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Texture The relative proportion of various sizes of mineral particles in a given soil or root medium. (Nelson, 2003)

Transpiration The loss of water from plant tissue in the form of vapor. (Nelson, 2003)

Tropism A growth response or bending toward or away from a stimulus. Geotropism is in response to gravity; roots grow toward, and shoots away from, the center of the earth's gravity. Phototropism is in response to light;shoots tend to grow towards the light. (Nelson, 2003)

Trough culture A closed system for growing pot plants in which a single row of pots is placed in a watertight trough arranged on a slight incline. Nutrient solution is pumped to the high end of the trough. It flows by gravity around the bases of the pots to the low end where it is channeled to a holding tank. Solution is drawn into the root medium by capillarity. The solution is reused each time the crop requires watering. (Nelson, 2003)

Truss A compound component of the greenhouse frame spanning the width of the greenhouse and consisting of rafters, chords, and struts that are welded or bolted together. (Nelson, 2003)