Abnormal secondary growth

Botany systematics

1. Abnormal Secondary Growth Prepared By:Azka Javed

2. Secondary Growth An increase in plant girth due to vascular cambium or cork cambium is called secondary growth.

3. Secondary growth & lateral meristems

4. Anomalous Whereas the development, arrangement, activity of the vascular cambium in most woody dicotyledonous and Gymnospermous plants tends to be very similar, there are some alternatives which produce new secondary tissues that do not follow a normal pattern. As a result, the secondary plant structures that are formed are termed   anomalus . Most anomalous growth is associated with the formation of  multiple cambia .`

5. Abnormal Secondary growth Abnormal secondary growth  does not follow the pattern of a single vascular cambium a thick hair clit producing xylem to the inside and phloem to the outside. Some dicots have anomalous secondary growth, e.g. in  Bougainvillea  a series of cambia arise outside the oldest phloem.

6. Abnormal growth in monocot Most monocots either have no secondary growth or else anomalous secondary growth of some type;

7. Monocotyledons   Dracaena (the Dragon's blood tree) is the only monocot which has been shown to also have secondary growth in roots.

8. Anomalous secondary growth in dicot system Secondary growth in dicot systems characterized by the following;

9. By the formation of new cambium strips in the interfascicular region by the initiation of meristematic activity in the parenchymatous cells of primary medullar rays adjacent to fascicular cambium. These interfascicular cambium strips join with the fascicular cambium to from a complete ring of vascular cambium. Position of vascular cambium ring always lies between the primary xylem and phloem.

10. Cells of this cambium cut secondary xylem towards inner side and secondary phloem towards outer side. Normally single vascular cambium ring remains active and no extra cambium rings are formed except a ring of cork cambium which develops extra stellar .

11. Anomalous Secondary Growth : type of secondary growth which deviates from the normal type is regards as  abnormal  or  anomalous  secondary growth. In Dicot stem anomalous secondary growth occurs due to following reasons – Normal position of cambium with abnormal activity. Abnormal position of cambium with normal activity. Abnormal position of cambium with abnormal activity

12. Abnormal secondary growth in dicot stem Cross section of Boerhaavia stem, showing  successive rings of xylem and phloem

13. Abnormal secondary growth in different plants Beta vulgaris    root & stem . Beta  TS root

14. Abnormal secondary groth in plants Bougainvillea  is a member of the Nyctaginaceae and is an example of a dicotyledonous stem which displays anomalous secondary growth .  In this TS, near the centre of the stem, you will see some  primary vascular bundles  embedded in lignified pith parenchyma. Move the slide towards the outer regions, and you will notice that there has been fairly extensive production of secondary vascular tissue. Look for the  vascular cambium . Secondary phloem and secondary xylem lie on either side of it. The secondary xylem is composed of  tracheids ,   fibers  and  narrow-diameter vessels . Interspersed with the secondary xylem you will be able to see small pockets of phloem and what look like large- diameter of metaxylum .

15. Daucus  (carrot) root; Carrot root

16. Campsis   TS stem Bougainvillea

17.       6.  Serjania  stem                                                    

18. THANK YOU