Search Results
Abstract
Treatment with 500 ppm ethylene for 24 hr or with 4000 ppm Ethrel (2-chloro-ethanephosphonic acid) dip for 30 sec resulted in ‘Anjou’ pears attaining full ripeness without a concomitant change in respiratory activity. A decrease in flesh firmness and increases in protein nitrogen and soluble pectin occurred, even though the fruit remained in the preclimacteric condition. This was shown by a positive response in rate of respiration to ethylene at the fully ripe stage. Continuous, 48- and 24-hr treatments resulted in comparable rates of ripening. However, while the continuous and 48-hr treatments induced the climacteric rise in respiration, the 24-hr exposure failed to do so. The effect of ethylene on respiration is independent from its effect on the initiation of ripening; a respiratory response probably requires a higher concentration or longer exposure to ethylene than does a ripening response.
Abstract
Single-node cuttings obtained from 2-month-old seedlings of pecan [Carya illinoinensis (Wang.) K. Koch] were induced to break buds and form multiple shoots in liquid, woody plant medium (WPM) and 2% glucose supplemented with 6-benzylamino purine (BA) at 3 mg/liter. In vitro-derived shoots soaked in 1-3 mg/liter indolebutyric acid (IBA) produced adventitious roots in vitro; when soaked for 8 days in 10 mg/liter IBA, they were rooted successfully in soil and acclimated to greenhouse conditions. Etiolation of stock plants did not improve shoot proliferation or rooting under in vitro culture.
Lack of effective weed control is the major limiting factor in strawberry production. With few herbicides labeled for use in this perennial crop, weeds are controlled using manual labor, cultivation, and one or two herbicide applications. However, these practices do not provide long-term, effective weed control, and weeds continue to be the number one reason why strawberry fields are removed from production due to a reduction in yield. The objective of this study was to evaluate weed control during strawberry plant establishment using woven woolen mats and spring-sown canola. The effects of these mulches on weed control and strawberry plant production were studied independently and in tandem. Weed and daughter plant counts were compared among treatments to test for differences. Wool mulch, both single- and two-ply, was an effective barrier to weeds within the strawberry rows. Planting canola between rows or broadcasting in combination with the wool mulch decreased the number of weeds when compared to other treatments. The four treatments that included wool had the highest number of rooted daughter plants when compared to all the other treatments except the weed-free plot. The canola treatments without wool mulch did not produce as many rooted daughter plants and were not statistically different from the weedy-check.
Abstract
Tassel date, silk date, plant height, ear height, shank length, husk extension, tip blanking, row number, ear length, and first ear weight were studied in a diallel involving 7 inbred sweet corn parents. Both general combining ability (GCA) and specific combining ability (SCA) were involved in the inheritance of all 10 characters. This was consistent for F1 crosses in 2 years and for F2 families. SCA variance (VSCA) was larger than GCA variance (VGCA) for ear length and first ear weight in the F1 and ratios of VSCA/VGCA for these characters were slightly larger than 1.0. VGCA was larger than VSCA all other characters in the F1. Ratios of VSCA/VGCA ranged from .05 for row no. to .57 for plant height.
Variance ratios for most characters decreased in the F2. The failure of some ratios to decrease in the F2 was attributed to either differential interactions of GCA and SCA with environment or inadequate sampling of F2 families. Genotype × year interactions influenced the expression of most characters. A greater portion of the genotype × year interaction was contained in estimates of SCA than in estimates of GCA. Heritability estimates from parent-progeny regression were generally larger than those from variance components, although these estimates were generally in close agreement.
Abstract
Root promotion and root inhibition were measured for geranium and poinsettia cuttings during and after treatment at medium temp of 5 to 35°C at 5°C increments for 1 to 5 days. Optimum root initiation and elongation temp from 1 day of treatment were 15 to 30°C with reduced root initiation after 5 and 35°C and inhibition of root elongation after 5, 10 and 35°C treatments. Medium treatments for 3 or 5 days at 25 and 30°C increased root initiation and elongation which continued at accelerated rates during a 5 day period following treatment. Medium temp 5, 10, 15, and 35°C for 3 or 5 days reduced root initiation and elongation during treatment, and inhibition continued after treatments of 5, 10, and 35°C. Roots became brown for both species during 35°C treatment, while roots at 25°C and below remained white. After treatment root tip vascular and cortical cells varied in size but were anatomically similar. Distances from the root tips to the 1st xylem element were largest at 25°C allowing more cortical cells in the meristematic region.
Abstract
Temperatures for several post-bloom periods were correlated with days from full bloom to ‘Bartlett’ pear maturity. Date of maturity based on pressure test showed a high negative correlation (r = -.88) with mean temp above 40°F for the 36 days following bloom. The peak thermal period occurred 26-30 days after bloom, with the highest correlation on the 28th day. Days to maturity had a higher correlation with accumulated mean temp above 45°F than with degree hr above 45°F for the same periods. Base temp of 38.5°F to 50°F gave r values greater than -.85 in this prediction method. Mean temp between 41.5°F and 68.5°F on the 28th day had a linear correlation r of -.71 with days to maturity. Equal temp increments were more effective at min levels than at max levels for accelerating maturity. The post-bloom thermal period affecting maturation coincides with the stage of cell division and most effective time for application of chemical thinning sprays.
Abstract
‘French’ prune (Prunus domestica L.) leaves on nonbearing trees and large scaffold limbs had greater percent dry matter and specific leaf weight than those from bearing ones early in the season. This difference disappeared as the season progressed. Much of the difference could be attributed to the greater accumulation of starch, which displaced water. The demand for photosynthates by the crop was also reflected by lower starch content in 1-year-old shoot, limb bark, and roots, but no difference in the soluble carbohydrate content nor in the ratio of sorbitol + sucrose/glucose + fructose was observed. Leaf K content was influenced by the crop but not Ca and Mg contents. Unlike K contents, Ca contents in fruiting spurs and 1-year-old shoots tended to be greater than those from nonbearing samples; no differences were noted in root samples. These data and those of other workers indicate that K deficiency in this cultivar stems from its strong K demand by the fruit and from the lack of carbohydrates being translocated to the roots, which in turn, limits growth and nutrient uptake, especially K, which is limiting in these soils.
Three systems of peach production have been established (Flore, et al., 1991, HortScience 26(6):747) utilizing three levels of chemical input: conventional input, moderate level, and low level. The moderate and low levels of chemical input use increasing degrees of IPM. In 1992, data were collected on yield, insect and disease impact on fruit quality, vegetative growth, nitrate and simazine levels in the soil, and insecticide residues in the fruit. The yield per tree was substantially higher in the conventional treatment but this effect could be attributed to an early spring frost, local topography, or the treatment system. The percentage of fruit free from insect and disease damage was highest in the conventional treatment (95.1%), but the low input had a relatively high percentage of fruit free of damage (79.6%). Shoot cold hardiness of one year old shoots was not affected by treatment. Bud survival after a spring frost was greater in the conventional orchards, but topography may have influenced this parameter. Nitrate levels 2 m in the soil and sim-azine residues in the A horizon were not affected by treatment. Lorsban®, Guthion®, and Asana® residues in fruit are currently being analyzed and will be discussed. Additional data collected in 1993 and future years will contribute more information on the use of the low and moderate chemical input treatments on peach production.