Roots & Stems

• Stem is the above ground axis of a vascular plant. It doesn't include the leaf
• Shoot is the above ground portions of a vascular plant (leaves and stem)
• First land plants did not have true stems, roots or leaves
• Stems have meristems, primary growth and secondary growth (sometimes)
• Meristems are discrete regions of cell division (where stem grows from)
• Primary growth is growth in length/height, from an apical meristem.
• Secondary growth is in diameter from a lateral meristem
• Shoot apical meristem may produce: new stem tissues, leaf primordia, bud primordial, shoot apex protected by bud scales or young leaves
• shoots of most living plants are divided into modules (modular growth)
• module (phytomere) = axillary bud + internode + leaf