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We hypothesize that drought-avoidance in Gutierrezia sarothrae populations is characterized by well-developed lateral roots. Root growth and hydraulic conductance were studied in four populations of Gutierrezia sarothrae. Seedlings from a Malta, Idaho (ID) seed source had four times higher root/shoot ratio (P<0.05), but only 17% hydraulic conductance of those from Tahoka, Texas (TA) seed source. Consequently, transpiration surface area of the ID seedlings was 17% that of the TA seedlings. There was no difference in total root length between the seedlings, but hydraulic conductance per unit root length was 3.8 fold greater (P<0.05) in the TA seedlings, which was accompanied by a lower specific lateral root length...
Pressure-volume analyses were done on a half-shrub broom snakeweed (Gutierrezia sarothrae) subjected to different soil water regimes under pot- and field-grown conditions. Under pot and field conditions, water deficit decreased water and osmotic potentials. In the severely droughted pot-grown, osmotic potential at full turgor (?100) decreased by 0.44 MPa due to reduced symplastic volume, the result of a decreased leaf turgid to dry weight (TW/DW) ratio. A reduction of 0.86 MPa in ?100 was observed in the field-grown plants subjected to the first drought cycle, but increased cell wall elasticity occurred in the second drought cycle. The lowered ?100 was attributed to osmotic adjustment and reduced symplastic volume....
Seeds from northern (Idaho) and southern (New Mexico and Texas) populations 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 into the lower pots for 4 weeks through punctures in the bottoms of the upper pots. Soil water extraction from four different depths was measured using time domain reflectometry (TDR) 2 weeks after roots had begun to grow into the lower pots. The two New Mexico populations (Jornada and Mountainair) and a population from Plains, Texas extracted more water from deeper (greater-or-equal,...