Cg. Wan et al., WATER ACQUISITION AND ROOTING CHARACTERISTICS IN NORTHERN AND SOUTHERN-POPULATIONS OF GUTIERREZIA-SAROTHRAE, Environmental and experimental botany, 35(1), 1995, pp. 1-7
Seeds from northern (Idaho) and southern (New Mexico and Texas) popula
tions of broom snakeweed (Gutierrezia sarothrae) were germinated in a
greenhouse and the seedlings grown in a soil mixture in 30-cm deep (19
-1) plastic pots for 50 days. The pots were then fastened onto the top
of similar pots and the seedling root systems were allowed to grow in
to the lower pots for 4 weeks through punctures in the bottoms of the
upper pots. Soil water extraction from four different depths was measu
red using time domain reflectometry (TDR) 2 weeks after roots had begu
n to grow into the lower pots. The two New Mexico populations (Jornada
and Mountainair) and a population from Plains, Texas extracted more w
ater from deeper (greater than or equal to 38 cm) soil layers than the
Idaho population (P < 0.05). Root length in the deeper soil layers (5
5-60 cm) was greater (P < 0.05) for the Jornada desert population than
for the Idaho and Mountainair populations. The Plains population had
shorter roots and extracted less water in the upper soil layers than t
he other populations (P < 0.05). Specific root length in the Idaho pop
ulation was at least 67% greater (P < 0.01) than those in southern pop
ulations, indicating smaller root diameters. The patterns of soil wate
r extraction and root penetration were correlated with the seasonal di
stribution of precipitation in the plants' natural habitats. The Idaho
seedlings had roots confined primarily to the topsoil to secure water
from spring precipitation. In contrast, some southern seedlings were
able to develop an extensive deep root system to avoid spring drought.