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Germination Behaviour in Dimorphic Seeds of Melothria maderaspatana L.
Flora 170,351-353 (1980)
Germination Behaviour in Dimorphic Seeds of M elothria maderaspatana L. G. S. TANWAR and D. N. SEN Laboratory of Plant Ecology, Department of Botany, University of Jodhpur, India
Summary In Melothria madeJ'aspatana (Cucurbitaceae) two types of seeds, white and black, were obscrved. White seeds were smooth and lighter in weight than black ones, which were heavier and not so smooth. These two types of seeds showed differences in rate of germination. The weight differences appear to be associated with the seed coat hardness and thus their germinability.
The germination behaviour of the seeds of a number of plants has been found to be of considerable importance in deciding their distribution. WENT (1949) stated that summer and winter vegetation of annuals in deserts is principally due to the differential rate of seed germination. The variability of seed size and weight which may be controlled by specific genetic constitution, is often influenced by internal competition for food during embryo development and seed maturation. There are reports of acute competition between flowers for substrate materials responsible for some embryos in the upper part of the inflorescence for not developing into seed as seen in Echinops echinatus (PANDEY 1968). The difference in size and weight of the seeds, tending to ensure more efficient segregation in their dispersal (SALISBURY 1942), is therefore, of great ecological significance in the distribution of many plant species.
Materials and Methods Melothl-ia maderaspatana is one of the most variable among the Indian desert plants. It is a very common plant throughout the area, climbing over bushes and creeping in open places. Mature fruits of ]}t. maderaspatana were collected in October 1978. The seeds were taken out from the fruits, air dried and stored. Two types of seeds were observed viz. white and black ones. The differences in the dimensions of the seeds were noted. Germination studies were carried out in sterilized petridishes lined wit,h a single layer of filter paper, moistened with distilled water. The criterion for imbibition was the swelling of the seeds, and that for germination, the protuberence of the radicle. Petridisheg were placed under light of lOOO lux in a growth room at different temperatures ranging from 26 - 34 cC. Each set was run in triplicate, and eaeh petri dish contained 20 seeds. 23a
352
G. S. TAXWAR and D.
~. SEX
Results and Discussions The dimensions of the white and black seeds were similar but they differed in their weights. The white seeds were lighter than the black ones (Table 1). The percentage of germination was high in white seeds and low in black ones (Table 2). The germination percentage decreased with increasing high temperatures (Table 2), i.e., optimum germination was observed at 26 °0 and mi nimum percentage germination was at 34 °0. Table 1. Dimension, seed shape index (length/breadth ratio) and weight in dimorphic seeds of M. maderaspatana Seed dimension (mm) Seed
Average length
Average breadth (b)
(1)
White Black
4 4
± ±
0.08 0.08
3 3
± ±
0.67 0.67
Seed index (lib)
Average seed weight (mg)
1.33 ± 0.13 1.33 ± 0.13
5 11
± ±
Seed density unit which .025 .055
0.12 0.37
± ±
0.06 0.09
Table 2. Percentage germination under different temperatures at the end of 14 days, in dimorphic seeds of M. maderaspatana 'l'emperature in °C 26 White seeds Black seeds
37 30
± ±
3.4 3.3
28
30
30 ::f: 2.4 20 ± 2.2
25 15
32
± ±
2.0 1.9
15 10
34
± ±
1.9 1.6
10 5
± ±
1.6 1.4
WILLIAMS and HARPER (1965) have demonstrated that polymorphic seeds differed in their germination requirements. SEN (1968) reported two forms in Euphorbia caducifolia. The seeds from eight individual plants showed difference in seed coat patterns and also in germination behaviour. SALISBURY (1942) has recognized the possibility of a difference in seed weight between two different strains of the same species. Such a difference in seed weight has been discernible in the two ecotypes of Euphorbia hirta and Setaria glauca (RAMAKRISRNAN 1960, 1963). ORATTERJI and SEN (1964) have observed two types of seeds, the heavier ones showed a better germination percentage than those which were lighter and floating in water in Salmalia malabarica. In Echinops echinatu8, PANDEY (1968) classified the seeds into 5 categories on the basis of their weights, out of which the heavier ones showed high percentage of germination in 24 h. AMBAsRTandMAURYA(1970~ correlated the reduction in percentage germination with the reduction in weight in individual seeds of Dichanthium annulatum in grazed grounds. BORRA and SEN (1974) observed three types of colour patterns in the seed coat of Crotalaria medicaginea i.e., dark-black, yellowish-black and yellow. Freshly har-
Germination Behaviour in Dimorphic Seeds
353
vested seeds did not exhibit any hard seed coat dormancy, but this appeared to develop when they were fully dried. BANSAL and SEN (1978) recognized two categories of the seeds in Cucumis callosu8 on the basis of fruit and seed size, number of seeds per fruit, and the weight of seeds. They also observed that optimum germination was obtained in total darkness. A somewhat similar situation has been recorded in the seeds of Ipomoea pes-tigridis and I. sindica where seeds from four localities varied a great deal in colour, size and germination percentage (BHAT! and SEN 1978). In the present investigation, optimum germination was observed in white seeds which were lighter in weight as compared to heavier black seeds, although PANDEY (1968) has reported that heavier seeds in Echinops echinatu8 showed a higher germination percentage.
