Light reduced final percentage of germination, maximum germination rate, and time to maximum germination rate of hulled creosotebush [Larrea tridentata (D.C.) Cov.] mericarps. The final percentage of germination declined at an osmotic stress greater than −0.4 MPa, but maximum germination rate increased at a stress greater than −0.6 MPa, and inflection time increased with increasing stress. Twice the recommended level of 3 fungicides tested had a negative impact on germination, and all fungicides delayed the time to maximum germination rate at all levels.
The effect of drought and salinity stress on emergence of six Guayule (Parthenium argentatum Gray) cultivars was investigated. Final percent emergence declined an average of 62% from optimum conditions to those of moderate stress. Whereas the effect of either stress was nearly equivalent on final percent emergence, drought had a slightly greater effect on maximum emergence rate and salinity a greater effect on inflection time (time to maximum emergence rate) in most cultivars. Cultivars had no effect on final percent emergence, but they did affect maximum emergence rate and inflection time. Germination of cultivar 11619 was more stress-tolerant than others, since it had a higher maximum emergence rate and lower inflection time under stress. Within cultivars, variability was high for final percent emergence and maximum emergence rate and low for inflection time.
The Arizona Certified Landscape Professional conducts educational programs and certification exams to increase the knowledge and skills of landscapers. To ensure that the program accurately reflects industry needs, we conducted a job analysis survey. Over 100 individuals in 48 landscape organizations responded. Two-thirds of the organizations were `for profit' as opposed to municipal parks departments, school districts, and resorts. Half the `for profit' organizations were small with gross receipts of less than $100,000 annually. Forty percent of the `for profit' organizations were devoted exclusively to landscape maintenance, 28 percent were restricted to installation, and the remainder did both installation and maintenance. Size and nature (`for profit' or `in house') of the organization had a significant impact on tasks and responsibilities of employees. These data will be used to modify the educational programs and certification exams to more closely resemble day-to-day activities among landscapers in Arizona.
Seed scarification and stratification (moist-prechilling) requirements of Mexican redbud [Cercis canadensis var. mexicana (Rose) M. Hopk.] and evergreen sumac (Rhus virens Gray) and the effects of temperature on final percent germination, maximum germination rate, and inflection time (time to maximum germination rate) for the above species plus seeds of mealy sage (Salvia farinacea Benth.) were investigated. Maximum predicted germination from a quadratic response surface was 95% after 62 minutes of concentrated sulfuric acid scarification plus 35 days of stratification for Mexican redbud, and 59% after 52 minutes of scarification plus 73 days of stratification for evergreen sumac. Mexican redbud germinated at 24 to 31C. Predicted optima for final percent germination, maximum germination rate, and inflection time were 100% at 28C, 30% germination per day at 31C, and 4 days at 29C, respectively. Evergreen sumac germinated at 21 to 31C. Final percent germination for this species declined with increasing temperature from a predicted maximum of 52% at 21C, whereas maximum germination rate increased with temperature to a predicted maximum of 69% germination per day at 31C. Inflection time was high at both extremes with a predicted minimum of 10 days at 25C. Mealy sage germinated at 21 to 34C. Predicted optima for final percent germination, maximum germination rate, and inflection time were 96% at 25C, 104% germination per day at 27C, and 3 days at 28C, respectively.
Root generation of guayule (Parthenium argentatum Gray) seedlings was determined by suspending 8, 10, and 12 week old plants in a bottom mist chamber. The number and length of new roots were significantly greater after 3, 6, 9, and 12 days for 12 week old as compared to 8 week old plants. The major difference between 10 and 12 week old plants was an increased root length of 0.44 and 1.03 cm, respectively, after 3 days.
