Hormon tumbuhan (Fitohormon) | Biology

Scientific concepts / nature phenomena presented

• Plant hormones (phytohormones): Internal factors that regulate plant growth.

Discovery / origin of the term

• Hormones are associated with a discoverer mentioned as Fritz W. (Wamer/Wolm… likely “Fritz Warmol / Fritz W. …”) in 1928.
• Etymology is given from Greek: hormolite, meaning “plant hormone activator.”

Seven types of phytohormones

Auxin

• Chemical description: an acetic acid compound with an indole group (and derivatives).
• Discovery context (as stated): first found at the tip of the coleoptile of Avena sativa sprouts.
• Phototropism (bending toward light)
  • Auxin is produced at the tip.
  • When exposed to sunlight, auxin changes to a compound that inhibits growth.
  • The side not exposed to light grows faster, causing the stem to bend toward light.
• Functions listed
  • Stimulates cell elongation
  • Stimulates flower and fruit formation
  • Stimulates elongation of the growing point
  • Affects stem bending
  • Stimulates formation of lateral roots
  • Aids differentiation processes

Gibberellin

• Origin / discovery context: first linked to the fungus _Gibberella fujikuroi_, a parasite on rice.
• Discovery (as stated): discovered by eight kurosawa in 1926 (name likely intended as E. Kurosawa).
• Functions listed
  • Stimulates cambium cell division
  • Promotes early flowering
  • Stimulates seedless fruit formation
  • Causes plants to grow rapidly, leading to giant size

Cytokinin

• Described as a group of similar compounds.
• Functions listed
  • Stimulates cell division
  • Delays shedding of leaves, flowers, and fruit
  • Influences growth of shoots and roots
  • Increases resistance to adverse conditions (low temperature, viral infection, radiation)
  • Inhibits leaf yellowing by maintaining balanced protein and chlorophyll content

Ethylene (gas)

• Described as a gaseous growth hormone.
• Functions listed
  • Helps break dormancy
  • Supports fruit ripening
  • Supports leaf “weathering” / senescence (leaf aging; phrased as “weathering on leaves”)
  • Supports flowering
  • Inhibits root elongation in some species
  • Stimulates germination and supports formation of root hairs

Abscisic acid (ABA)

• Described as inhibitory to growth in most cases.
• Functions listed
  • Reduces growth rate or stops cell division and elongation
  • Inhibits seed germination
  • Affects plant flowering
  • Extends dormancy of tubers
  • Induces shoot dormancy

Kalin (as written)

Likely intended to be “cytokinin” or another term; the subtitles suggest splits into types related to potassium.

• Described as affecting formation of organs.
• Types listed (by organ affected)
  • Rhizokalin → affects root formation
  • Kaulokalin → affects stem formation
  • Phylokalin → affects leaf formation
  • Antokalin → affects flower formation

Traumatic acid

• Associated with wound response and regrowth.
• Described phenomenon: if the plant is injured, it can be repaired again via restitution / regeneration.
• Connected to the presence of traumatic acid.

Researchers / sources featured (as named in the subtitles)

• Fritz Walmor UN (mentioned as discovering phytohormones; year stated: 1928)
• (E.) Kurosawa (subtitles: “eight kurosawa,” discovery year 1926)
• Fungus species mentioned: _Gibberella fujikuroi_
• Plant species mentioned: _Avena sativa_ (coleoptile used in the auxin discovery description)