Growth and Water Relations of Wheat Plants with Roots Split Between Soil and Nutrient Solution¹

Abstract

Soil matric potential controls plant growth. Yet it is difficult to determine the effect of soil matric potential, by itself, on plant water relationships and growth. One way to isolate matric potential is to split roots between soil and nutrient solution because the soil has a matric potential while the nutrient solution has a matric potential of zero. Therefore, in this study, leaf water potential, stomatal resistance, rate of water use, leaf area, plant height, and root length of winter wheat (Triticum aestivum L. em. Thell. cv. Osage), grown with and without wind, and with roots split between soil:soil, soil: nutrient solution (soln), and soln:soln were measured to determine the effect of soil matric potential on wheat water relationships and growth. During the first 16 days of the 38‐day experiment, the soil (Kirkland silt loam, Udertic Paleustoll) was well‐watered. Water was withheld from all soil treatments after the 16th day. Plants were grown with and without wind, and with and without soil drought, because, in the Great Plains, wind and drought, or a combination of the two, are the main causes of crop loss. Leaf water potential and stomatal resistance of plants with roots in soi1:soln were usually between those of plants with roots in soil:soin and soln:soln. Plants with all roots in nutrient solution had the highest leaf water potential and lowest stomatal resistance. Plants with all roots in well‐watered soil lost 2.5 times less water, but grew as well as plants with all roots in solution. Plants with roots split between solution and well‐watered soil lost the same total amount of water as plants with all roots in solution. But the plants with roots in soil:soln lost 7 and 11 times more water from the solution side than from the soil side of the split root containers for the wind and no‐wind treatments, respectively. Nonstressed plants (no wind, no drought) with roots split between soi1:soln were taller and had a larger leaf area than plants with roots all in soil or all in solution. The results showed that growth of wheat was increased if part of its root system was in media with zero matric potential (nutrient solution) and part in soil.

WATER RELATIONS OF WATER‐STRESSED, SPLIT‐ROOT C4 (SORGHUM BICOLOR; POACEAE) AND C3 (HELIANTHUS ANNUUS; ASTERACEAE) PLANTS

“…They have long been used to study the effect of stresses on plant growth, including the problem of water availability (Long, 1943). In such studies, roots of an individual plant are divided either vertically into layers in soil columns (Shalhevet and Bernstein, 1968;Gallardo, Turner, and Ludwig, 1994) or horizontally between containers with soil or solution in which matric or osmotic potentials are controlled (Slavikova, 1967;Lawlor, 1973;Erickson and Kirkham, 1979;Kirkham, 1980Kirkham, , 1983.…”

“…Most work comparing the water status of split-root plants has been done with C 3 plants (e.g., see Erickson and Kirkham [1979] or Kirkham [1980], who studied Triticum aestivum L., winter wheat). These studies showed that leafwater potential or stomatal conductance ofplants with half their roots under stressed conditions were only slightly lower than the water potentials or stomatal conductances of plants grown under nonstressed conditions.…”

“…Even though several studies have examined the plant water relations of split-root plants (Erickson and Kirkham, 1979;Kirkham, 1980Kirkham, , 1983, we know of no splitroot studies comparing the plant water relations ofC, and C 4 plants. (For us, the terms "plant water relations" or "plant water status" include the following measurements: water potential, osmotic potential, stomatal resistance, transpiration rate.)…”