Tropisms

Phototropism is the effect of light upon plant shoots. Plant shoots are likely to grow towards light and prosper but root growth and prosperity will be minimal. This would not occur without the hormone auxin. Stems are likely to bend and manuever towards a source of light.

Gravitropism is the effect that gravity has on a plant. The roots are expected to prosper and grow plentifully while the shoots do not.

Gravitropism is present in this photograph of he bulb because the shoot growth was and remained minimal for a number of days, but the roots never appeared to suffer from a shortage of growth.