Transport in Plants part 1 Chapter 7

Two systems: Xylem and Phloem Xylem carries mainly water and salts from roots to the parts of the plant above ground. Xylem sap can only move in one direction, from roots to leaves. Phloem carries products of photosynthesis from leaves to the rest of the plant. Phloem sap can move in any direction. Neither of these transport systems carry oxygen or carbon dioxide. O2 & CO2 move through diffusion.

Stem

Epidermis Epidermis is the outside layer of the plant that provides protection In stems and leaves its covered with a waxy cuticle that is waterproof.

Stomata Stomata are pores that allow entry of carbon dioxide In roots it may have root hairs that increase surface area. The opening is controlled by guard cells Guard cells take up water, bend, and open during day. (Turgid) At night they closed to prevent water loss

Parenchyma Parenchyma is made up of thin-walled cells used as packing tissue. Starch storage Structural support (turgid) Air sacs between cells allow gas exchange Water and salts are transported through the cells

Collenchyma Collenchyma is a modified form of parenchyma with extra cellulose at the corners to provide extra support. Midrib of leaf has collenchyma

Endodermis Endodermis is one cell thick Surrounds the vascular tissue in stems and roots

Mesophyll Mesophyll is made up of specialized parenchyma cells Specialized for photosynthesis Contain many chloroplast Two types Palisade: (column- shaped) closer to surface and contain more chloroplast Spongy

Pericycle Pericycle are cells one to several cells thick just inside the endodermis next to vascular tissue New roots grow from this layer

Vascular tissue Xylem contain tubes made from dead cells called “xylem vessel elements” The walls of the cells are reinforced with “lignin” a waterproof material Provides mechanical support In stems the xylem and phloem are found in what is called vascular bundles