for bushes III, IV and V, but is not pubIished and is less meaninjul because of the smaller numbers of flowers measured. The proportion of long styled flowers altered much through the season (Fig. 3) and on bushes IV and V no short styled flowers were produced for periods of ten to twelve days consecutively. The lowest percentage 0flong styled flowers was found on bush I, and the highest on bush V (Table 2). When all the five bushes are compared over the same period plants I, III andlVdo not differ significantly, but II and V differ from the rest and from one another significantly. The mode for the lengths of tong styles is at 20ram in all the five bushes (Fig. 2). The mode for short styles is at 5mm in I and II. In III this is at 4ram, in IV at 3ram and in V at 7ram and 4ram (Fig. 2). This deviation of the modes for short styles in bushes III, IX/" and V from those of I and II is possibly because very small numbers of flowers were obtained from them. This is partly due to the fewer days of flowering period observed and partly to the differences in the fi'action of short styled flowers produced by the plants. The mean lengths of the long styles in ali the five bushes rose at first and later fell to a minimum at the season's end (Fig. 4.). In I, II and V the highest mean corres- ponds to the hottest period in that part of the flowering season observed. The mean lengths of the short styles in all the five bushes fluctuated a good deal through the period 0f observation. No relation was noticed between the raini2dl and the mean style length and its variance. No order has yet been recognized in tlle position of the two types of flowers on any of the five bushes. As the season progressed the mean length of long stvJes s rows a slight rise and later a Fall which shifted the distribution nearer to thc mean lengths of short styles. If we cousider Bush No. I (Fig. 5), there were i14 flowers at 20ram and 8 flowers at 17ram for the first 20 days of the flowering period obser4-ed. But in the last 20 days there were 49 flowers at 17mm and only 10 flowers at 20ram. FURTHER COMPARISON OF TI-IE 'r~WO KINDS O1,' FLO\.VERS [[: had. seemed tha t other parts o[" short stylcd flowers were also relatively smaller than tl~ose of long styled {lowers; so in 1960 I made a few mcasureme:nts of petals and stamens (Table q.). The length of a petal was measured alol:g its :midrib. The breadth was measured on a line perpendicular to the midrib, passing through its mid poil~t. Tlm ftlament length was measured after removing the anthers. Table 4 gives the means of 306 Flottd 2u~,}~o~/~is]~z i~t Bauhinia acumim~(a -H -II -I-I -t-I -H -~-! -I-I -H -H c.'.,I r C:+ "~ ~ ~ C.O "if+ C<3 F~.

Load more