6

REVIEW OF LITERATURE 7

" Review of Literature"

The family is little known from the view point of karyomorphology# despite the larger number of species distributed widely. It is of the special interest to note that only about 9x/^% of the total number of species available in this family has so far been cytologically investigated# and even where the chromosome numbers have been determined

(ef. Darlington and Wylie# 1955; Fedorov#1969)# the knowledge concerning the details of karyotype pertaining to chromosome measurements which are vital to the understanding of karyological affinities# is still meagre. There are few reports of karyotypes of the members of this family (Sharraa and Chatterji#1957;

Sharma and Datta#1958; Nakajima#1963; Sampathkumar#1970;

Kaul and Bhan#1974; Vij et al.,1977; Sampathkumar#1979).

Cytological studies in the family are mainly concerned with chromosomal numbers (cf. Darlington A. and Wylie# 1955). The basic number X5*^ characterizes A J the genera Quamoclit# Argyreia# Calonyction# Hewittia# V Merreraia# Operculina# Stictocardia and , A Polyploidy has also been observed in the family # V particularly allopolyploidy and often segmental

(Chatterjee and Nagbiswas#1952; Stebbins# 1950).

Sharraa and Datta (1958) studied 24 differen species and varieties of Ipomoea with a view to provide solution

Ipoiaoea semperflorence 2n=40 and I. coccinea 2n=28

and noted a gross resemblance in general# in karyotypes

of different species of Ipomoea# and supported the

classification of Hooker (1885) for Ipomoea. They

further suggest that all the present species of

Ipomoea have been derived from n=14 or n=15 chromosomes and most of the diversification of the species have

resulted from a level of n=15 chromosomes.

Vij et al.#(1977) studied the cytomorphological

studies in the genera of family Convolvulaceae.

Polyploid nature of Ipomoea batata and some desynaptic

bivalents in Merremia aegypta also accounted for

aberrant meiosis. They have reported some desynaptic bivalents in Ipomoea bonanox# I. charyseoides# n=15#

I. mutabilis n=15+0~lB# I. dichroa n=15 and I. galmata (White flowered type n=15+lB). Lowest and highest

chromosome numbers n=9 and n=45 were encountered in

Jacquemontia pentantha and Ipomoea batata# respectively.

However they have discussed importance of aneuploidy

and polyploidy in the evolution of Convolvulaceae. They have correlated morphological variability with

cytological features in # I. eriocarpa

and I. palmata. The genus Jaequemontia, according to the reports available in the literature, has both 2n=18 as well as 2n=20 chromosomes. (Robertson,1970;

Lewis and Oliver, 1970? Vij et al.,1977 & Jones, 1968).

The chromosomes of Jaequemontia are larger than those of the species of IpomOea. The unusual number, namely,

2n=18 in J aequemontia, with long chromosomes and high absolute chromosome length, suggest a special line of evolution being a primitive number of the family.

It is suggested that n=10 is derived from n=9, in view of the preponderance of this number (n=9).

The genus Argyreia has two sections namely, Euarqyreia and Pomifera (Hooker,1885). The chromosomes of Argyreia in general are comparatively of larger in size than those of many species of Ipomoea. The chromosome numbers of Argyreia argentea and A. campanulata have been known to be 2n=28 (Sharraa and

Chatterji,1957; Vij et al.,1974)* while that of

A. nervosa 2n=30 (Watanabe,1939).

Sharma and Chatterji,(1957), Kaul and Bhan,

(1974) noted that cuscuta, with its usually long chromosomes and their large number in different species (as compared with other members of the family even at a polyploid level) seems to stand apart from the rest of the genera in the family. ! f 10

Fritsch and Reinhard, (1972) have reported

2n»3Q in .

Sampathkumar (1979) in his extensive study of karyomorphology of some south Jndian Convolvulaceae members# reported the chromosome numbers in the following genera.

Argyreia cuneata 2n=30# A. hirsuta 2n=30;

Cuscuta chinensis 2n=56; Hewittia sublobata 2n=30; 2n=30# I. aquatica 2n=30#

I. cairica 2n=30, crassicaulis 2n=30,

■aI. aiHMiiaMBaMaNMMan*conqesta 2n=30, I. aMataaaaaaacoptica 2n=28# I. hederifolia 2n=28, I. tuba 2n=30# I. maxima 2n=30# I. muricata 2n=30# I. nil 2n=30, I. obscura 2n=30#

I. pes-caprae 2n=30# I. pes-tigridis (unlobed) 2n=28#

I. PPPPPPea 2n=*32# I. guamoclit 2n=30#

I. staphylina 2n=32; Jacquemontia pentantha 2n=18; Merremia dissecta 2n=32# M. hederacea 2ri=30;

Operculina turpethum 2n=30; Rivea hypocrateriformis 2n=30.

