Transports In Plants Flashcards
Transport in Plants
Need for a transport system: Large multicellular plants have a small SA:V ratio and large size; diffusion is not sufficient. Every cell needs a regular supply of O2, water, nutrients and minerals.
Plants are not very active, so their demand for oxygen is low – can be met by diffusion. But, demand for water and sugars is high – transport system needed to meet metabolic demands.
Distribution of vascular tissue:
Dicotyledonous plants: Plants with branching pattern of veins in the leaf (flowering plants without woody stem) – these plants have the following distributions of tissues.
Vascular tissue is distributed in vascular bundles containing the xylem and phloem as well as other types of tissue called parenchyma, collenchyma and sclerenchyma – that give strength and support.
Root:
Central core of xylem (X-shaped), phloem in corners – provides strength to withstand pushing through the soil
Endodermis surrounds vascular bundles, allows water to get into the xylem vessels.
Just inside the endodermis is a layer of meristem cells (cells that remain able to divide) called the pericycle.
Surrounding the epidermis is the cortex (parenchyma).
Stem:
Vascular bundles near outer edges of stem to provide strength and flexibility to withstand and reduce the bending forces.
Xylem is on inside and
the phloem on outside, between them is a layer of cambium – a layer of meristem cells that divide to produce new xylem and phloem.
Leaf:
Vascular bundles form the large central midrib and network of veins (support leaf). Xylem is at top, phloem at bottom.
Practical – Dissection of plants tissue:
The view the vascular tissue staining with a water-soluble stain (toluidine blue O) is required, the stem needs to take up stained water by transpiration and then cut longitudinally or transversely (cross- section) and examined with low power microscope. The plant is cut in thin cross-sections with a razor blade or scalpel, placed on slide, stained and covered with coverslip.
