Search Results
You are looking at 1 - 10 of 12 items for :
- Author or Editor: Janice Coons x
- HortScience x
The environment that seeds experience during development, storage, and planting significantly affects seed vigor. Yet, relatively few studies have focused on how environment during seed development affects seed vigor. Our objective was to compare vigor of seeds developed in summer vs. winter. Lettuce (Lactuca sativa L.) seeds from six cultivars were developed in summer and winter at Yuma, Ariz. Seed vigor of these seedlots was compared using field plantings and growth chambers (at 20, 25, 30, and 35C). Seed vigor was greater for seed produced during summer than for that produced during winter, based on greater field emergence, higher germination percentages, and longer roots. These seedlot differences in vigor were greatest at 35C. Another way to estimate seed vigor is by ion leakage from seeds. Fewer ions leaked from seeds produced in summer than from those produced in winter. Thus, lettuce seed is more vigorous when produced in summer than in winter, and ion leakage is a good indicator of that vigor.
Routine methods of teaching often do not challenge a student's ability to think creatively and independently. In many horticulture classes the emphasis is on learning of facts, principles, and techniques, rather than the consideration of controversial issues such as chemical usage. I have used student debates as a tool to discuss various horticultural issues which are controversial. Possible debate topics, methods for the presentation of the debates, and ways to evaluate the debates will be presented. The use of debates in horticulture classes will be considered from the perspective of both students and the instructor. Both strengths and weaknesses of student debates as a learning experience in horticulture classrooms will be presented.
Navy (Phaseolus vulgaris L.) and tepary (P. acutifolius Gray) beans were grown hydroponically in a growth chamber with no NaCl or -0.25 MPa NaCl for 9 days beginning 22 days after planting. Chloride and sodium distribution in leaves and roots as well as percent ion leakage as an indication of membrane integrity in leaves were determined. Chloride and sodium levels in NaCl treated plants were significantly higher than in controls. Chloride distribution was not significantly different between plant parts or between plant species. Sodium distribution was significantly different between roots of the two species, but not between leaves of the two species. The navy root tissues contained twice as much sodium as the leaves, whereas, in tepary sodium levels were similar in roots and leaves. Percent ion leakage showed no notable trends relative to plant species or to NaCl treatments, but a significant difference was observed between younger and older leaves on the same plant.
Acceptance of supersweet types of corn is hindered due to reduced field emergence in cold soils. Reduced emergence is related to seed endosperm composition and imbibitional leaching of seed components. Seeds of two supersweet cultivars (Illini Gold and Honey'n'Pearl) with shrunken-2 endosperm were examined for differences in percent germination and days to 25% germination at 10, 15, and 20 C. Seed leachate from seeds imbibed at 10, 15, and 20 C was analyzed for electrical conductivity, sugars, and amino acids. Germination percentages were higher for `Illini Gold' than for `Honey'n'Pearl' at all temperatures, and higher at 20 than 10 C for both cultivars. `Illini Gold' germinated sooner than `Honey'n'Pearl' at all temperatures. Electrical conductivity was higher for `Honey'n'Pearl' than `Illini Gold', and higher at 20 than 10 C for both cultivars. At all temperatures, sugars and amino acids in seed leachate were higher for `Honey'n'Pearl' that for `Illini Gold', but no significant temperature effects were observed. Imbibitional leakage of ions, sugars, and amino acids was more dependent upon cultivar than temperature.
Five supersweet cultivars of corn (Zea mays L. var. rugosa) were planted in fields and growth chambers to compare potassium effects on seedling development at low temperatures. In fields, seeds were planted at Urbana, IL, in 1991 when soil temperatures were 15C(April) and 23C(June). Potassium chloride(KCl) was banded at 0, 45 or 90 kg KCl/ha. After 32 days `Illini Gold', `Florida Staysweet', and `Crisp'n`Sweet' were more developed than `Honey'n`Pearl' and `How Sweet It Is' as indicated by emergence, height, leaf area and number, and weight in April. However for June, cultivar differences were observed only for emergence. KCl had no effect on any cultivars. In chambers, seeds were planted in trays(6×22×30 cm) of vermiculite mixed with 0, 5 or 10 g KCl/tray at 17 and 26C. After 15 days, cultivar responses at both temperatures were similar to those at the April field planting except at 26C where none differed for emergence. KCl only affected seedlings at 26C when 10 g/tray slowed development. Thus more differences were found between cultivars at lower than higher temperatures, and potassium did not improve seedling development at low temperatures.
