What is the role of the hormone auxin?
- stimulates cell elongation in stems and roots
- promotes apicial dominance
- stimulate root initiation in cuttings
- involved in phototropism and gravitropism
- delay fruit and leaf drop
Where are the main sites of production for auxins?
- the shoot tips (apical and root meristems)
- young leaves
- developing seeds
What are the main functions of cytokinins?
- stimulates cell division (cytokinesis)
- promote shoot growth and delay leaf deterioration (senescence)
- work with auxins to control root vs shoot balance
- promote bud formation
- promotes branching from axillary buds
Where are the main sites of production for cytokinins?
- roots (transported upwards via xylem)
- developing fruits
What are the main functions of Gibberellins?
- stimulate stem elongation and leaf expansion
- break seed domancy and trigger germination
- promote flowering in some plants
- stimular fruit growth
- controls height of the plant
- increases cell wall flexibility
Where are the main sites of production for Gibberellins?
- young leaves
- seeds
- root and shoot meristem
What are the main functions of Abscisic Acid?
- induces stomatal closure in water stress
- maintains seed dormancy
- counteracts grwoth hormones
- triggers leaf senescence (deterioration)
- increases elongation and reduces root branching
- acts against ethylene to block cell death
- detects water avaliable
Where is the main site of production for Abscisic acid?
- root cap
- developing seeds
What are the main functions for Ethylene?
- promotes fruit ripening
- stimulates apoptosis
- inhibits stema nd root elongation
Where are the sites of production for Ethylene?
- elongating root and shoot regions
What are the functions of shoot apical meristems?
- cell division for shoot elongation (adds cells upards, increasing the height of the plant)
- formation of leaves and buds which produces axillary buds
- intiation of reproductive organs
- hormone poduction as it produces auxin which maintains apical dominance
What is apical dominance?
the process by which the plants main stem remains the tallest by proritising the upward grwoth and preventing the side branches from developing too quickly
What does pruning do?
eliminates the source of auxin by removing the apical bud, which causes the plant to lose its apical dominance
What are axillary buds?
embryonic shoots located between a leaf and the stem that can grow into branches or flowers
What are the three functions of leaves?
- Photosynthesis — process of converting sunlight, water and carbon dioxide into glucose and oxygen
- Gas exchange through tiny pores called the stomata
- Transpiration — the release of excess water vapour to cool the plant and circulate water
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What does it mean when we say plants respond to their environment?
Plants adjust growth, development, and behaviour in reaction to environmental stimuli like light, gravity, water, and touch.
What is phototropism?
Growth response to light direction.
Which part of the plant shows positive phototropism?
Shoots — they bend toward light.
Which part of the plant shows negative phototropism?
Roots — they may grow away from light.
What hormone controls phototropism?
Auxin — it accumulates on the shaded side of the shoot, causing it to bend toward light.
Why is phototropism important?
It maximises light absorption for photosynthesis.
What is gravitropism (geotropism)?
Growth response to gravity.
How do roots and shoots respond to gravity?
Roots show positive gravitropism (grow downward); shoots show negative gravitropism (grow upward).
