Tag: biology

When sprayed on flowers, any of the plant hormones gibberellin, auxin and cytokinin could stimulate the development of parthenocarpic fruit.

The critical photoperiod is the continuous duration of light which should not be exceeded in short day plants but should always be exceeded in long day plants. Here the critical night length for the long day plants are 9 hours which should more and the light phase should be smaller.

Gibberellins also promote bolting (internode elongation just prior to flowering) in beet, cabbages and many plants with rosette habit.

The chemicals releasing from a pre-synthetic neuron and interacting with specific receptors on post-synaptic neuron are called neurotransmitters. Cortisone is not a neurotransmitter.

Calcium carbide is used for ripening fruit artificially in some countries. When calcium carbide comes in contact with moisture, it produces acetylene gas, which is quite similar in reaction to the natural ripening agent ethylene.

Genes are the chromosomal part that carries genetic information from one generation to another. Each gene has a pair of two contrasting alleles which is responsible for the effect of the gene in dominant and recessive traits. If seven characters of weight are there each will have two sites in the gene which shows recessive and dominant characters.

In 1838, German botanist, Matthias Schleiden found that all plant tissues are made up of cells which have been essentially similar structure. German zoologist, Theodor Schwann in 1839 working independently observed that animal cells do not have cell walls but are otherwise similar amongst themselves. He put forward cell hypothesis which states that bodies of animal and plants are made up of cells. Schleiden and Schwann in 1839 compared their findings and formulated cell theory.

• By carefully observing the process of cell division, Rudolph Virchow in 1858, argued that cells only arose from the division of pre-existing cells.