outer and inner sides of xylem Example: Cucurbitaceae Cambium is absent between xylem and phloem. Stems of Monocots) Cambium is present between xylem and phloem. (Stems of Dicots and Gymnosperms) Xylem lies in the centre with phloem surrounding it. Example: Ferns (Polypodium) dicots and aquatic angiosperms Phloem lies in the centre with xylem surrounding it.
Example: Dragon plant- Dracena and Yucca Amphivasal/Leptocentric Closed Amphicribral/Hadrocentric Open Collateral Bicollateral Radial Conjoint Concentric Types of vascular Bundles Cortex Cortex consists of only parenchyma cells. These cells are loosely arranged with intercellular spaces to make gaseous exchange easier. These cells may store food reserves. The cells are oval or rounded in shape.
Sometimes they are polygonal due to mutual pressure. Though chloroplasts are absent in the cortical cells, starch grain are stored in them. The cells also possess leucoplasts. The innermost layer of the cortex is endodermis.
Endodermis is made up of single layer of barrel shaped parenchymatous cells. Stele is completely surrounded by endodermis. The radial and the inner tangential walls of endodermal cells are thickened with suberin and lignin. This thickening was first noted by Robert Casparay in .
So these thickenings are called casparian strips. But these casparian . Comparison of Primary Structure – Dicot and Monocot Root, Stem and Leaf Primary Structure of Dicot Root – Bean Root The transverse section of the dicot root (Bean) shows the following plan of arrangement of tissues from the periphery to the centre. Piliferous Layer or Epiblema The outermost layer of the root is called piliferous layer or epiblema.
It is made up of single layer of parenchyma cells which are arranged compactly without intercellular spaces. It is devoid of epidermal pores and cuticle. It possesses root hairs which are single celled. It absorbs water and mineral salts from the soil.
The chief function of piliferous layer is protection. g h i j k l Phloem Xylem Phloem Xylem Phloem Xylem Phloem Xylem a c e b d f Cambium Phloem Xylem Outer Cambium Outer Phloem Xylem Inner Phloem Inner Cambium Cambium Phloem Xylem Outer Cambium Outer