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| Parts of a Flower |
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| Calyx |
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| The Calyx forms the outermost whorl in the flower. Its component parts are the sepals. The sepals are generally green in colour. Sepals give protection to the inner parts of the flower when the flower is in bud condition. In some plants like Fuchsia and some Salvia species the calyx becomes brightly coloured and it is called petaloid. |
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| In Mussaenda, one of the sepals of the calyx becomes prominent, brightly coloured and bract like. |
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| The Calyx is described as polysepalous when, the sepals are free from each other e.g., Brassica and is called gamosepalous when the sepals are united e.g., Crotalaria. But in Sunflower and Tridax the sepals are reduced into hair like structures called pappus. |
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| fig. 27.50 Modification of calyx |
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| When the sepals fall off as soon as the flower opens, the calyx is said to be caducous e.g., Argemone. But if the sepals fall off at about the same time as the corolla, the calyx is called deciduous e.g., Mustard. The calyx is described as persistent, when the sepals remain without falling off and are found on the fruit. e.g. brinjal, tomato. |
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| In Hibiscus a whorl of bracteoles is attached to calyx cup and it is known as epicalyx. |
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| Corolla |
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| The corolla constitutes the second whorl of the flower. It is composed of petals. The petals are brightly coloured thus making the flowers conspicuous, showy and attractive. In many cases the petals are also scented. The corolla helps in attracting insects for pollination. |
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| In the corolla, the petals may be either free from one another or they may be united. In the former case the corolla is described as polypetalous, e.g., Crotalaria and in the latter, gamopetalous e.g., Nerium: In a gamopetalous corolla, the lower portion is called the corolla tube. The upper portion is often lobed, the number of lobes indicating the number of petals in the corolla. |
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| Depending on the shape several types of corolla are recognised. Some of them are as follows: |
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| a. Cruciform corolla: The corolla is polypetalous and the four petals are arranged in the form of a cross. e.g., Mustard, Radish. |
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| b. Papilionaceous corolla : This type of corolla is seen in the members of the family Papilionaceae. The corolla is partly polypetalous and consists of five unequal petals. The largest is called the standard or vexillum. It encloses two smaller lateral petals called the wings, (alae) which in turn enclose two still smaller petals called keel petals or carinae. The two keel petal unite along the lower side to form a boat shaped structure. e.g. Crotalaria, Pea, etc. |
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| Flowers with tubular corolla |
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| fig. 27.51 |
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| infundibuliform corolla |
| Flower with campanulate corolla |
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| fig. 27.52 :Types of Corolla |
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| c. Tubular corolla : The corolla is gamopetalous. All the petals fuse to form a cylindrical tube. e.g., disc florets of Sunflower, Ipomoea |
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| d. Infundibuliform corolla : The corolla is funnel shaped. The corolla tube gradually tapers down to a narrow base, e.g., Datura, Tobacco. |
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| e. Campanulate corolla : The corolla is gamopetalous and bell shaped, e.g., Pumpkin, Spathodea campanuleta. |
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| f. Bilabiate corolla : Here the corolla is gamopetalous and two lipped. Generally the upper lip is narrow and the lower lip is broad. e.g., Ocimum, Leucas. |
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| g. Rotate corolla : This is a wheel-shaped corolla with the petals united into a tube below and their free ends are placed at right angles to the fuse. e.g., Vinca rosea. |
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| In some flowers like Nerium, a number of outgrowths arise from the throat of the corolla tube. They form the corona. |
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| When calyx and corolla are not distinguished, the whorl is called perianth and the components are called tepals. |
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| Aestivation : The sepals and petals are arranged in different ways in a compact manner when the flower is in the bud condition. This arrangement of the petals and sepals on the thalamus in the bud is called aestivation. The following types are commonly met with : |
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| a) Open : The margins of sepals or petals do not even touch each other e.g., corolla in Brassica. |
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| b) Valvate : Aestivation is said to be valvate, when the petals or the sepals just touch one another by the edges and do not overlap. e.g., Annona, Calotropis |
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| c) Twisted or Contorted : In this type, each petal or sepal overlaps on one side and is overlapped on the other side. Thus the parts overlap one another in a regular manner. e.g., Hibiscus. |
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| valvate : calotropis imbricate: caesalpinia |
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| quincunical: psidium twisted: hibiscus vexillary: crotalaria |
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| fig. 27.53 : Types of Aestivation a. valvate b. imbricate c. quincuncial d. twisted e. vexillary |
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| d) Imbricate : Here one petal or sepal is outside (external) and one is inside(internal) and remaining three petals are overlapping as in twisted aestivation. There are 3 types of imbricate aestivation. |
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| 1. Ascendingly imbricated: The posterior petal or sepal is internal and one is external, the remaining three are overlapping. e.g., Caesalpinia. |
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| 2. Descendingly imbricate (vexillary): This is seen in papilionaceous corolla e.g. Crotalaria. Here the standard petal (or vexilum) is outermost. This overlaps the two wingpetals (ale) which in turn overlap the two petals which are fused to form keel or carinate. |
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| 3. Quincunical : This is seen in members the family Myrtaceae such as Callistemon, Psidium, etc. Two petals are completely external (or outside) and two petals are completely internal (or inside) and the remaining one is partly external and partly internal. |
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| fig. 27.54 |
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