User:Sophieblaisdell/Hydrotropism

The mechanism of hydrotropism can also be explained by plant ‘hearing’. An experimental study discovered that the roots of the plant detect the location of water by sensing the vibrations produced by water movement. The resulting data supports that plants will grow towards these water-produced vibrations. However, it is also seen that plants grow toward other sources of sound in cases where there is no water actually present. These findings also raised the question of how plants distinguish the vibrations produced by water in comparison to other environmental factors, such as insects or wind. When exposed to varying sounds, there were statistically significant results that showed an attractive response (roots grow toward) to water or sounds mimicking water, and an avoidance response (roots grow away from source)  (p-value<0.002). In summary, this research showed that pea plants do, in fact, respond to acoustic frequencies.

Recent research has found the significant involvement of auxin, cytokinin, ABA, and MIZ1 in hydrotropic processes. ABA treatment, in addition to blue light irradiation, and stressful environment conditions, increase MIZ1 expression in plants. Arabidopsis plants are dependent on MZ1 for displaying hydrotropic behavior in response to water gradients. The originating environment of a plant dictates the degree of hydrotropic behavior that they display; in dry regions plants exhibit more hydrotropic activity, and in wet regions they display less. Asymmetrical distribution of cytokinin in Arabidopsis roots has reportedly led to higher cell production, and thus increased root growth, in response to lower water potential. The importance of auxin transport for pea plant hydrotropism and gravitropism was proven in experiments that used a multitude of auxin inhibitors.

It has been hypothesized that ABA modulated by hydrotropism has an effect on auxin. ABA helps dictate which side of the root grows at a faster rate, and thus which direction the root will grow. In gravitropism, the gradient between cytosolic and apoplastic calcium levels plays a large role in initiating a physiological response in other tropisms, and it is hypothesized that a similar process occurs in hydrotropism. Calcium, auxin and ABA are all proposed signals for the initiation of hydrotropic root growth behavior.

Other stimuli such as gravity, pressure, and vibrations also help plants choreograph root growth towards water acquisition to adapt to varying amounts of. water in a plant’s soil environment for use in metabolism. For this reason, it would be beneficial for future research to be conducted on agravitropic mutant plants, such as the ageotropum mutant. Thus, far, these interactions between signals have not been studied in great depth, leaving potential for future research.