On the basis of detailed karyological investigations in over 43 taxa of Convolvulaceae

(Sarapathkumar#1970#1979? Sampathkumar and Ayyangar, 1981) karyophyletic trends in the family were brought out.

A case was presented for the generic merger of Rivea with Arqyreia on a critical analysis of karyomorphological data. Family status for Cuscuta co-ordinate with 11

Convolvulaceae was also suggested. Apart from the basic chromosome numbers other aspects studied were features of pollen and cotyledonary characteristics.

On these grounds# it was proposed (Sampathkumar and

Ayyangar#1981) that Eyolvulus and Creasa deserved to be upgraded to distinct tribes# Evolvuleae and Cresseae respectively.

Sampathkumar (1982) has reported the usefulness of the cotyledonary leaf characteristics in the of Convolvulaceae. Certain characters of the mature cotyledonary leaves of seedlings# such as the mean area# depth of lobing# depth of basal sinus# angle between the lobes# pattern of venation# stalk length and other features offer much scope for the taxonomists# in view of their high level of constancy. Furthermore# being quite conservative# these characters shed considerable light on the systematic relationship existing among the taxa. The cotyledonary leaves of

Merremia tridentata are very similar to those of

Ipomoea Coptica# suggesting parallel evolution. Among the varieties of I. nil and I. batatas# there exist certain differences# while the two varieties of I. pes-tiqridis register greater similarity, ^volvulus alsinoides and E. nummulaAius show but a slight difference in size.

Cressa cretieff, is unique in having linear cotyledons. 12

Cuscuta ehinensis stands apart from the rest of the family, being acotyledonous, thus affording yet another reason for its segregation from Convolvulaceae.

Rivea hypocrateriformis and Argyreia cuneata show similar characteristics, giving additional support in favour of the genetic merger of Rivea with Argyreia.

The morphology and distribution of the petiolar nectaries in Ipomoea had been studied by Keeler et al. (1979).

Leal et al.,(1975) studied the leaf anatomy of

Ipomoea cynanchifolia and reported certain distingushing features like broad cuticles with epicuticular strials; dorsiventral type mesophyll; secretary cells, long tectorial hairs and glandular hairs; calcium oxalate crystals^ in the and in the blade. However, the thick cuticular striations form distinct patterns in

1* different species and this can be usedAdistinguish various species of Ipomoea (Srivastava et al.,1983).

Brown (1938) described the nectary (£ as a disc often attached to the base of the ) as characteristic of the Polemoniales, Boraginales, etc.

Fahn (1952,1953) in his survey of the nectaries in flowering describes those in the Convolvulaceae as discoidal, the nectary is a disc surrounding the base of the ovary. Furthermore, there exists an acro-centripetal succession in the location of the nectaries from the outer floral whorls to the gynoecium Keeler et al.,(1977,1978,1980) have described the two types of extrafloral nectaries in Ipomoea leptophyla located on the petiole and on the pedicel.

Woodcock (1943) reported that in Ipomoea the ovule has no distinct integument and the micropyle is formed by an "investigation1* is also due to a misinterpretation. As in other members of the

Convolvulaceae (Maheshwari,1944), an integument is present and it is the nucellus which soon disappears.

The micropyle is not an investigation but a continuous passage, which begins to be more or less occluded in post fertilization stages and is therefore difficult to demonstrate in nonmedian sections.

Tiagi (1951) finds that, erabryologically, the genus cuscuta is best retained in the family

Convolvulaceae. The anatomical observations on the fertilization and embryogenesis in , (Ipomoea batata) had been studied by Kokubu, et al.(1982).

The rapid rolling up of the ephemeral morning-glory

() flowers is the result of differential growth of tissues within the ribs (Richner and Matile,

1977). Electron microscopical and light miscroscopical studies in Ipomoea tricolor have shown that there are structural changes in the inner epidermal cells which affect the turgor status of the cells and initiate the opening and eventual closing of the flower pmillips et al,1980)

Ennos and Clegg (1983) studied the flower colour variation in the morning-glory, . It is strikingly polymorphic for flower colour. Eight colour phenotypes are commonly found. Flower colour variation can be accounted for segregation at the three loci. The inheritance of a mottled phenotype and of esterase variation are also reported. Variation in the flower colour influences pollinat&cnbehaviour and maternal out crossing rates. These highly polymorphic populations may provide an ideal opportunity for

'■4" studing evolution of the mating system. K Erdtman (1952) considers the pollen grains of the

Convolvulaeeae under two distinct categories, one of which is described as the Ipomoea type.

Sayeeduddin et al. (1942) described the pollen of a species of Ipomoea. Nair and Rehman (1963) concur with Erdtman in the categorisation of the pollen types. They also find that the pollen grains can be used profitably in the taxonomy of the family.

