SHOOT GROWTH, ROOT LENGTH DENSITY, AND WATER-USE OF BARLEY GROWN AT DIFFERENT SOIL TEMPERATURES

Temperatures considered optimum for root growth only occur near the soil surface in interior Alaska, and current literature inadequately describes low soil temperature (i.e. 5-degrees-C) effects on plant development. This study determined shoot and root characteristics of barley (Hordeum vulgare L.) when grown at varying root zone temperatures (RZT). Leaf area, number of leaves and stems, and aerial and root biomass were assessed at heading of barley grown in pots in a glasshouse at RZT of 5, 10, and 15-degrees-C. Plant stage and height were recorded twice weekly. Pots were sectioned at 5 and 10 cm below the soil surface to obtain root lengths and dry weights. Three replications of the experiment used sand as the soil media, a fourth replication used a soil/peat mixture. Plant water use was determined by subtracting the amount of water leached through pots from that added. Plants grown at 5-degrees-C RZT had a 30% slower leaf appearance rate, 50% fewer stems and leaves, and 70% less leaf area than grown at 15-degrees-C. Root length density increased with increasing RZT. Water use and water-use efficiency were least at 5-degrees-C RZT. Greater specific leaf weights at 5-degrees-C RZT indicated greater photosynthetic efficiency, but reduced water uptake resulted in less dry matter production than at 15-degrees-C RZT.