In this article we will discuss about:- 1. General Features of the Solanaceae 2. Floral Range in the Solanaceae 3. Divisions 4. Position and Affinity 5. Number and Distribution 6. Commonly Occurring Plants 7. Economic Aspects.
General Features of the Solanaceae:
Habit – Herbs or shrubs, with bicollateral vascular bundles.
Leaves – Alternate, simple, exstipulate, often in unequal pairs.
Flowers – Bisexual, regular, hypogynous.
Calyx – Sepals 5, united, persistent.
Corolla – Petals 3, united, often plaited.
Androecium – Stamens 5, epipetalous; disc present: anthers apparently connate, 2-celled with a porous dehiscence.
Gynoecium – Carpels 2, syncarpous, obliquely placed’, ovary superior 2-locular or imperfectly 4-locular by a false septum; ovules many in each loculus; placentation axile.
Fruit – Berry or capsule.
Seeds – Many with a pitted testa; embryo curved or straight.
Floral Range in the Solanaceae:
In Solanum, the inflorescence is a monochasial cyme with the suppression of secondary branches on the same side. The flowers are generally regular, but irregular in Brunfelsiq, Hyoscyamus and a few other genera.
The corolla may assume various forms. It is campanulate in Atropa, infundibuliform in Datura, rotate in Solanum and bilabiate in Schizanthus.
The development of a false septum in the ovary is a frequent character in the Solanaceae. This results in the ovary being 3- to 5-celled in Nicandra and 4-celled in Datura. The vary may be 1-celled in the upper part, as in Capsicum. The number of ovules is usually many, but a few ovules are seen in Cestrum.
Divisions of the Solanaceae:
The Solanaceae is divided into two groups, one with three tribes and the other with two tribes:
Group A:
All stamens fertile. Embryo very much curved.
Tribe (i) Datureae:
Ovary 4-celled, septum dividing placenta equally. Example- Datura.
Tribe (ii) Nicandreae:
Ovary 3- to 5-celled, septum dividing placenta unequally. Example- Nicandra.
Tribe (iii) Solaneae:
Ovary 2-celled. Examples- Capsicum, Solanum. etc.
Group B:
All stamens or 2-4 stamens fertile. Embryo slightly or almost straight.
Tribe (i) Cestreae:
All 5 stamens fertile. Seeds small, not flat. Example- Cestrum.
Tribe (ii) Salpiglossideae:
Flowers zygomorphic. Stamens 2-4, fertile. Examples- Brunfelsia, Salpiglossis, etc.
Position and Affinity of the Solanaceae:
The Solanaceae was included by Bentham-Hooker as well as Bessey in the Polemoniales. Engler treated the family under the suborder Solanineae to the order Tubiflorae. Hallier regarded the family as a primitive member of the Tubiflorae and together with the Scrophulariaceae to have arisen very likely from the Linaceae.
Wettstein put the family in the Tubiflorae along with the Convolvulaceae. Rendle placed the family in the Tubiflorae, assigning a separate position for the Convolvulaceae under the Convolvulales. In Hutchinson’s arrangement, the family appeared under the Solanales which also included the Convolvulaceae and Nolanaceae.
The Solanaceae bears a close relationship with the Boraginaceae, the elements of similarity being the alternate leaves, regular flowers and pentamerous stamens. It is related to the Convolvulaceae by the presence of an intraxylary phloem, persistent calyx, twisted corolla and false septum. It is also akin to the Scrophulariaceae, but differs from the latter by the generally actinomorphic corolla, typically pentamerous stamens and obiique position of carpels.
Number and Distribution of the Solanaceae:
There are about 90 genera and 2,000-3,000 species in the Solanaceae. Though the members of the family are abundant in the tropical and temperate regions of the world, their principal centres of distribution lie in Australia as well as Central America and South America.
Commonly Occurring Plants of the Solanaceae:
Browallia americana L. is an annual garden herb, having blue or violet flowers.
Queen-of-the-night (Cestrum noctumum L.) is a garden plant with flowers emitting a sweet smell at night.
Tree-tomato [Cyphomandra betacea (Cav.) Sendtn.] is grown at hillstations for its edible fruits.
Thorn-apple (Datura metel L.) is a herb with highly poisonous seeds.
Tomato [Lycopersicon lycopersicum (L.) Karst.] is a tall herb, bearing red globose pulpy fruits.
Wild Tobacco (Nicotiana plumbaginifolia Viv.), Physalis minima L. and Solanum surattense Burm. f. are weeds.
Solanum erianthum D. Don is a small tree.
Solanum ferox L., S. indicum L. and Black Nightshade (S. nigrum L.) are herbs on road sides.
Solanum filicifolium Ort. is a shrub.
Solanum torvum Swartz is a spiny herb or shrub.
Solanum trilobatum L. is a prickly climber, being prevalent in the salt flats near Calcutta.
Economic Aspects of the Solanaceae:
Economically, the members of the Solanaceae are of great importance and yield foods, drugs and ornamentals.
The fruits of Capsicum annuum, C. fastigiatum and C. frutescens arc used as a condiment. The fruits of Cyphomandra betacea, Physalis alkekengi, P. heterophylla, P. ixocarpa and P. peruviana are edible. A number of plants are used as vegetables, e.g. Solanum melongena, S.tuberosum and Lycopersicon lycopersicum. The fruits of S. quitoense (Andes) form a refreshing beverage.
Some plants are of medicinal value. Atropa belladonna (Mediterranean) contains ‘atropine’, widely used following severe colds. Hyoscyamus niger is used as a narcotic and Withania somnifera as a nervine tonic. Alkaloids like ‘daturin’ and ‘nicotine’ are derived from Datura stramonium and Nicotiana tabacum respectively; the latter is economically outstanding as the source of tobacco leaves which are turned into cigarettes.
A few plants are cultivated as ornamentals, e.g. Brunfelsia americana, Cestrum nocturnmum, Petunia hybrida, P. violacea, Nicotiana alata, N. glauca, etc.
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