Question

2a. Another avenue of research is on hydrotropism in plant roots given what you know about plant terminology & physiology what do you think this term means? How would plant root growth be impacted by hydrotropism?

2b. The hormone auxin is involved in many of the tropic responses, for example phototropism, that plants show & some have hypothesized that it might be involved in hydrotropism as well. What aspect of auxin physiology (production, function, mode of action… etc.) supports this hypothesis? (just think of one thing that you could use to argue for this idea!)

2c. What aspect of auxin physiology makes you suspect this might not be as important in hydrotropism as it is in phototropism? (now think of one thing that you could use to argue against the idea… then we go see what actually happens – science!)

Answer 1

2a. Another avenue of research is on hydrotropism in plant roots given what you know about plant terminology & physiology what do you think this term means?

Hydrotropism (hydro means "water; "tropism" means involuntary organism orientation involving turning or bending as a positive or negative response to a stimulus") is the growth response of a plant in which the growth direction is determined by a stimulus or gradient in the concentration of water. For example - a plant root which grows to a higher relative humidity level in humid air bending.

How would plant root growth be impacted by hydrotropism?

Plants perceive water in their environment in order to consume it for metabolic purposes. In plants, water can be detected and is absorbed mainly through the roots, primarily through young fine roots compared to mother roots or older fine roots. The path and rate of growth of these roots towards water are of interest as they affect water absorption capacity.
Receptor-like kinases (RLKs) tend to be responsible for this sensing of possible water gradients due to their appropriate position in root cap cell membranes, as well as their interactions and effects on a form of aquaporin water channel known as plasma membrane intrinsic protein (PIP). PIPs are also present in the cell membrane and tend to be involved in root hydraulic conductivity.
In this case, the signal for root growth differs in the soil environment of a plant with the water potential; the response is differential growth towards higher water potential. Plants sense potential gradients of water in their root cap and bend towards the signal in the mid-section of the root. In this way, plants can pinpoint where to go to get water.