Growth and phosphorus, zinc, and manganese content of tomato, muskmelon, and honey locust at high root-zone temperatures

Horticultural species vary in growth response to root-zone temperature (RZT) that exceed 30 degrees C, but little is known about the effects of RZT on nutrient absorption. We determined the amount of phosphorus (P), zinc (Zn), and manganese (Mn) in plants of tomato (Lycopersicon esculentum Mill. 'Jet Star'), muskmelon (Cucumis melo L. 'Gold Star'), and thornless honey locust (Gleditsia triacanthos L. var. inermis 'Willd) grown in an Hoagland No. 1 nutrient solution that was held at 24 degrees, 27 degrees, 30 degrees, 33 degrees, and 36 degrees C RZT. Tomato dry mass and P and Mn contents were highest at 27 degrees C RZT, but tomato Zn content did not show a response to RZT. Muskmelon dry mass and P, Zn, and Mn contents, however, were highest at 36 degrees C. Honey locust dry mass and P and Zn contents did not vary with RZT, but honey locust Mn content decreased linearly with increasing RZT. Growth and P, Zn, and Mn absorption by muskanelon were increased by continuous exposure to RZT > 30 degrees C, whereas honey locust growth and P, Zn, and Mn acquisition were not changed by exposure to RZT > 30 degrees C. Growth and P, Zn, and Mn absorption by tomato, however, were decreased by continuous exposure to RZT > 30 degrees C.