Chemical Co-ord Flashcards
Define: Stimuli
Changes in the external or internal environment of an organism are called stimuli
What is a response?
The resulting action caused by a stimulus is called response
Fill in the blanks:
1. The main area of cell division in plants is _________.
2. ________ was the first phytohormone to be discovered.
3. The main auxin found in plants is _________.
- Meristems
- Auxins
- IAA (Indole 3 acetic acid)
G.R: Auxins are powerful growth stimulants
They are quite effective even in extremely low concentrations.
State the location of Auxins
Shoot tip, root tip, lateral meristems etc.
State the function of Auxins ( 4 m )
- Promote growth of shoot, root and fruits by cell elongation
- Delays leaf senescence.
- Promote growth of apical buts and inhibit growth of lateral buds.
- Induce fruit formation w/o fertilization in fruits like apples, tomatoes and bananas.
What is apical dominance?
Phenomenon of the suppression of growth of lateral buds by apical buds.
What is parthenocarpy
Development of fruit without fertilization
Give two examples of plants wherein Auxins induce rooting when cut
rose, bougainvillea
What is leaf senescence
The ageing / falling of leaves.
What are the different forms of Gibberellins? Which is the most studied form?
GA1,GA2,GA3.
Gibberellic acid (GA3) is the most studied.
State the location of Gibberellins.
Root tip, shoot tip, buds, seeds
What are the functions of Gibberellin?
- Promote growth of internodes by cell elongation
- Break seed dormancy and initiate germination.
- Capable of inducing parthenocarpy and promote fruit growth
- delay leaf senescence.
G.R: Gibberellins are used in horticulture and food industries.
They enhance longitudinal growth of internodes in dwarf plants and are used commercially to increase the length of grapes, elongate apples and improve their shape. It is also used to speed up malting process in the brewing industry.
State the location of production of cytokinins and where they are found in the plant.
Cytokinins are produced in the root tips.
They are found in germinating seeds, developing fruits and embryos.
State the functions of cytokinins.
- Stimulate plant growth by cell division even in non meristematic tissues
- In seeds, they cause expansion of cotyledons
- Break seed dormancy and promote germination
- Promote chlorophyll synthesis in chloroplasts and delay leaf senescence.
- inhibit apical dominance
______ is the only hormone which is a gas at ordinary temperature.
It was first found emanating from _______.
Ethylene. It’s site of synthesis and site of action are the same
Oranges.
What are the two plant processes caused by ethylene?
- Reduction in stem elongation
- Acceleration of senescence
State the functions of ethylene
- Ripening of fruits
- initiating germination in peanut seeds
- /sprouting of potato tuber
- Inducing flowering in mango
- promoting root growth and root hair formation.
G.R: Ethylene is most widely used plant hormone in agriculture
- Ripening of fruits
- initiating germination in peanut seeds
- /sprouting of potato tuber
- Inducing flowering in mango
_____ is a growth retarding hormone. State its location.
Abscisic acid.
It’s located in the chloroplasts of leaves
State the functions of ABA
- Acts as a growth inhibitor by slowing down plant metabolism
- Inhibits seed germination, induces seed dormancy to help the seed withstand desiccation
- Accelerates leaf senescence and abscission of buds, leaves and flowers and fruits.
G.R: ABA is also called the “stress hormone”
When there in insufficient absorption of water by roots, ABA stimulates closure of stomata to prevent excessive transpiration and thereby increasing tolerance of a plant to unfavourable conditions.
Define : Tropic movements
The movement of the plant part either towards or away from the direction of the stimulus