Lettuce (Lactuca sativa L.) seed germination is inhibited at temperature higher than 25-30C. The extent of this inhibition varies between seed lots. Our objective was to determine how the season during which seed develops affects the ability of seeds to germinate and establish a stand at high temperatures. Lettuce seed, `Empire', was produced during 2 summers and 2 winters (1988 and 1989) in Yuma, AZ. These seeds were germinated at 20, 25, 30 or 35C in petri dishes or in growth pouches to determine percent germination or root lengths, respectively. Electrical conductivity of seed leachates was measured. Field emergence of seeds was tested with early fall plantings in Yuma, AZ. Percent seed germination was greater and root lengths were longer for the seeds produced in summer than in winter. Conductivity will be correlated with relative tolerance to high temperatures of the different seed lots. In the field, percent emergence of seed lots from summer and winter averaged 60% and 38%, respectively.
Seeds of two tepary bean lines (Phaseolus acutifolius Gray var. latifolius) and one navy bean cultivar (P. vulgaris L. `Fleetwood') were tested with 0.0-, – 0.3-, –0.6-, -0.9-, -1.2-, or – 1.5-MPa NaCl solutions to determine their relative salt tolerance during germination and emergence. Developmental stage was not affected at – 0.3 MPa, but with salinities more negative than -0.9 MPa, `Fleetwood' developed more slowly than the tepary lines; no plants emerged at – 1.5 MPa. Teparies tended to maintain higher water and osmotic potentials than navy over the range of NaCl concentrations used, although turgor was similar for all three genotypes. Leaf area was reduced more in navy than in white tepary at – 0.6 and – 0.9 MPa. Dry weights of navy were higher than those of either tepary bean at all NaCl concentrations, although decreases at higher salinities relative to 0.0 MPa were greater for navy than for teparies. Root: shoot ratios were higher at – 0.3 MPa than at 0.0 MPa, but were lower at the higher NaCl concentrations for all three genotypes. Overall, tepary beans tolerated NaCl better than navy. The characteristic that best indicated differences in salt tolerance was developmental stage.
Lettuce (Lactuca sativa L.) seed germination is inhibited at temperature higher than 25-30C. The extent of this inhibition varies between seed lots. Our objective was to determine how the season during which seed develops affects the ability of seeds to germinate and establish a stand at high temperatures. Lettuce seed, `Empire', was produced during 2 summers and 2 winters (1988 and 1989) in Yuma, AZ. These seeds were germinated at 20, 25, 30 or 35C in petri dishes or in growth pouches to determine percent germination or root lengths, respectively. Electrical conductivity of seed leachates was measured. Field emergence of seeds was tested with early fall plantings in Yuma, AZ. Percent seed germination was greater and root lengths were longer for the seeds produced in summer than in winter. Conductivity will be correlated with relative tolerance to high temperatures of the different seed lots. In the field, percent emergence of seed lots from summer and winter averaged 60% and 38%, respectively.
Abstract
White and brown accessions of tepary bean (Phaseolus acutifolius Gray var. latifolius) and navy bean (Phaseolus vulgaris L. ‘Fleetwood’) were germinated at 0.0, −0.5, −1.0, −1.5, −2.0, and −2.5 MPa of NaCl at 25 or 35C for 9 days. Differences in germination percentages and rates between the two species were significant, especially at the higher salt concentrations. At 25C and salinities greater than or equal to − 2.0 MPa, tepary accessions had significantly higher percentage germination and germination rates than navy. At 35C this difference was noted at −1.5 MPa. The fresh weights of root plus hypocotyl appeared lower than controls at even the lowest concentration of salinity (− 0.5 MPa), suggesting that seeds germinated with NaCl did not produce vigorous seedlings. Of the three beans tested, the two tepary beans were more tolerant to NaCl than the navy bean, with the white tepary being most tolerant.
Effect of furrow and drip irrigation 1-, 2-, or 4-days after all plots had been watered 8-days before harvest, on postharvest quality, was studied two years. Years had no effect nor was fruit firmness affected by water method or timing. Regardless of method, water 4-days before harvest produced fruit with significantly the lowest % sol. solids (10.8% vs. 12.2%), the greatest vol. (16.1 vs. 15.1 cm3×102) and the greatest % moisture (88.5% vs. 87.4%) vs. no water after 8-days before harvest. Water 1- or 2-days before harvest produced fruit with variable quality differences vs. no water after 8-days. Drip watering 4-days before harvest vs. no water after 8-days, negatively affected sensory attributes with preference panelists rating lower for sweetness and overall fruit quality. Furrow watering produced fruit with inconclusive sensory ratings.