a temperature threshold is reached. This threshold is dependent on the thermal gradient, with the threshold being colder with smaller gradients. For example, a gradient of 4.2 C per cm had a threshold value of 30 C while a gradient of 0.5 C per cm had a threshold value of 24 C. It is thought that this lack of thermotropic response is due to the lack of sufficient stimuli to induce root curvature. Negative thermotropic behavior was recorded and was shown to occur at higher temperature, but the conditions to establish such behavior is less defined. Within the same experiment, roots were capable of undergoing positive thermotropism away from gravitational force. The inhibition of normal gravitropic curvature was seen when temperatures were 18 C and lower, with stronger curvature away from gravity seen with lower temperature. This overriding behavior indicates integration of the plant's gravitropic and thermotropic system and suggests that the sensory systems are an interconnected network of responses rather than separate stimulation response pathways. Thermotropism's relation with Heliotropism Para-heliotropic movements in the Phaseolus genus (beans) coincided with regulating leaf temperatures to improve photosynthesis efficiency and heat avoidance in hot, sunny, and arid environments. These movements worked to avoid photo-inhibition and keep leaf temperature lower than the air temperature. In sunflowers, we find a different relation involving floral warming. The floral heads of these plants follow the sun from east to west causing increased solar irradiation heating the plant. This resulted in more pollinators being attracted. A study showed this by forcing some floral heads to the west leaving other floral heads to warm illustrating varied pollinator choice. Though these findings are in correlation with heliotropisms, these heat avoidance and acquisition strategies are entwined with thermotropism as well. With further research, more examples can be found that can definitively detail the thermotropic role in heat avoidance and acquisition. References External links Why Do Rhododendron Leaves Curl? Tropism