Marigold Seedlings Research Articles

Use of Digital Analysis of Radicle Extension of Marigold Seedlings as an Early Indicator of Seed Vigor

Several seed vigor tests were conducted on Marigold `Little Devil Flame' and correlated with digital analysis of radicle extension. Seed from a single lot was deteriorated by the accelerated aging (AA) method at 41 °C for 24 and 72 h. Seed moisture content of unaged seed was 15.23%, mildly aged seed (24-h AA) was 40.77%, and moderately aged seed (72-h AA) was 52.85%. After AA treatment, all seeds were dried to near 15% moisture. Vigor level was assessed 7 days after AA treatment by standard germination and soilless-mix plug emergence tests according to the Association of Official Seed Analysts Rules for Testing Seed. The standard germination test revealed an 84.5% germination for unaged seed, 49.5% germination for mildly aged seed, and 28.5% germination for moderately aged seed. The plug emergence test showed an 88.9% normal emergence for unaged seed, 65.28% germination for mildly aged seed, and 9.72% germination for moderately aged seed. Additionally, the radicle of seedlings established under standard germination conditions was digitally analyzed after 4 days. According to digital analysis, average radicle length for unaged seed was 2.10 cm, 1.91 cm, for mildly aged seed, and 1.27 cm for moderately aged seed. Radicle length after 4 days showed an R2 of 0.81 when regressed against standard germination and an R2 of 0.99 with seedling emergence tests. These results suggest that digital analysis of radicle extension could provide a sensitive, reproducible test for seed vigor.

Regulation of Greenhouse Night Temperature Based on Total Carbohydrate Concentration and Night Length

The relationship between initial total non-structural carbohydrate concentration (TNCi) in marigold seedlings, night temperature, and night length were evaluated. Seedlings containing an average of 7.2, 18.1, and 23.5 mg/100 mg dwt of nonstructural carbohydrate (TNC) at sunset were treated with night temperatures of low (10°C), medium (17°C), and high (24°C). Starch and soluble sugars were determined at intervals during the night. TNC concentration at the end of the night is a function of the night temperature, TNCi concentration at sunset, and the night length. A model describing the relationship of these variables and their interactions was derived to estimate TNC concentration at any time during the night. This model when solved for temperature (t) establishes a temperature that will regulate the metabolic rate so the TNC concentration is metabolized efficiently to some minimum concentration by the end of the dark period. t = (–2.93 + 1.14 TNCi + 0.74 T – TNC – 0.48 TNCi * T)/(–0.18 + 0.011 TNCi + 0.04*T), R2 = 0.88**). Thus, by knowing TNCi (possibly by near-infrared spectroscopy), the length of the night, and, assuming some minimum concentration for TNC by the end of the dark period, the night temperature is established.

Marigold Root Growth in 12-cm Containers Modified with Two or Four Copper-treated Inserts

This study evaluated the effect of container shape and copper hydroxide on root and shoot development of marigold (Tagetes patula `Little Devil Flame') seedlings. Containers were modified in shape and volume by gluing triangular polycarbonate inserts vertically onto sides of the container. The inserts were either painted with copper or not painted. Inserts decreased container volumes (no insert = 480 cm3, two inserts = 340 cm3, and four inserts = 200 cm3). After 38 days the seedling roots were scanned for computer analysis, and leaf area and dry weights were determined. Copper effectively prevented roots from growing in contact with copper treated surfaces. Shoot dry weight and leaf area were greater with no inserts, but if inserts were treated with copper the shoot dry weight and leaf area were greater. Root dry weight was reduced 7%–10 % with two inserts and 20% with four inserts compared to no inserts. Copper treated inserts reduced the dry weight further. However, at the insert interface, root length was increased between 15%–20% by all copper treatments, with the greatest increase in the four-insert treatment.

