向触性（英语：thigmotropism）是向性的一种，指生物的生长接触到物体时而影响的性质，常见于植物之中。在部分植物茎部的向触性是由一种由茎顶分泌的生长素（英语：auxin）造成的。接触到物体的一面生长素合成受阻，背光的一面因此会含有更多的生长素并向下运输。生长素一方面能够刺激细胞膜上的质子泵，质子由细胞浆流入细胞壁，造成细胞壁酸化。氢键和细胞壁多糖之间的键裂解，细胞壁松弛，细胞水势下降。细胞外水分流入造成细胞的伸长生长。另一方面，生长素会在基因水平上调节蛋白质合成，如周期蛋白，促进植物生长。

Thigmotropism is a directional growth movement of curvature which occurs in response to stimulus of contact. Thigmotropism is found in twiners and tendrils. After initial contact with support due to nutation, the tendril or twiner shows less growth in the region of contact and more growth on the other side. As a result they bend over the support. Later on bending or coiling may occur in lower parts of the tendril as well. Thigmotropism is a movement in which a plant moves or grows in response to touch or contact stimuli. The prefix thigmo- comes from the Greek for "touch" (θιγμός). Usually thigmotropism occurs when plants grow around a surface, such as a wall, pot, or trellis. Climbing plants, such as vines, develop tendrils that coil around supporting objects. Touched cells produce auxin and transport it to untouched cells. Some untouched cells will then elongate faster so cell growth bends around the object. Some seedlings also exhibit triple response, caused by pulses of ethylene which cause the stem to thicken (grow slower and stronger) and curve to start growing horizontally.