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  • Author or Editor: Bernard B. Bible x
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Abstract

Five cultivars of tomato (Lycopersicon esculentum Mill.) grown in the season of 1973 and 3 cultivars of pepper (Capsicum annuum L.) grown in 1974 were classified into left-handed and right-handed plants respectively according to the clockwise and counterclockwise spiraling arrangement of their alternate leaves around and up the main stem. In 4 of 5 tomato and 2 of 3 pepper cultivars, total yield, in terms of both fruit weight and number of fruit was higher in right-handed than in left-handed plants. The results suggest that the regulation of foliar spirality can perhaps be used to advantage for increasing productivity of certain crop plants with alternate phyllotaxy.

Open Access

Silica sprays (Na2SiO3 or SiO2·nH2O) markedly reduced the incidence and severity of bract necrosis (BN) of Euphorbia pulcherrima Willd. cv. Supjibi Red compared to plants not sprayed with silica. BN has been associated with low Ca concentrations or high K: Ca ratios in tissues of bract margins. Silica had no effect on Ca or K concentrations in bract margin tissues, and BN was not associated with the macro- or micronutrient composition of bract margin tissues. Sixteen days after initial anthesis, nontreated and deionized-water-sprayed poinsettias developed a higher incidence of BN than did plants sprayed with Na2SiO3 or CaCl2. However, sprays of 3.56, 5.34, and 7.12 mm Na2SiO3 were as effective as 9.98 mm CaCl2 sprays in protecting against BN of `Supjibi Red' and `Angelika White' bracts for up to 30 days after initial anthesis. `Supjibi Red' developed a higher incidence of bract necrosis than did `Angelika White', but both cultivars showed a similar response to the treatments and similar symptoms of necrosis. In both cultivars, initial symptoms appeared as small necrotic lesions on bracts at the looped ends of lateral veins that displayed a closed-vein pattern after the plants reached initial anthesis.

Free access

Forty-two poinsettia cultivars were grown as a 15-cm single-plant pinched crop at 21/16.5°C (day/night) temperatures during Fall 1995 with standard commercial practices for irrigating, fertilizing, and pest control. On 7 Dec., 156 consumers rated the cultivars for their overall appeal. On 11 Dec., color coordinate (CIELAB) readings for bracts and leaves were taken with a Minolta 200b colorimeter. The colorimeter was set to illuminate C and has a 8-mm aperture. Bracts and leaves were placed on a white tile background for colorimetric readings. In 1996, a similar evaluation was conducted with 55 poinsettia cultivars. Using the L-value of leaves as a criterion, cultivars were separated into medium green-leafed and dark green-leafed groupings. For bracts among the red types, hue angle values were used to separate cultivars into cool red types (hue angle ≈20–22°) and warm red types (hue angle ≈24–25°). Based on the 1995 study, cultivars within the cool red bracts and dark green foliage group—those that were darker, duller red (lower L and chroma)—were less attractive (lower consumer ratings) than lighter, more-vivid red cultivars. For cultivars within the cool red bracts and medium green foliage group, consumers preferred the darker duller red cultivars. Perhaps dark foliage gives a more pleasing contrast with the more vivid cool reds than does the medium green foliage. In general, consumers rated red cultivars hire than non-red cultivars.

Free access

Poinsettia (Euphorbia pulcherrima Willd. ex. Klotzch) cultivars vary widely in susceptibility to bract necrosis, a disorder that has been associated with localized calcium deficiency. When `Supjibi Red' (SR) poinsettia shoots were grafted on `SR' stocks, a higher incidence of bract necrosis was observed (26.4% of bracts) 28 days after initial anthesis than on corresponding `SR' shoots grafted on `Annette Hegg Dark Red' (AH) stocks (13.8% of bracts). `AH' shoots developed few bract necrosis symptoms, regardless of rootstock. Calcium (Ca) concentrations were higher in whole bracts of `AH' than of `SR', but were unaffected by rootstock. In a second study, `SR' shoots were grafted on a double rootstock of one `AH' and one 'SR' to determine if removing either rootstock, at the start of flower initiation or at anthesis, affected bract necrosis. At 28 days after initial anthesis, `SR' scions on only `AH' roots from the beginning of flower initiation, or on `AH' roots from time of initial anthesis, had less bract necrosis (12.3% and 14.9%, respectively), than `SR' scions grafted on only `SR' roots from the onset of the study (24.2%). At harvest (36 days after anthesis), Ca concentrations in bract margin tissues were highest on `SR' shoots grafted to `SR' roots throughout the study [0.17% of dry mass (DM)], and lowest on shoots grafted to only `AH' from the time of flower initiation (0.15% of DM) or from time of initial anthesis (0.14% of DM). There was no significant correlation between Ca concentrations in bract margin tissue and bract necrosis. A single spray of benzyladenine to bracts, after bract necrosis symptoms first began to appear (at initial anthesis), totally arrested the further development of bract necrosis for up to 34 days. Similar treatment with daminozide increased the incidence of bract necrosis. This evidence suggests a new concept of bract necrosis etiology that includes a role for endogenous hormones. Chemical names used: N,N, dimethylaminosuccinamic acid (daminozide), N 6-benzylaminopurine (benzyladenine).