Container Volume and Height Affect Shoot and Root Development in Marigold Seedlings

Marigold seedlings were grown in four containers that differed in both volume and shape. Seedlings grown in 1.5-gal containers showed the greatest potential for shoot and root development 20 days after sowing. These seedlings had greater leaf area, shoot and root dry weight, and total root number and length compared to seedlings grown in 406 plug trays, 72-cell packs, or 6-inch containers. There was a positive correlation (r2 = 0.81) between cell volume and seedling growth as well as a positive correlation (r2 = 0.89) between container height with seedling growth. An attempt was made to separate the impact of container volume vs. container height on seedling growth. Containers were designed using acrylics to vary the container height while keeping the volume constant at 1500 cm3. There was a positive correlation (r2 = 0.87) between shoot and root dry weight with container height. The data suggest that both container volume and height contribute to overall seedling growth in marigold, but when container volume is not limiting, container height has a large impact on seedling development.

Copper Hydroxide is an Effective Control of Root Outgrowth in Plug-grown Seedlings Subirrigated by Capillary Mats

Capillary mat subirrigation provides uniform water in the growing medium to optimize seedling growth in plugs. It also offers a closed system that allows the grower to regulate the amount of water available to seedlings and to reduce water runoff. However, root outgrowth into the capillary mat can be a significant problem. Copper hydroxide (Spin Out) was painted on the bottom, outside surface of the plug container to control root outgrowth into the capillary mat. Three square and two octagonal plug sizes were treated with copper. Regardless of the plug size or shape, copper treatment was an effective treatment to control root outgrowth in marigold seedlings. Copper treatment reduced overall root outgrowth by 80% to 92%. Marigold and geranium seedlings in copper-treated square plug containers showed some reduced shoot and root development during plug production, but there were no differences in copper-treated plants compared to nontreated plants following transplanting to cell packs.

Leaching Characteristics of P From Four Fertilizer Sources in a Container Nursery Growing Medium

A 3 pine bark: 1 peatmoss: 1 sand (by volume) medium was amended with 7.7 g P as superphosphate, triple superphosphate, ammonium phosphate, or controlled-release ammonium phosphate per 1000 g medium (3.8 liters). The medium was then leached with 250, 350, or 450 ml distilled, deionized water daily for 25 days. Phosphorus leaching curves were then generated for each fertilizer. A subsequent study determined the effect of these four P fertilizers on growth of marigold seedlings in the greenhouse. Superphosphate, triple superphosphate, and ammonium phosphate rapidly leached from the medium, while the controlled-release ammonium phosphate was retained for a longer time. Marigold growth was not affected by fertilizer type; however, marigolds grown in P-amended media were larger than those grown without P. These studies indicate that amending container growing medium with superphosphate or triple superphosphate prior to planting may not be cost-effective.

The effects of addition of Trichoderma inocula on flowering and shoot growth of bedding plants

Trichoderma isolates were added to a range of peat-based growing media as a dried fermenter biomass to study the prospects of general use in promoting bedding plant growth. The responses of marigold plants in peat/grit compost, petunia plants in peat/sand compost and verbena plants in Fisons M2 compost to inoculation with a range of Trichoderma strains applied as dry fermenter biomass were studied. In tests with marigold seedlings, T. harzianum strains WT, T35 and 20 and T. viride strain 47 applied at a rate of 1% w/v showed increases in shoot fresh and dry weights of up to 40% and 52%, respectively, and T. harzianum strains T35 and 20 increased the number of flowers by up to 40%. In tests with petunia plants, T. harzianum strain TH1 applied at a rate of 0.1% w/v increased the shoot fresh weight by 82% and dry weight by 87%. The number of flowers and buds were increased with strain TH1 at application rates of 0.1% and 0.01% w/v and with T. harzianum strain T12B applied at a rate of 0.1% w/v by up to 227%. In tests with verbena seedlings, T. harzianum strains WT and 20 and T. viride strains 75, 92 and T8 were applied at 0.3, 0.7 and 1.0% w/v. Depending on concentration, each strain was able to increase either number of flowers, weight of flowers, shoot fresh weight or shoot dry weight, but only WT applied at 1% w/v increased all these parameters. Thus Trichoderma biomass can increase flowering and shoot growth of petunia, marigold and verbena under a range of cultural conditions.