Palynological studies were made by Vij et al„( 1974) in 31 species and revealed a multipalynous character of the family Convolvulaeeae. The shape of the pollen 15

grains varied from prolate-subprolate to prolate spheroidal and showed a great range in size variation.

The smallest grains were seen in Porana paniculata while the largest in . Pollen grains of Ipomoea fistulosa were observed as pantoporate type.

Parveen et al. (1982) described the palynological account in seven genera viz# .Convolvulus# Cressa#

Merremi a# Eyolvulus# Argyrei a# Ipomoea and Rivea and 23 species of Convolvulaceae found in India)^esert.

Pollen morphology in relation to taxonomy of the family

Convolvulaceae is also discussed.

The origin and organization of lamellae or tapes was investigated in pollen exine of ipomoea purpurea

(Gupta et al.#1983). At the tetrad stage# microspores develop highly vesicullar cytoplasm. The vesicles probably originate from golgi bodies. Gradually they move to the plasmalemma of microspore while others are

extruded out as such. Subsequently# it seems that they

are compressed forming characteristic tapes with a

central electron rate area bound by electron dense streaks on either side. Around these tapes the

carotenoids and their esters apparently polymerize# organizing the lamellar nexine.

Pollination is the main factor in fruit setting. 16

In the genus Ipomoea self-incompatibility exists and it results in poor fruit setting. Information about the nature of incompatibility in the genus Ipomoea had been given by many workers in various species (Martin#1965,

1968; Bahadur#1976; Venkateswarlu# 198G; Sood et al.# 1982).

Kowyama et al.#(1980) studied the genotypic constitutions of incompatibility in the diploid

species# Ipomoea leucantha which is most closely related to the sweet potato. Venkateswarlu (1980) has reported the floral morphology and self incompatibility in

sweet potato. The sweet potato is homomorphic with

stylar variation.

Prabha et al.#(1982) studied the high temperature

induced inactivation of sporophytic self-incompatibility

in Ipomoea fistulosa. They observed that the rate of

recovery of self-incompatibility depends on the initial

heat treatment given to the . Sporophytic incompatibility reported in can be

partially overcome under in vitro conditions by treating —5 —1 the pollen and/or stigma with 10 to 10 M IAA# the -2 optimum being 10 M. (Sood et al.#1982).

The self-incompatibility and sterility in

Ipomoea pandurata has been reported by Stucky et al.#

(1982). It rarely produces seed. Sporophytic se

self-incompatibility is a secondary factor contributing 'n 17

to the reduced seed production because the principal pollinators effect cross pollination in most populations.

Sterility expressed as a pollen tube failure in the style and as a sterility mechanism in the ovary, is the primary factor accounting for reduced seed production.

Guties, (1978) had described a major barrier to hybridization of some Ipomoea species is located at the

stigma-style interface. Attempts to facilitate hybridization among Ipomoea species using mentor pollen-foreign pollen mixes were unsuccessful.

Artificial crosses between and

I. trichocarpa produced intermediates that resembled plants found growing wild. Back-crossing of the artificial hybrids yielded on array of progeny that was

similar to wild plants. The hypothesis is presented by

Abel et al.,(1981) that Ipomoea lacunosa and

I. trichocarpa are experiencing introgressive hybridization.

Ephemeral flowers d>f Ipomoea tricolor were tested with regard to their suitability for the rapid

screening of senescence-inducing chemical compounds by

Hurter et al.,(1980).

Rao et al.,(1976) had described the effects of some growth regulators like IAA, IBA, GA, NAA, CCC & 18

CFI on the regeneration of stem cuttings of

Ipomoea fistulosa and observed disarrangement and poor lignification of the xylem. CPI may be useful ^n checking propagation of this weed. However, the increase of gibberellic activity was tested during the growth on the twining shoots of Ipomoea purpurea by Claire et al.,(1982).

The photosynthesis in Ipomoea pescaprae was studied by Joshi et al.-(1982) and found that it possesses C^ pathway & the findings have been further supported by enzyme studies.

The post-coital antifertility activity of

Ipomoea fistulosa was reported by Mishra et al.,(1979).

The principal substances Agroclavin and -dihydrolysergol from leaves of Ipomoea fistulosa were isolated and identified by Umar et al. (1980).

In the toxicological-pharmacological evalution of the alcoholic extract of seeds of Ipomoea muricata produced no significant effects on blood cellular elements (Solevilla et al., 1982).

Khare et al. (1982) have reported antiinflammatory activity of Ipomoea turpethium. Ethereal, alcoholic and aqueous extracts of roots of I. turpethium were screened

for their antiinflammatory activity against experimental inflammation to albino rats. Aqueous extract was the most potent fraction in all three models of experimental inflammation Amador et al. (1982) studied the seed oils of

Turbina eoryrabosa, , I. murucoides and I. decasperma.