References AMBASHT, R. S., and MAURYA, A. N.: Reproductive capacity of Dichanthium annulatum STAPF. in relation to biotic factors. Trop. EcoI. II, 186-193 (1970). BANSAL, R. P., and SEN, D. N.: Contribution to the ecology and seed germination of Oucumis callosus. Folia Geobot. Phytotax. 13, 225-233 (1978). BHATI, P. R., and SEN, D. N.: Adaptive polymorphism in Ipomoea pes.tigridis (Oonvolvulaceae), a common rainy season weed of the Indian Arid Zone. PI. Syst. & EvoI. 129, 111-.117 (1978). BOHRA, P. N., and SEN, D. N.: Seed patterns and germination behaviour in Orotalaria medicaginea LAMK. growing in Indian arid zone. Curro Sci. 43, 591-592 (1974). OHATTERJI, U. N., and SEN, D. N.: On the ecophysiology of Salmalia malabarica (DC.) SCHO & ENDL. seeds. Sci. & Cult. 30, 598-600 (1964). PANDEY, S. B.: Germination and seedling mortality in Echinops echinatu~ RoxB. Proc. Symp. Recent Adv. Trop. EcoI. pp. 237-244 (1968). RAMAKRISHNAN, P. S.: Studies in the autecology of Euphorbia hirta LINN. J. Indian bot. Soc. 39, 455-473 (1960). -
Contribution to the ecological life history of Setaria glauca BEAUV. J. Indian. bot. Soc. 42, 118-129 (1963).
SALISBURY, E. J.: The Reproductive Capacity of Plants. London 1942. SEN, D. N.: Leafless Euphorbia on Rajasthan rocks. II. Seed germination and seedling growth in Euphorbia caducifolia HAINES. Proc. Symp. Recent Adv. Trop. Ecol. pp. 202-212 (1968). VV~JNT, F. W.: Ecology of desert plants. II. The effect of rain and temperature on germination and growth. Ecology 30,1-13 (1949). VVILLIAMS, J. T., and HARPEH, J. L.: Seed polymorphism and germination. 1. The influence of nitrates and low temperature on the germination of Ohenopodium album. Weed Res. 5, 141 -150 (1965). Received March 12, 1980. Authors' address: G. S. TANWAH and D. N. SEN, Department of Botany, University of Jodh. pur, Jodhpur - 342 001, India.
Germination Behaviour in Dimorphic Seeds of M elothria maderaspatana L. G. S. TANWAR and D. N. SEN Laboratory of Plant Ecology, Department of Botany, University of Jodhpur, India
Summary In Melothria madeJ'aspatana (Cucurbitaceae) two types of seeds, white and black, were obscrved. White seeds were smooth and lighter in weight than black ones, which were heavier and not so smooth. These two types of seeds showed differences in rate of germination. The weight differences appear to be associated with the seed coat hardness and thus their germinability.
The germination behaviour of the seeds of a number of plants has been found to be of considerable importance in deciding their distribution. WENT (1949) stated that summer and winter vegetation of annuals in deserts is principally due to the differential rate of seed germination. The variability of seed size and weight which may be controlled by specific genetic constitution, is often influenced by internal competition for food during embryo development and seed maturation. There are reports of acute competition between flowers for substrate materials responsible for some embryos in the upper part of the inflorescence for not developing into seed as seen in Echinops echinatus (PANDEY 1968). The difference in size and weight of the seeds, tending to ensure more efficient segregation in their dispersal (SALISBURY 1942), is therefore, of great ecological significance in the distribution of many plant species.
Materials and Methods Melothl-ia maderaspatana is one of the most variable among the Indian desert plants. It is a very common plant throughout the area, climbing over bushes and creeping in open places. Mature fruits of ]}t. maderaspatana were collected in October 1978. The seeds were taken out from the fruits, air dried and stored. Two types of seeds were observed viz. white and black ones. The differences in the dimensions of the seeds were noted. Germination studies were carried out in sterilized petridishes lined wit,h a single layer of filter paper, moistened with distilled water. The criterion for imbibition was the swelling of the seeds, and that for germination, the protuberence of the radicle. Petridisheg were placed under light of lOOO lux in a growth room at different temperatures ranging from 26 - 34 cC. Each set was run in triplicate, and eaeh petri dish contained 20 seeds. 23a
