What are Radial, Conjoint, Closed and Open Vascular bundles

ARRANGEMENTS IN VASCULAR BUNDLES




RADIAL:

When xylem and phloem in a vascular bundles are arranged in alternate manner on different radii then such arrangement is called Radial arrangement.

CONJOINT:

Xylem and Phloem when arranged on same radii in the vascular bundles is considered as Conjoint.

OPEN:

When xylem and phloem are seperated by vascular cambium. Such arrangement with cambium is considerd as Open vascular bundles as in Dicots.

CLOSED: 

Vascular cambium is absent in between the xylem and phloem such arrangement of vascular bundles with no cambium is called Closed vascular bundles as in Monocots.

Comments

Post a Comment

Popular posts from this blog

Anomalous secondary growth in Dracena(monocot) stem

Image
Normally secondary growth is absent in monocots. Monocots live for a short period of time and complete its life cycle. Example:jawar, maize, rice etc., But Dracena shows abnormal secondary growth being a monocot stem. Dracena belongs to Lilliaceae family. Formation of Periderm: During secondary growth few peripheral cells of general cortex becomes active and forms Meristem. This acts as Cork cambium or Phellogen. This cork cambium cuts off Cork tissue or Phellem towards outside and secondary cortex or phelloderm towards inside. By this periderm is formed. Formation of cambium: The inner peripheral cells of general cortex becomes meristemetic and forms cambium. Cambium forms parenchyma cells and xylem elements in its inner side. After a short period of time activity changes. Phloem is formed in such a way that phloem is surrounded by xylem. This type of vascular bundles are called Amphiphloic type. In which phloem is surrounded by xylem. ...
Read more..

Cyanobacteria : general characters, thallus organisation and species of cyanobacteria.

Cyanobacteria General characters: Also called as Blue-green algae. Found in water and other wet places. These are oxygenic photosynthetic, prokaryotic and gram negative bacteria. The outer layer of cell wall is made of lipo-polysaccharides and inner layer is having peptidoglycon. Ribosomes, thylakoids and phycobilosomes are present in cytoplasm. Ribosomes are 70s type, thylakoids contains phycobilosomes which has photosynthetic pigments like phycocyanin, phycoerythrin and small amount of protein. Reserve food material is cyanophycin granules, starch, glycogen, phosphate granules. Gas filled vacoules helps the bacteria to float on the surface of water.  Vegetative reproduction is by fission, fragmentation and by locomotion harmagonia. Asexual reproduction is byformation of akinites, endospores, exospores and nanocytes. Thallus organisation in cyanobacteria: Thallus organisation in the sense no differntiation of organism into different parts. It is in  thr...
Read more..

Metamorphosis,Retrogressive and progressive metamorphosis

Metamorphosis: The changes which takes place in the organisms from juveline stage to adult stage is called metamorphosis. The larval stage is quite different from adult stage. Retrogressive metamorphosis: In this process,larva posses advanced characters while the adult is retained or degenerated with primitive characters. Urochordata exhibits retrogressive metamorphosis where the larva shows advanced characters and adult posses degenerated characters. Progressive metamorphosis: In this process,the adult stage is advanced than larval stage and larva posses degenerated characters, whereas adult posses advanced characters.  It is seen in anurans of Amphibians.
Read more..