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Abstract
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.
Abstract
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.
Abstract
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.
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. 5.3.1.9) 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.
An inexpensive system for maintaining desired water potentials throughout seed germination was developed. During hydration, a water reservoir at the base of inclined petri dishes allowed continual saturation of filter paper on which seeds were placed. During dehydration, seeds were exposed to equilibrium vapor pressures above saturated salt solutions. Constant temperature, necessary to prevent condensation of water vapor, was achieved via a small (0.2 A) fan that furnished and circulated heat throughout an insulated chamber in which salt solutions were placed. By operating the chamber above ambient laboratory temperature, interior cooling was not required. The system allowed manipulation of the rate, degree, and frequency of dehydration episodes to which germinating seeds were exposed.
Poa annua L. has long been a cultivated weed on golf courses. However, the recent development of improved cultivars of creeping bluegrass (Poa annua reptans Hausskn.) has generated an increasing interest in selection and breeding of this species. Inter-simple sequence repeat (ISSR) PCR is a relatively new method for genotype identification and measuring genetic diversity and was employed in this study for differentiating among creeping bluegrass genotypes. The objectives of this study were to test ISSR primers for production of polymorphic fragments and ascertain the applicability of ISSR PCR to distinguish closely related genotypes. Eight primers produced fragments, of which 77.3% were polymorphic, and primers UBC849, UBC850, and UMN001 produced over 75% of the total polymorphic fragments. These three primers had sufficient resolution to distinguish all but two of the diploid creeping bluegrass accessions. This method was a simple, fast, and relatively inexpensive method to produce useful DNA fragments in creeping bluegrass. It is a robust method for detecting polymorphic loci that can be used in the study of genetic relatedness, heritability, or linkage to important traits, development of linkage maps, and marker-assisted breeding.