In this article we will discuss about:- 1. General Characters of Cruciferae (Brassicaceae) 2. Floral Formula of Cruciferae (Brassicaceae) 3. Number and Distribution 4. Range of Floral Structures 5. Common Plants 6. Affinity and Economic Importance.
General Characters of Cruciferae (Brassicaceae):
Plants—annual or biennial herbs, often with pungent watery latex. Leaves—radical or cauline (usually alternate), simple, more or less lobed, sometimes compound (e.g., Cardamine), ex-stipulate with 1- celled simple or branched hairs. Inflorescence—usually a raceme, sometimes corymb (e.g., Iberis), ebracteate.
Flowers—bisexual, regular (irregular in Iberis), actinomorphic, hypogynous. Sepals— 2 + 2, free, imbricate. Petals—4, free, cruciform, clawed, imbricate or twisted. Stamens—2 + 4, tetradynamous, with nectaries present at the base of long stamens. Carpels—(2); ovary superior, 1-celled with parietal placentation, but afterwards 2-celled by a false septum (replum) connecting the two parietal placentae; ovules many, campylotropous. Fruit—usually a siliqua, sometimes a silicula. Seeds— numerous, round, exalbuminous, oily with curved embryo.
Floral Formula of Cruciferae (Brassicaceae):
Number and Distribution of Cruciferae (Brassicaceae):
This family consists of 350 genera and about 2,500 species which are chiefly found in the North temperate regions and in the plains during winter.
Range of Floral Structures in Cruciferae (Brassicaceae):
The regular flowers (e.g., Brassica, Raphanus) are bisexual and hypogynous, with four free sepals in two whorls, median and transverse, and four free diagonally placed petals. The androecium is typically of 6 stamens in 2 whorls, usually tetradynamous. The pistil consists of 2 transversely placed carpels bearing a double row of pendulous, campylotropous ovules on the parietal placentae formed at two sutures.
Departures from the normal type of flower occur. In Iberis and Teesdalia the flower becomes zygomorphic by the enlargement of the two outer petals. The petals are infrequently small or absent totally, as in species of Lepidium, Coronopus, Nasturtium and others; in Capsella bursa pastoris, the petals are occasionally replaced by 4 stamens.
Reduction in the number of stamens is also found to occur. In Cardamine hirsuta, the lateral stamens are generally absent; in species of Lepidium and Coronopus doubling of the median stamens may also fail to take place and the flower ultimately becomes diandrous. In the Asiatic genus Megacarpaea, the number of stamens reaches up to 16.
Three or four carpels occur abnormally in many genera of Cruciferae. The genera Tetrapoma and Holargidium have four- (or more) carpelled ovary. Lepidium sativum represents the tricarpellary pistil. Multicarpellary pistils have also been recorded in abnormal flowers in a considerable number of genera.
The pistil sometimes presents difficulties in the almost universal position of the stigmas above the commissure, or the vertical line of tissue at the junction of the two carpels, and in the presence of false septum. In Matthiola incana and Moricandia the stigmas occupy the usual position above the midrib of the carpel.
Common Plants of Cruciferae (Brassicaceae):
(1) Mustard plants, e.g., Mustard or Indian rape (Brassica napus L.), White mustard (B. alba Hook. & Thom.), Black mustard (B. nigra Koch. = B. juncea Hook. & Thom.), are all cultivated for oil.
(2) Radish (Raphanus sativus L.), is cultivated for the swollen fleshy root.
(3) Turnip (Brassica campestris L.), is taken as a vegetable.
(4) Nasturtium indicum DC.= Rorippa indica Hochr, a weed.
(5) Candytuft (Iberis amara L.), a common garden plant.
(6) Cauliflower, cabbage, knol-kohl and broccoli are the different varieties of Brassica oleracea L., which are cultivated as vegetables.
(7) Cardamine debilis Don., a garden weed of the cold weather.
(8) Eruca sativa Lamk., a cold weather crop is occasionally cultivated.
(9) Shepherd’s purse (Capsella bursa pastoris Moench.), a common weed.
(10) Senebiera pinnatifida DC. = Coronopus didymus Sm., a common weed in garden and roadside.
Affinity and Economic Importance of Cruciferae (Brassicaceae):
Phyletically, the position of Brassicaceae is in the Rhoedales. But there are discrepancies of opinion between Bentham & Hooker and Hutchinson, as to whether it has been derived from papavarous ancestors or from capparidaceous ancestors. Capparidean alliance is more tenable being based on the morphology of androecium and gynoecium and anatomy therein.
However, this family can be readily distinguished from Capparidaceae by having cruciform corolla, tetradynamous stamens, the absence of a gynophore, and the nature of the fruit. It is also related to Papaveraceae.
Economic Importance of Cruciferae (Brassicaceae):
There is considerable importance of the family for the production of fodder crops, weeds and ornamentals. The most important and edible food crops are cabbage, cauliflower, broccoli, brussel’s sprouts knol-kohl, turnip and radish. Economic weeds include mustards (Brassica), shepherd’s purse (Capsella) and pepper grass (Lepidium).
Oil is extracted from the mustard seeds and the oil-cake is used as manure and fodder. The table mustard is obtained from the seeds of black and white mustards. The ornamental plants are stocks (Matthiola), candytuft (Iberis), wallflower (Cheiranthus), etc.
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