781 PB 421 RAPID ANALYSIS OF CARBOHYDRATE CONCENTRATIONS IN MARIGOLD LEAF TISSUE USING NEAR INFRARED REFLECTANCE SPECTROPHOTOMETRY

Studies were conducted to determine if near infrared reflectance spectrophotometry (NIR) could be used to rapidly determine nonstructural carbohydrate (TNC) concentrations in marigold tissue. Marigold seedlings were grown in natural light growth chambers. Light intensity and CO2 concentration were adjusted to establish leaf samples with a wide range of the carbohydrate concentration. NIR spectra were collected on dry, ground samples using a reflectance scanning monochromator. Conventional laboratory analysis values for the same samples were correlated with spectral data. Calibration statistics were as follows: TNC; standard error of calibration (SEC)= 1.73, R2= 0.95, standard error of prediction or perfomance (SEP) = 1.64, R2= 0.95; Starch, SEC = 1.35, R2= 0.96, SEP = 1.37, R2= 0.94; Soluble Sugars, SEC = 0.26, R2= 0.91, SEP = 0.29, R2= 0.84. These results show that the NIR method can be used to rapidly determine concentrations of nonstructural carbohydrates in marigold leaf tissue and suggest the possibility for routine assessment of carbohydrate status for optimum management of environmental factors.

507 PB 251 DETERMINATION OF OPTIMUM GREENHOUSE NIGHT TEMPERATURE FOR MARIGOLD SEEDLINGS BASED ON STARCH CONCENTRATION AND SEEDLING GROWTH

Through control of light intensity and CO, concentrations, three levels of starch (low, medium and high) in marigold seedlings existed at sunset. The range in starch concentration represented that encountered under average greenhouse conditions. For each starting starch concentration, an optimum temperature was initially determined based on first and second order reactions on the corresponding starch decline curve. Every day, during seedling growth in the greenhouse, the starch concentration at sunset was predicted based on primarily the quantity of light received throughout the day; the night temperature was adjusted to the predicted optimum night temperature setting. Based on these studies a significant improvement in seedling growth can be achieved with significantly less heating cost.

SEQUENTIAL EFFECTS OF CARBOHYDRATE ACCUMULATION AND CONSUMPTION IN MARIGOLD SEEDLINGS

Supplemental CO2 of 1500 μl/l with radiation of 35 mols/day/m2 resulted in a daily net accumulation of 60% increase in starch and 100% increase in soluble sugars at the end of the light period compared to seedlings grown at ambient CO2. During low solar radiation periods the net daily accumulation of starch and soluble sugars was very little in seedlings grown with or without supplemental CO2. At night, the concentration of starch decreased linearly with time, whereas soluble sugars decreased only slightly. The greater the concentration of carbohydrates at sunset the greater the metabolism of carbohydrates at night. When solar radiation was between 30-60 mols/day/m2, the greater the concentration of starch in seedlings at the end of the dark period the lower the net daily accumulated starch at the end of the next day. Also higher night temperatures (23° vs. 8°), which maintained high metabolism of starch at night and thus a lower starch concentration at sunrise the next day, was correlated with greater net accumulated starch at the end of the next day. These results indicate that starch may inhibit photosynthesis in marigold seedlings; thus cultural practices that maintain low starch accumulation or high metabolism may enhance photosynthesis.

MODIFIED ATMOSPHERE PACKAGING OF BEDDING PLANTS AND PLUG SEEDLINGS

Poor post-production handling of bedding and seedling plants by mass-market outlets causes substantial quality reductions and product losses. Modified atmosphere packaging (MAP) may be a means to extend postharvest longevity and ease bedding plant handling. MAP, using heat sealed polyethylene bags, was tested with pansy, marigold, geranium, impatiens, California poppy, gazania, tomato, and pepper seedlings. Equilibrium O2 levels of 5-15% were generally reached within one to two weeks, while CO2 increased to 5% or more of the package atmosphere at equilibrium. Ethylene accumulated to more than .5ppm within 24 hours in some packages. Marigold seedlings had obvious leaf and stem distortion after 2-3 days. Maximum useful storage time varied from 2 weeks for tomato to greater than 8 weeks for pansy at 10C. Tomato and pepper seedlings were test marketed at a local supermarket.

