The effect of root zone temperature on the growth and root anatomy of cucumber (Cucumis sativus L.)

The effect of the root temperature on the growth of cucumber plants was studied in a non recirculating hydroponic system. The plants were cultivated at root zone temperatures of 12 degrees C, 20 degrees C, 28 degrees C and 36 degrees C. Treatments were applied when seedlings had two fully expanded leaves. After 11 days the fresh and the dry weight of the roots, shoots and leaves were measured as well as the number of leaves, the leaf area, the root length and the root width. A root temperature of 28 degrees C gave the best performance in terms of dry matter production, leaf area and root length although there was no significant difference between the plants at 28 degrees C and 36 degrees C. There was a 88.9% reduction of the dry matter production at 12 degrees C, 26.8% at 20 degrees C and 5.0% at 36 degrees C compared to 28 degrees C treatment. Similarly there was a reduction of the leaf area which was 92.2%, 30% and 6.9% at 12 degrees C, 20 degrees C and 36 degrees C root temperature respectively. Root length followed a similar trend with 99.5%, 67.6% and 44.3% reduction at 12 degrees C, 20 degrees C and 36 degrees C solution temperatures respectively. Cross sections of the roots were examined under the scanning electron microscope. There was significant effect on the size and distribution of xylem vessels within the root. The area and frequency of xylem vessels was increased with increasing root temperature.