Abstract Detail

Physiology

Tzivion, Amit [1], Vandenbrink, Joshua [2], Kiss, John Z. [3].

The Phototropic Response of Roots and Shoots Under Differing Circadian Light Cycles.

Unlike animals, plants cannot flee from threats or stressors. Thus, plants have evolved the ability to respond to their environment in the form of tropisms. Tropisms are growth-mediated movements in response to an external stimulus. Phototropism is the ability to respond to light by growing either toward (positive) or away (negative) from the light source. Previous research in microgravity has shown that the shoots of plants tend to display negative phototropism in the presence of red light. Previous studies have shown that the roots of plants display positive phototropism upon exposure to red light. Exposure to blue light has been shown to have the opposite effect. In ground-based research, plants tend to display positive phototropism in the shoots in response to blue light and negative phototropism in the roots. The plant shade-avoidance response, which has been shown to be regulated by red light, is regulated by the plant’s circadian rhythm. Thus, we investigated the relationship between phototropic response and light cycles by disrupting the circadian rhythm of Arabidopsis seedlings by exposing the seedlings to differing light and dark cycles, followed by exposing the plants to 48 hours of either red or blue light. By exposing Arabidopsis seedlings to 90 hours of continuous white light prior to red light exposure, we saw negative phototropism displayed in both the shoots (-13.2°) of the plants and the roots (-13.5°). When exposing plants to a 12 hour light and 12 hour dark light cycle, we saw negative phototropism in the shoots (-19.5°) and in the roots (-64.0°). We observed the same results upon exposure to red light when alternating between 18 hour light and 6 hour dark cycles during germination: negative phototropism was seen in the majority of the shoots (-18.0°), while negative phototropism was seen in almost all of the roots (-38.5°). Although disrupting the circadian rhythm did not reverse the phototropic effects, we did see a trend in decreased phototropic response in plants whose circadian rhythm was disrupted. In the plants whose light cycles during germination exceeded 24 hours, phototropic effects both towards and away from the light source decreased on average. These studies also represent important experiments for our upcoming research project on the International Space Station in 2017.

1 - University of Mississippi, Department of Biology, University, MS, 38677, United States
2 - University of Mississippi, Biology, University, MS, 38677, USA
3 - University Of Mississippi, Graduate School, 100 Graduate House, University, MS, 38677, USA

Keywords:
Circadian
Phototropic
Arabidopsis.

Presentation Type: Poster
Session: P, Physiological Posters
Location: Exhibit Hall/Savannah International Trade and Convention Center
Date: Monday, August 1st, 2016
Time: 5:30 PM This poster will be presented at 6:15 pm. The Poster Session runs from 5:30 pm to 7:00 pm. Posters with odd poster numbers are presented at 5:30 pm, and posters with even poster numbers are presented at 6:15 pm.
Number: PPS004
Abstract ID:663
Candidate for Awards:None