Starch gel electrophoresis was used to screen 10 enzyme systems for variation in fountain grass, Pennisetum alopecuroides (L.) Spreng. plants exhibiting four different growth habits: dwarf(d), mound(m), prostrate(p), and upright (u). Only phosphoglucoisomerase (PGI; E.C. 22.214.171.124) was found to be polymorphic at one locus, PGI-2, and was expressed as two alleles, which appeared to be associated with growth habit. The dwarf form expressed one slow band (SS), the mound and prostrate forms exhibited one fast band (FF), and the upright form carried triple bands indicating a heterodimer (FS). Hybrids between FF and SS parents were detected as triple bands (FS). Three generations of progeny resulting from 16 crosses and selfs of these growth habits all followed the expected segregation ratios for typical Mendelian inheritance of this isozyme.
Roots of container grown ‘Hetzi’ juniper developed cold hardiness to -10°C on December 2, 1963 in St. Paul, Minnesota as determined by controlled freezing tests. The temperature of container soil, under natural conditions, did not fall below 0° until after December 2. Once frozen, the soil temperature responded rapidly to falling ambient temperatures. Container soil temperatures of -10° occurred several times after December 2 resulting in root injury.
Tops developed cold hardiness from -15°C on September 11 to greater than -39° on December 2, 1963. No top injury occurred at any stage during the study. Winter injury common to container grown Hetzi Juniper in Minnesota is apparently root injury.
Maintenance of selected moisture and N levels in the soil throughout the fall did not significantly affect the rate of cold acclimation of container grown Juniperus chinensis cv. ‘Hetzi’ roots or tops. Two levels of soil N resulted in N of .79% ppm and 1.65% in the tops, and root N of .70% and 1.29% on December 2, 1963.
Plants receiving no N fertilization after September 2 decreased in total root N from 1.27% on September 11 to 0.70% on December 2. Tops decreased in total N from 1.62% to 0.84% during the same time period. Different soil moisture levels did not differentially affect the tissue moisture percentages, or cold acclimation.
Changes in total sugars, reducing sugars, total N and protein N showed little relationship to changes in cold acclimation. Root and top moisture percentages decreased during the fall, the rates closely paralleling the increase in cold acclimation. It is postulated that a decrease in the cellular moisture, resulted in increased concentration of cellular solutes and closer spatial arrangement of water binding substances. Cold acclimation may have resulted from the higher bound water/free water ratio.