EFFECT OF RESTRICTED WATERING ON SAP FLOW AND GROWTH IN CORN (ZEA-MAYS L)

The heat balance technique for measuring sap flow was used to determine how plant stress from watering various proportions of the root system in corn (Zea mays L.) affects sap flow and root and shoot growth. Sectional root-boxes were used to divide the root system into four equal compartments so that known proportions of the root system could be subjected to water stress. Results indicated that the root-box technique is useful in studying the effects of adverse growing conditions in corn. Treatments consisted of no watering and watering one, two, three, or four sections of the box. Sap flow was measured using gauges that worked on a heat balance principle, and aspects of root and shoot growth were also measured. With-holding water from two or more sections of the box for 26 d resulted in decreased sap flow and fresh and dry weight of stalks compared with plants where all four sections were watered (control). Plant height was lower in boxes where one or more sections were deprived of water compared with the control. Dry weight of roots was less when water was withheld from three or all sections of the roots, and fresh weight of roots was less when water was withheld from all four sections. Corn plants with even half the roots growing under stressed conditions resulted in decreased sap flow and shoot growth.