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Vascular Cambium and annual rings and secondarygrowth.pptx

Vascular cambium and cambium ring

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IN THE NAME OF ALLAH, THE MOST MERCIFUL THE MOST GRACIOUS
VASCULAR CAMBIUM
Vascular cambium secondary vascular tissues, xylem phloem vascular cambium cork cambium thickening Two lateral meristems in older stems and roots of woody plants produce secondary growth that results in an increase in diameter (whereas apical meristems result in an increase in length). Lateral meristems Cork cambium periderm (continually replaces the epidermis), bark tissue secondary xylem secondary phloem Bark secondary phloem
Vascular Cambium • In majority of Monocotyledons and Pteridophytes the primary plant body is structurally and functionally complete. In most Dicotyledons and Gymnosperms, primary growth is soon followed by secondary growth. • Secondary growth take place by the activity of cambium. The vascular cambium Is a lateral meristem. It is a continuous sheath of the meristematics cells. • The vascular cambium increase the diameter or girth of plant by secondary growth . • Cambium divide and produce new cells toward the inner as well as outer side. • In dicot stem the first procambium that develops from promeristem present in the form of patches in each vascular bundle between the primary phloem and primary xylem is called intrafascicular cambium or fascicular cambium. • The new cambium develop from the interfascicular region, some parenchymatous cells become meristematic and form the secondary cambium which is present between the two vascular bundles called interfascicular cambium . • The fascicular and interfascicular cambium joined together and form a complete ring of cambium cells known as cambial ring.
Origin of Vascular cambium
Structure of Vascular Cambium • The vascular cambium is made up of the two components- 1. Fusiform initial and 2. Ray initial 1. Fusiform initial: • These cells are spindle shaped and long with their pointed ends. It divide to form all cells of vertical system. The arrangement of the fusiforn initial is mainly two types in different plants. a. Storied or Stratified Cambium b. Non-Storied or Non- Stratified Cambium: a. Storied or Stratified Cambium: • In this case the fusiform initials are shorter and are arranged in horizontal rows so that their ends are approximately at the same level. This kind of cambium is found in Tamarix and Robinia etc. • According to Bailey the storied cambium have evolved by gradual reduction of the size of the cells and by longitudinal sliding growth.
Structure of Vascular Cambium b. Non-Storied or Non- Stratified Cambium: • In this case the fusiform initial are longer, partially overlap one another and are not arranged in horizontal rows. This kind of cambium occurs more commonly in plants 2. Ray initial: • The ray initial cells are smaller than the fusiform initial with their flattened axis. • The ray initials are isodiametric cells—about equal in all dimensions—and they produce the vascular rays, which constitute the horizontal system of secondary tissues; this horizontal system acts in the translocation and storage of food and water.
Fusiform initial and Ray initial
Storied and Non-Storied Cambium
Storied and Non-Storied Cambium
Types of cell division in vascular cambium • Additive division: it is periclinaldivision in which there is addition of xylem and phloem cells • Multiplicative division: this is anticlinal division in which multiplication of cambium initials take place to combat with the increasing girth
Types of cell division in vascular cambium
Function of Vascular Cambium • The main function of vascular cambium is the secondary growth of the stem ( increasing the girth of the stem ). • The cambium tissue divides continuously, adding new cells toward both side. • The cambium forms the cells outside, are differentiated into secondary phloem • While those formed toward inner side are differentiated into secondary xylem. • The ray initial gives rise to xylem and phloem rays. • During the division of cambium it gives an appearance of multilayered cambium known as cambial zone, but actually the cambium remain single layered.
During primary growth, the vascular bundles produce PRIMARY vascular tissue. These are the primary phloem and primary xylem. The fascicular cambium separates the two tissues. Remember: a fascicle is a vascular bundle Development of secondary vascular tissues in stems
Development commences within the fascicular cambium (between the primary phloem and primary xylem) The interfascicular regions begins to differentiate and a cambium originates here.
sieve plate sieve-tube member companion cell (living) one vessel member VESSEL TRACHEIDS pit in cell wall PHLOEM SIEVE TUBE Water conduction Sugar transport cytoplasm absent (cells dead at maturity Xylem Phloem Angiosperms Conifers The vascular cambium produces xylem and phloem
Seasonal activity of Vascular Cambium • Cambium of some plants remain active for their entire life time i.e cambial cell divides and resulting cells mature to form xylem and phloem element. • Not the all plant show the cambial activity. The seasonal activity usually found in the plants of the tropical region. • In autumn season cambium enters in dormant state and last for the end of summer. In spring season cambium again become active. • In autumn season (unfavorable) cambium is less active and produce the thick walled narrow, dark brown and much smaller xylem tissue (vessels are narrow) • In spring season (favorable) cambium become more active and produce large sized, thin walled and light color xylem element (vessels are large) which conduct more water than those produce in unfavorable conditions.
Seasonal activity of Vascular Cambium
Cambium and secondary xylem of a conifer Cambium Ray initials Late wood Early wood Rays Tracheids with bordered pits Cambium and secondary xylem of a conifer Direction of growth Recall how the cambium produces xylem cells. This drawing shows what those cells differentiate to.
vessel LATE WOOD EARLY WOOD toward stem surface Transverse section of Quercus rubra wood
Cell types in secondary xylem
Vascular Cambium and annual rings and secondarygrowth.pptx
Vascular Cambium and annual rings and secondarygrowth.pptx