EVALUATION OF METHODS TO PREVENT ROOT GROWTH INTO CAPILLARY MATS

To prevent rooting into an irrigation mat, five water porous materials, perforated black plastic, perforated ground cover, polyester, woven polypropylene and porous plastic, were evaluated as mat covers. Only polyester, woven polypropylene and porous plastic prevented penetration of roots of marigold seedlings into the mat. Under high moisture stress, root tips were killed at the cell drainage hole; however, under low moisture stress the roots formed a mat on top of these mat covers. To prevent root penetration out the drainage hole, polyester and porous plastic were glued over the hole. No difference in shoot growth was observed between the control (only polyester mat cover) and seedlings produced in drainage hole covered cells. Total root growth of plug seedlings with drainage hole covered were greater than the control. Ten days after transplanting, seedlings that had been produced in plugs, with covered drainage holes, were larger.

ACCUMULATION AND METABOLISM OF CARBOHYDRATES IN MARIGOLD SEEDLINGS

Marigold seedlings, 3 weeks old, were grown in natural light growth chambers at 3 day/night temperature regimes, 8°N/16°D, 13°N/20°D and 18°N/24°D, in a factorial combination with ambient and 1000-1500 ppm CO2. Seedlings were harvested at regular intervals during a 24 hr period and were analyzed for soluble sugars (reducing sugars and sucrose) and starch. Neither temperature nor CO2 concentration affected the accumulation of soluble sugars or starch during the day or night. The soluble sugar concentration ranged from 3% of dry weight at sunrise to 6% at mid-day; the concentration changed little during the night. Light intensity was different during replications of the experiment. Increased light intensity appeared to cause a slight increase in the soluble sugars maintained by the seedling during the day. Accumulated starch increased 6% to 8% from sunrise to late afternoon. Preliminary results indicate that light intensity greatly affected the concentration of starch. On the higher light intensity day, starch accumulated to a maximum of 18% of dry weight; whereas on the lower light intensity day the maximum concentration was 10%. During the night following the lower light intensity day, the starch concentration decreased to approximately 3% by the end of the night; following a brighter day the starch content was 13% at the end of the night.

Growth Retardants Affect Landscape Performance of Zinnia, Impatiens, and Marigold

Various spray rates of paclobutrazol, 5000 ppm daminozide, 200 ppm ancymidol, or drought imposition (visible wilt symptoms for up to 2 hours daily) were applied to three bedding plant species to determine effects on growth in the greenhouse and the subsequent growth and performance of treated plants in the landscape. Seedlings of Zinnia efegans Jacq. `Peter Pan Scarlet' responded to all growth retardants (paclobutrazol at 40 and 90 ppm) and the drought treatment in the greenhouse. However, zinnias treated with paclobutrazol or ancymidol still exhibited reductions in plant height 5 and 7 weeks after transplanting to the landscape, and in plant quality (subjective rating of plant appearance with emphasis on flower cover) at 5 weeks after transplanting. Daminozide or drought controlled zinnia growth in the greenhouse but had no carry-over effect in the landscape. Stem elongation of Impatiens wallerana Hook `Accent Red' seedlings was moderately controlled by 20 ppm paclobutrazol in the greenhouse. There were no other treatment effects in the greenhouse. Paclobutrazol (20 ppm) reduced final plant height and quality (7 weeks postplanting). Treatment with daminozide or drought reduced plant width and quality after 5 and 7 weeks in the landscape. Ancymidol had no effect on landscape performance of impatiens. Shoot dry weight gain and stem elongation of Tagetes erects L. `Papaya Crush' seedlings were reduced by ancymidol or 40 ppm paclobutrazol in the greenhouse. Shoot dry weight gain of marigold seedlings was inhibited during the first week of landscape establishment by prior treatment with daminozide, ancymidol, or drought. Final plant height and width in the landscape were not affected by any treatment; however, 40 ppm paclobutrazol, daminozide, or ancymidol decreased final plant quality. Chemical names used: α -cyclopropylα -(4-methoxyphenyl) -5-pyrimidinemethanol (ancymidol); butanedioic acid mono(2,2-dimethylhydrazide) (daminozide); β -[(4-chlorophenyl) methyl] - β - (1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol).

