This page contains a Flash digital edition of a book.
65 Chapter 6 Anomalous Secondary Growth in Thickness Many of the plants possess normal stelar structure, but some


have unusual structure. These types are called anomalous or abnormal. The anomalies in them are due to various peculiarities as listed below.


1. Anomalous position of cambium. 2. Abnormal behaviour of normal cambium. 3. Accessary cambium formation and its activity. 4. Extrastelar cambium. 5. Interxylary phloem. 6. Scattered vascular bundles in dicotyledons. 7. Presence of exclusive phloem and xylem bundles. 8. Presence of medullary bundles. 9. Presence of cortical bundles. 10. Vascular bundles arranged in a ring in Monocots etc. Anomalous Sec. growth in Boerhaavia stem Boerhaavia (Family: Nyctaginaceae) shows anomalous


secondary growth in thickness because of its unusual primary structure and the presence of accessory cambium formation and its activity.


66


Primary structure The young stem of Boerhaavia shows normal structures of a


dicotyledonous stem, with a few exceptional characteristics. There is a single layer of epidermis with numerous hairs. It is followed by few layers of collenchyma. The cortex has few layers of parenchyma with chlorophyll bearing cells. The endodermis is not very distinct, it is usua-


Fig.3.10. Diagrammatic T.S. of young Boerhaavia stem


Fig.3.11. Boerhaavia stem T.S. Showing Sec. growth


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59