U1T3 - Keywords (1) Flashcards
Plants
Photoperiod
Relative length of days and nights. Controls flowering.
SDPs
Short Day Plants. Flower when days shorter and nights longer. ‘Long Night Plants’ Can’t have much P730.
LDPs
Long Day Plants. Flower when days longer and nights shorter. ‘Short Night Plants’ Need plenty of P730.
Phytochrome
Pigment system which controls flowering in plants. Act as photoreceptor. Found in leaves. Exists in 2 forms (P660 + P730)
Red Light
Light of wavelength 660nm. Absorbed by P660. More of this during daylight so P730 accumulates.
Far Red Light
Light of wavelength 730nm. Absorbed by P730. Less during daylight so less P660 produced.
P730
Physiologically active form of phytochrome. Stimulates flowering in LDPs. Inhibits flowering in SDPs.
Hormone
Organic compound produced in 1 part of organism + transported to other parts to create a response.
Auxins
Involved in phototropism. Transported away from tip. Short distance movement relies on diffusion, long distance relies on phloem. Causes cell elongation, responsible for maintaining cell wall structure + can inhibit growth in high concs.
Gibberellins
Elongate internodal distance. Increases stem length. Can be used to promote growth in dwarf varieties of plants. Produced in leaves.
Internodal distance
Distance between leaves.
Cytokinins
Promote cell division in presence of auxin. Prevent senescence. Produced in meristematic tissues in division zone.
Senescence
Process of aging + breakdown of chlorophyll in older leaves.
Positive phototropism
Plants growing towards light to gain more light for photosynthesis.
Differential illumination
Light from one side only.
