9.1 Transport Systems in Dicotyledonous Plants

• Why do plants need transport systems to suit their size?


  to move substances both up and down from the tip of the roots to the topmost leaves and stems
• What are dicotyledonous plants (dicots)?


  make seeds that contain 2 cotyledons
• What are cotyledons?


  organs that act as food stores for developing embryo plant and form first leaves when seed germinates
• What are woody dicots also known as?


  arborescent dicots
• What is the vascular system in plants?


  series of transport vessels running through the stem, roots and leaves
• In herbaceous dicots, what is the vascular system made up of?


  xylem and phloem
• What are vascular bundles?


  transport tissues arranged together in the leaves, stems and roots of herbaceous dicots
• The pattern of vascular tissue is easily recognised and is shown in transections
• Why do multicellular plants have transport systems?


  metabolic demands, size, surface area to volume ratio
• Why do plants need transport systems to suit their surface area to volume ratio?


  small surface area to volume ratio so can't rely on diffusion to supply their cells
• What are the 2 types of dicots?


  herbaceous and woody
• Features of herbaceous dicots?


  soft tissues, relatively short life cycle
• Features of woody dicots?


  hard lignified tissues, long life cycle
• Why do plants need transport systems to suit their metabolic demands?


  cells of green parts of plant photosynthesise but many parts don't so need oxygen and glucose transported to them + waste products of cell metabolism removed -> also hormones and mineral ions
• TS stem of young herbaceous plant

  A) epidermis

  B) cortex

  C) phloem

  D) xylem

  E) vascular bundle

  F) parenchyma

  G) (packing and supporting tissue)

  
• TS root of young herbaceous plant

  A) root hair

  B) exodermis

  C) epidermis

  D) endodermis

  E) xylem

  F) cortex

  G) phloem

  
• TS dicot leaf

  A) palisade mesophyll

  B) main photosynthetic tissue

  C) vascular bundle

  D) xylem

  E) phloem

  F) midrib leaf

  
• Describe vascular bundle arrangement in the stem


  around the edge to give strength and support
• Describe vascular bundle arrangement in the roots


  in the middle to help the plant withstand tugging strains as stems + leaves are blown in the wind
• Describe vascular bundle arrangement in leaf


  midrib of dicot is main vein carrying vascular tissue through organ - also helps support structure of leaf - small branching veins spread for transport and support
• Is xylem living or non-living?

  non-living
• What are the 2 main functions of xylem?


  transport of water and mineral ions, support
• What is the flow of materials in the xylem?


  up from the roots to the shoots and leaves
• Describe the structure of xylem cells


  long, hollow structures made by several columns of cells fusing together end to end
• What are the 2 tissues associated with xylem?


  parenchyma and tannin
• What does parenchyma do in the xylem?


  packs around the xylem, storing food and containing tannin deposits
• What is tannin?


  bitter astringent-tasting chemical that protects plant tissues from attack by herbivores
• What do lignified secondary walls do in xylem fibres?


  provide extra mechanical strength but do not transport water
• What are the different ways lignin can be laid down in the walls of xylem vessels?

  rings, spirals, relatively solid tubes with lots of small unlignified areas
• What are bordered pits?


  small unlignified areas
• What happens at bordered pits?


  water leaves the xylem and moves into other cells of the plant
• Where do the spirals of lignin run in the xylem?


  around the lumen of the xylem
• What does lignin do in xylem vessels?


  helps reinforce xylem vessels, so don't collapse under transpiration pull
• LS xylem vessel

  A) hollow tube

  B) (no cytoplasm)

  C) thick lignified wall

  D) non-lignified pit

  E) region where end cell wall has been lost

  
• TS xylem vessel

  A) lignified cell wall

  B) xylem parenchyma

  C) lumen of xylem vessel

  
• Spirals of lignin in xylem

  
• Is phloem living or non-living?

  living
• What does phloem transport?

  food in the form of organic solutes around the plant from the leaves where they are made by photosynthesis
• What does the phloem supply the cells with and why?

  sugars and amino acids needed for cellular respiration and for the synthesis of other useful molecules
• What is the flow of materials in the phloem?

  both up and down the plant