Bean seeds were planted and put on a sunny windowsill. As plants grew, their stems bent toward windo

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Bean seeds were planted and put on a sunny windowsill. As the plants grew, their stems bent toward the window. This bending was most likely caused by an

unequal distribution of auxin in the stem.

unequal distribution of a neurotransmitter in the stem.

equal distribution of auxin in the stem.

equal distribution of a neurotransmitter in the stem.

(AIIMS-2009)

Solution

The plant hormone, auxin, is more distributed on the side away from the unilateral illumination causing cells to grow faster in the darkerside, which in turn, causes the plant to bend toward the light. If the distribution were equal, the plant would grow just upwards. Neuro-transmitters are chemicals secreted by multicellular animals and are used in transmitting impulses in the nervous system.

Standard 12

Biology