Anomalous forms of growth
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The document discusses anomalous forms of secondary growth in plants, focusing on two main types: abnormal growth from normal cambium in dicots and abnormal growth from abnormal cambium in monocots. It explains the processes involved in each type, detailing the variations in vascular tissue arrangement and the role of cambium during secondary growth. The document highlights specific examples, including the development of vascular bundles and the formation of cork cambium.
Anomalous forms of growth
- 1. Presentation topic Anomalous forms of growth Submitted To, sir Ghulam Sarwer Submatted By, Saba Muneer Roll num 05 Smester 5th Botany(eve) Department of life sciences IUB
- 2. Anomalous forms of growth Defination:- Alternative type of cambium show abnormal activity and produce alternative secondary bodies that differ from common type, their growth is called anomalous secondary growth.
- 3. Types of anomalous growth There is two types of anomalous secondary Growth; 1. Abnormal growth from normal cambium in dicot 2. Abnormal growth from abnormal cambium in monocot
- 4. 1. Abnormal secondary growth from normal cambium In this type; cambium of normal type is present and persist but by peculiarity or irregularity in its Activity develop vascular tissues of unusual arrangement.
- 5. 2 Abnormal secondary growth from abnormal cambium In this type; the normal cambium either does not develop. This abnormal cambium may either develop from cortex or pericycle and shows abnormal activity.
- 6. 1. Explanation of abnormal secondary growth from normal cambium In several dicots, a vascular cambium of the common type arises and produces ordinary secondry xylem and sec.phloem. After a short period;the cambium cells stop dividing and diffretiated into xylem. Oldest sec. phloem then become reactivated and diffrentiate into a new vascular cambium that acts just like first; producing ordinary xylem and phloem.
- 7. The second cambium arose in the outer-most phloem,the xylem it produces is located exterior to the phloem of the first cambium. From interior to the exterior; there is first xylem, first phloem, second xylem and second phloem. This type of secondary phloem, located between two bands of xylem is included phloem.
- 8. 2 Explanation of Abnormal secondary growth from abnormal cambium In monocotyledons normally the vascular bundles are closed. The cambium being absent the secondary growth is absent; but in some plants like Dracaena and Yucca secondary growth takes place. The young stem has typical structure i.e. epidermis is followed by sclerenchymatous hypodermis. A large number of closely arranged bundles are scattered in ground tissue.
- 9. One of the outer layers of cells from the ground tissue becomes meristematic and functions as cambium. The cambium formed in the region which has ceased elongating. The activity of this cambium is more on the inner side and very little on the outside where it forms only parenchyma. On the inner side it forms xylem and parenchyma in alternate patches. The inner parenchymatous cells are called conjunctive tissue. After a short while the activity of cambium on inner side changes and above the xylem it starts forming phloem and then again xylem.The xylem formed earlier has bigger vessels. Around each vascular bundle is developed sclerenchymatous sheath.
- 10. The cambium after sometime alters its activity and forms xylem on the inner side, at those places where it was previously forming the parenchyma and parenchyma in place of xylem. Similar to earlier case again by change in activity it forms a ring of vascular bundles. Activity of cambium goes on changing regularly and more rings of vascular bundles are formed. Cork cambium is formed below hypodermis and forms cork and cork cambium in normal fashion.