Container Size and Shape Influence Growth and Landscape Performance of Marigold Seedlings

Seeds of marigold (Tagetes erects L. `Janie') were sown in flats of three cell sizes (inverted pyramids, Todd 080A, 100A, or 175; volume 7, 24, or 44 cm3, respectively) or in flats of different root cell configurations [Todd 100A, Grow-Tech (GT) 200, or Growing Systems (GS) 135; shaped as inverted pyramid, cylinder, or cylinder with a bottom lip, respectively]. During 2 consecutive years, plants grown in Todd 080A trays had 60% less leaf area and shoot and root dry weights than plants grown in Todd 175 trays. Plants grown in Todd 100A trays had 30% less leaf area and shoot and root dry weights than plants grown in the larger volume tray. Stem length was less affected by container size. The rate of shoot dry weight gain during the 3 weeks after transplanting in the field was greater in plants from the smaller containers (Todd 080A and Todd 100A) in 1987. Final height (7 weeks after planting) of plants from Todd 080A or Todd 100A flats was 12% and 7% less, respectively, than those of plants grown in Todd 175 flats, while final plant quality was reduced 34% and 21%, respectively, in plants from these flats in 1987. Similar, but smaller, effects were recorded in 1988. Container type had little effect on plant growth in the greenhouse and no effect on growth in the landscape. The maximum quality rating in the landscape, awarded to plants from Todd 100A flats, was 12% greater than that of plants from GT 200 flats in 1987 and 5% and 9% greater than plants from GT 200 and GS 135 flats, respectively, in 1988. Final plant performance of marigold seedlings was reduced more by root restriction or transplant size than previously reported with vegetable species.

Effects of Relative Humidity and Type of Container on the Growth of F 1 Hybrid Annuals in Controlled Environments

The effects of three levels of relative humidity (40%, 65%, and 90%) and two types of containers (clay and plastic) on the seedling growth of three F1 hybrid annuals were determined after 14 days of controlled-environment treatment. Forty percent relative humidity was severely limiting to the seedling growth of ‘Blue Blazer’ ageratum (Ageratum houstonianum Mill.), ‘Pink Cascade’ petunia (Petunia hybrida Vilm.), and ‘Double Eagle’ marigold (Tagetes erecta L.). Raising the relative humidity to 65% resulted in striking increases in fresh weight, dry weight, and leaf area, especially when clay containers were used. Height of the main shoot was increased significantly at 65% relative humidity but node number was influenced only slightly. Increasing the relative humidity further to 90% had no significant effect on fresh weight, dry weight, or percent dry weight for any of the three species, in either container. Leaf area was increased significantly at 90% only in ageratum seedlings grown in clay pots. Each species responded differently to the type of container used. The fresh weight and dry weight of petunia seedlings were significantly greater in plastic pots at every level of humidity while those of marigold seedlings were unaffected by the type of container used. Ageratum seedlings, on the other hand, had significantly greater fresh weights and dry weights in clay pots only at 90% relative humidity.

EFFECTS OF RELATIVE HUMIDITY AND TYPE OF CONTAINER ON THE GROWTH OF F1 HYBRID ANNUALS IN CONTROLLED ENVIRONMENTS

The effects of three levels of relative humidity (40%, 65%, and 90%) and two types of containers (clay and plastic) on the seedling growth of three F1 hybrid annuals were determined after 14 days of controlled‐environment treatment. Forty percent relative humidity was severely limiting to the seedling growth of ‘Blue Blazer’ ageratum (Ageratum houstonianum Mill.), ‘Pink Cascade’ petunia (Petunia hybrida Vilm.), and ‘Double Eagle’ marigold (Tagetes erecta L.). Raising the relative humidity to 65% resulted in striking increases in fresh weight, dry weight, and leaf area, especially when clay containers were used. Height of the main shoot was increased significantly at 65% relative humidity but node number was influenced only slightly. Increasing the relative humidity further to 90% had no significant effect on fresh weight, dry weight, or percent dry weight for any of the three species, in either container. Leaf area was increased significantly at 90% only in ageratum seedlings grown in clay pots. Each species responded differently to the type of container used. The fresh weight and dry weight of petunia seedlings were significantly greater in plastic pots at every level of humidity while those of marigold seedlings were unaffected by the type of container used. Ageratum seedlings, on the other hand, had significantly greater fresh weights and dry weights in clay pots only at 90% relative humidity.