Free access

`Angelika White' poinsettias (Euphoria pulcherrima Willd.ex. Klotzch) were grown hydroponically with modified Hoagland's solution concentrations of 2 or 8 mS·cm-1. The 8-mS·cm–1 rate was imposed by proportionate increases in Ca(NO3)2, KNO3, and MgSO4. Water use, whole plant fresh mass, and pan evaporation were measured gravimetrically twice weekly over a 2-week period beginning 12 Oct. 1995. Poinsettia leaf water loss (g H2O/dm2 of estimated leaf area per day) was 0.30 and 0.22 times pan evaporation (g H2O/dm2 of pan area per day) for the plants in the 2 and 8 mS·cm–1 solutions, respectively (a 25% reduction in water loss for plants in the 8 mS·cm–1 solution), as compared to plants in the 2 mS·cm–1 solution. At initial anthesis, a reciprocal transfer of plants between the 2 and 8 mS·cm–1 solutions was used to investigate the time when plants were sensitive to high soluble salts for bract necrosis. Other plants were maintained throughout the experiment in the 2 and 8 mS·cm–1 solutions. On 15 Jan. 1996, plants were harvested and total lamina surface of leaves and bracts, number of necrotic bracts, and dry mass of leaves, bracts, stems, and roots were recorded. The results indicated that exposure to high soluble salts (8 mS·cm–1) prior to anthesis significantly increased the percent incidence of bract necrosis and decreased root growth. The smaller the root dry mass as a percent of total plant dry mass the greater the incidence of bract necrosis (Y = 0.0972X2 – 3.78X + 38.7, r 2 = 0.69).

Free access

The objective of this study was to determine the difference in color development between exposed and shaded fruit of `Loring' and `Raritan Rose' peach (Prunus persica L. Batsch). Chromaticity values (L* a* b*) were measured with a Minolta CR-200b colorimeter on 10 tagged fruit on each of 3 trees of each cultivar. Five fruit were fully exposed to sunlight and 5 were shaded. Measurements were made on each fruit from July 17, 1991 through harvest. Differences in the a*/b* ratio between shaded and exposed fruit were observed at the first sampling date and increased towards maturation; shaded fruit approached a*/b* values similar to exposed fruit at a significantly later time. Shading reduced relative fruit color development more in `Loring' than in `Raritan Rose'.

Free access

Differences in color development between exposed and shaded fruit during the growing season were determined for `Loring' and `Raritan Rose' peach (Prunus persica L. Batsch). The surface color of fruit exposed to sunlight in the upper canopy, and in the shade in the lower canopy, was measured with a tristimulus calorimeter, and L* a* b* values were recorded for each fruit from 17 July through harvest. Color changes (ΔE* ab) during maturation for both cultivars at either canopy position were characterized by large changes in hue (Δ H*ab) and lesser changes in lightness (Δ L*ab) and chroma (Δ C*ab). Upper canopy fruit of both cultivars were redder and darker than the lower canopy fruit initially and at harvest. Flesh firmness for `Loring' and `Raritan Rose' tended to correlate with color change from initial sampling to harvest.

Free access

Abstract

Little evidence is available concerning possible allelopathic effects of the thiocyanate ion (SCN-), a known toxin commonly found in plants of the Brassicaceae (crucifers). Seeds and seedlings of 39 species of crop plants were exposed to ionic thiocyanate (0.5 mM SCN- supplied as KSCN) to determine their relative sensitivity. Percent germination was unaffected by SCN- for all the species tested. Thiocyanate ion inhibited the total seedling (shoot and root) extension of 46% of the species tested, with 38% of the species showing inhibition of shoot and 49% showing inhibition of root extension. This demonstrates that SCN- has the capacity to harm a range of species. However, the toxicity was selective in that 44% of the test species were unaffected by exposure to SCN-. Wide differences in seed weight among species, in incubation time, and also systematics were major sources of variation for species sensitivity to SCN-.

Open Access

Poinsettias were grown in a closed hydroponic system with a modified Hoagland's solution concentration of either 1 or 3 mS·cm-1. Water use and whole plant fresh mass were measured gravimetrically at 2 to 3 day intervals over an eleven week period (initial break development through full bract development). At two week intervals, poinsettias were harvested and the fresh and dry mass of leaves, bracts stems, and roots were determined, and total laminar surface area was measured. Leaf temperature (LT), root-zone solution temperature (RZT), and at canopy level, air temperature (CAT), VPD, and photosynthetic photon flux (PPF) were monitored at 1 mm intervals and mean values recorded each 30 mm using a 21X micrologger (Campbell Scientific, Logan Utah). Water use (ml·dm-2·day-1) averaged 15% higher for poinsettias grown in the 1 mS·cm-1 solution than in the 3 mS·cm-1 nutrient solution. Simple linear regression of daily water use with PPF, or VPD, or CAT, while significant, accounted for less than half of the daily fluctuation in water use (r2; PPF= 0.47, VPD=0.21, CAT=0.30). However, multiple regression involving daily PPF, VPD, CAT, RZT and LT accounted for up to 82% of the variation in daily water use.

Free access