Exercise 9: The Stem

• Label the following.

  A) Terminal bud

  B) Node

  C) Node

  D) Internode

  E) Petriole

  
• Terminal region - simply the shoot's tip
• Leaf sheath - formed from either the leaf or its petiole surrounds the entire circumference of the stem
• Buds are undeveloped shoots found at the terminal and axil regions
• In the older part of the stem, leaf scars may mark the position of a previously attached leaf, and bundle scars mark the position of vascular tissue
• lenticels - pores where gas exchange occurs
• What is the modified stem part of the onion bulb?

  Underground

  
• What is the modified stem part of cladode of cactus?

  aerial

  
• What is the modified stem part of corms of taro?

  Underground

  
• What is the modified stem part of rhizomes of gingers?

  underground

  
• What is the modified stem part of runner or stolon of spiderwort or paspalum?

  Subaerial

  
• What is the modified stem part of tendrils of bitter melon or ivy ground?

  Aerial

  
• What is the modified stem part of thorns of bougainvillea or citrus?

  aerial

  
• What is the modified stem part of tubers of potatoes?

  Underground

  
• Stem vascular tissue takes in the form of vascular bundle scattered across the stem
• The vascular bundle in corn is surrounded by the bundle sheath, which is an enveloping tissue layer made from sclerenchyma or parenchyma cells
• In older corn stems, there may also be phloem fibers between the outermost side of the phloem and the bundle sheath
• The innermost protoxylem may collapse and turn into a lacuna
• The rest of the xylem is made up of xylem parenchyma
• Label the following found in the vascular bundle of a corn stem x.s.

  A) Xylem

  B) Sieve-tube elements

  C) companion cells

  D) Phloem

  E) Vessel elements

  
• Label the following found in a young stem x.s.

  A) Phloem

  B) Vascular cambium

  C) Xylem

  
• Label the parts of the periderm.

  A) Cork cambium

  B) Phellem

  C) Phelloderm

  
• Label the following structures found in vascular bundles of corn

  A) Lacuna

  B) Metaxylem

  C) Protoxylem

  D) Bundle sheath

  E) Phloem fibers

  F) Phloem

  
• Label the following found in a Pinus sp. stem x.s.

  A) Periderm

  B) secondary phloem

  C) Resin ducts

  D) secondary xylem

  E) lenticel

  F) vascular cambium

  G) xylem rays

  H) pith