Effect of cutting age (weeks after budbreak) and K-IBA concentration on percent rooting of Mexican redbud [Cercis canadensis var. mexicana (Rose) M. Hopkins], larchleaf goldenweed [Ericameria laricifolia (Gray) Shinners], littleleaf ash (Fraxinus greggii Gray), and evergreen sumac (Rhus virens Gray) were investigated. For cuttings treated with K-IBA, maximum predicted percent rooting from regression analysis was 88% for cuttings of Mexican redbud taken 4 weeks after budbreak and treated with 21 g·liter-1, 99% for larchleaf goldenweed taken 6 weeks after budbreak and treated with 16 g·liter-1, 86%, for littleleaf ash taken 16 weeks after budbreak and treated with 17 g·liter-1, and 24% for cuttings of evergreen sumac taken 16 weeks after budbreak and treated With 5 g·liter-1. Chemical names used: potassium salt of 1H-indole-3-butanoic acid (K-IBA).
The maximum predicted germination was 95% after 62 minutes scarification and 35 days stratification for mexican redbud (Cercis canadensis var. mexicana) and 59% after 52 minutes scarification and 73 days stratification for evergreen sumac (Rhus virens). Mexican redbud germination occurred from 24 to 31 C, evergreen sumac from 21 to 31 C, and mealy sage (Salvia farinacea) from 21 to 34 C. The maximum predicted final percent germination and the temperature at which it occurred for mexican redbud, evergreen sumac, and mealy sage was 104 at 27 C, 90 at 29 C, and 42 at 22 C, respectively. The maximum predicted maximum germination rate and the temperature at which it occurred for mexican redbud, evergreen sumac, and mealy sage was 30 at 31 C, 69 at 31 C, and 104 at 27 C, respectively. The minimum predicted inflection time and the temperature at which it occurred for mexican redbud, evergreen sumac, and mealy sage was 4 days at 28 C, 10 days at 25 C, and 3 days at 28 C, respectively.
‘Marfa Lace', ‘Alpine’, and ‘Tejas’ are new desert willow [Chilopsis linearis (Cav.) Sweet.] cultivars selected at the Texas A&M Research and Extension Center at El Paso and approved for release by the Texas Agricultural Experiment Station. Desert willow is a deciduous flowering shrub or tree native to the southwestern United States. The species exhibits considerable variability in floral color, but this generally has not been exploited through selection or breeding. The advantages of these new selections include large, semi-double flowers in ‘Marfa Lace’, large leaves and dark flowers in ‘Alpine’, and even larger flowers in ‘Tejas’. To my knowledge, no other semi-double desert willow has been released.
Apparent differences in flower and leaf size among Chilopsis linearis (Cav.) Sweet accessions were investigated. Corolla area ranged from 6.4 to 15.9 cm2, with significant differences among plants. Leaf width ranged from 5 to 17 mm, length from 80 to 206mm, and area from 1.7 to 12.7 cm2, with significant differences among plants for all three measurements. Leaf width accounted for 62.3% of the variability in area, length accounted for 17.7%, and width and length combined accounted for 89.7%. Width and length were not related.
The objective of this study was to compare the structure and efficacy in terms of retarding cuticular transpiration of leaf cuticles from eastern redbud (Cercis canadensis L.) and dull-leaf and glossy-leaf Mexican redbud [Cercis canadensis var. mexicana (Rose) M. Hopk.]. Leaves of Mexican redbud exhibited several xeromorphic characteristics compared to eastern redbud: a smaller, thicker leaf with thicker cuticles, more cuticular wax, a higher specific leaf mass, and greater hydrated water content on a leaf area basis. Mexican redbuds with a glossy leaf differed from those with a dull leaf only in a thicker adaxial cuticle lacking wax crystallite on the surface. Epicuticular wax crystallite were present on the abaxial surface of all leaves examined. Detached leaves of eastern redbud had a higher water loss rate than those of Mexican redbud only on a dry mass basis, not on a leaf area basis. There was no difference in the rate of water loss by detached leaves of glossy-leaf and dull-leaf Mexican redbuds after 4 hours.