352
G. S. TAXWAR and D.
~. SEX
Results and Discussions The dimensions of the white and black seeds were similar but they differed in their weights. The white seeds were lighter than the black ones (Table 1). The percentage of germination was high in white seeds and low in black ones (Table 2). The germination percentage decreased with increasing high temperatures (Table 2), i.e., optimum germination was observed at 26 °0 and mi nimum percentage germination was at 34 °0. Table 1. Dimension, seed shape index (length/breadth ratio) and weight in dimorphic seeds of M. maderaspatana Seed dimension (mm) Seed
Average length
Average breadth (b)
(1)
White Black
4 4
± ±
0.08 0.08
3 3
± ±
0.67 0.67
Seed index (lib)
Average seed weight (mg)
1.33 ± 0.13 1.33 ± 0.13
5 11
± ±
Seed density unit which .025 .055
0.12 0.37
± ±
0.06 0.09
Table 2. Percentage germination under different temperatures at the end of 14 days, in dimorphic seeds of M. maderaspatana 'l'emperature in °C 26 White seeds Black seeds
37 30
± ±
3.4 3.3
28
30
30 ::f: 2.4 20 ± 2.2
25 15
32
± ±
2.0 1.9
15 10
34
± ±
1.9 1.6
10 5
± ±
1.6 1.4
WILLIAMS and HARPER (1965) have demonstrated that polymorphic seeds differed in their germination requirements. SEN (1968) reported two forms in Euphorbia caducifolia. The seeds from eight individual plants showed difference in seed coat patterns and also in germination behaviour. SALISBURY (1942) has recognized the possibility of a difference in seed weight between two different strains of the same species. Such a difference in seed weight has been discernible in the two ecotypes of Euphorbia hirta and Setaria glauca (RAMAKRISRNAN 1960, 1963). ORATTERJI and SEN (1964) have observed two types of seeds, the heavier ones showed a better germination percentage than those which were lighter and floating in water in Salmalia malabarica. In Echinops echinatu8, PANDEY (1968) classified the seeds into 5 categories on the basis of their weights, out of which the heavier ones showed high percentage of germination in 24 h. AMBAsRTandMAURYA(1970~ correlated the reduction in percentage germination with the reduction in weight in individual seeds of Dichanthium annulatum in grazed grounds. BORRA and SEN (1974) observed three types of colour patterns in the seed coat of Crotalaria medicaginea i.e., dark-black, yellowish-black and yellow. Freshly har-
Germination Behaviour in Dimorphic Seeds
353
vested seeds did not exhibit any hard seed coat dormancy, but this appeared to develop when they were fully dried. BANSAL and SEN (1978) recognized two categories of the seeds in Cucumis callosu8 on the basis of fruit and seed size, number of seeds per fruit, and the weight of seeds. They also observed that optimum germination was obtained in total darkness. A somewhat similar situation has been recorded in the seeds of Ipomoea pes-tigridis and I. sindica where seeds from four localities varied a great deal in colour, size and germination percentage (BHAT! and SEN 1978). In the present investigation, optimum germination was observed in white seeds which were lighter in weight as compared to heavier black seeds, although PANDEY (1968) has reported that heavier seeds in Echinops echinatu8 showed a higher germination percentage.
References AMBASHT, R. S., and MAURYA, A. N.: Reproductive capacity of Dichanthium annulatum STAPF. in relation to biotic factors. Trop. EcoI. II, 186-193 (1970). BANSAL, R. P., and SEN, D. N.: Contribution to the ecology and seed germination of Oucumis callosus. Folia Geobot. Phytotax. 13, 225-233 (1978). BHATI, P. R., and SEN, D. N.: Adaptive polymorphism in Ipomoea pes.tigridis (Oonvolvulaceae), a common rainy season weed of the Indian Arid Zone. PI. Syst. & EvoI. 129, 111-.117 (1978). BOHRA, P. N., and SEN, D. N.: Seed patterns and germination behaviour in Orotalaria medicaginea LAMK. growing in Indian arid zone. Curro Sci. 43, 591-592 (1974). OHATTERJI, U. N., and SEN, D. N.: On the ecophysiology of Salmalia malabarica (DC.) SCHO & ENDL. seeds. Sci. & Cult. 30, 598-600 (1964). PANDEY, S. B.: Germination and seedling mortality in Echinops echinatu~ RoxB. Proc. Symp. Recent Adv. Trop. EcoI. pp. 237-244 (1968). RAMAKRISHNAN, P. S.: Studies in the autecology of Euphorbia hirta LINN. J. Indian bot. Soc. 39, 455-473 (1960). -
Contribution to the ecological life history of Setaria glauca BEAUV. J. Indian. bot. Soc. 42, 118-129 (1963).
SALISBURY, E. J.: The Reproductive Capacity of Plants. London 1942. SEN, D. N.: Leafless Euphorbia on Rajasthan rocks. II. Seed germination and seedling growth in Euphorbia caducifolia HAINES. Proc. Symp. Recent Adv. Trop. Ecol. pp. 202-212 (1968). VV~JNT, F. W.: Ecology of desert plants. II. The effect of rain and temperature on germination and growth. Ecology 30,1-13 (1949). VVILLIAMS, J. T., and HARPEH, J. L.: Seed polymorphism and germination. 1. The influence of nitrates and low temperature on the germination of Ohenopodium album. Weed Res. 5, 141 -150 (1965). Received March 12, 1980. Authors' address: G. S. TANWAH and D. N. SEN, Department of Botany, University of Jodh. pur, Jodhpur - 342 001, India.