Leaf Yellowing in Easter Lilies: Causes and Solutions Progress Report –August 1995
Date 9/1/95
Title of Project Leaf Yellowing in Easter Lilies: Causes and Solutions
Institution where work is being conducted Clemson University and Purdue University
Amount of Endowment Grant $30,400
Covering Period 1/95 to 12/95
Anticipated Date of Completion/Final Report 12/95
Individual(s) Conducting Project:
(List Project Leader First)
Dr. William B. Miller - Title Associate Professor
Telephone Number 803-656-0898
Dr. P. Allen Hammer -Title Professor
Dr. Nihal Rajapakse - Title Research Associate
Mr. James Blake - Title Extension Associate
Leaf Yellowing in Easter Lilies: Causes and Solutions
William B. Miller, P. Allen Hammer, Nihal Rajapakse, James Blake
Clemson University and Purdue University
- A. Project Objectives:
- 1. Define and systematically study cultural practices that influence gradual (greenhouse) andcatastrophic (postharvest) leaf yellowing in Easter lily.
- 2. Evaluate potential remedial practices, including anti-senescence chemical treatments.
- 3. Develop cultural and/or other production guidelines, disseminated through trade literature andother sources, for the industry.
- B & C. Summary and Results of Work Completed to Date:
- During the past year we have conducted several new experiments as well as several follow-upexperiments on leaf yellowing disorders. Our earlier experiments indicated that leaf nitrogen and
carbohydrate levels are critical in regulating the leaf yellowing in Easter lilies. In 1995 spring, we
conducted two experiments to investigate the effects of nitrogen fertilization regimes on the growth
characteristics, leaf yellowing, and tissue nitrogen levels. In the first experiment, Easter lilies were
fertilized at each watering with 150, 300 or 450 ppm N (20-10-20 alternate with calcium nitrate plus
potassium nitrate) fertilizer solutions. Growth and timing characteristics (days to visible bud, days to
anthesis, number of leaves at anthesis, number of buds, and plant height) of lilies fed at different N
levels were not significantly different. Very little leaf yellowing was observed at the anthesis of all
plants. At the anthesis, plants were dissected to 3 sections (from top to bottom) and leaf chlorophyll
determinations were done. Leaf chlorophyll levels increased by about 10% from 150 ppm plants to
300 ppm plants in all the sections on the basis of fresh weight. From 300 ppm to 450 ppm, the
increase of chlorophyll level was not significant. Leaves, flower buds and stems were sampled and
freeze-dried for tissue nitrogen analysis.
- In the other experiment, effects of top dressing slow releasing N fertilizer on growth andtissue nitrogen was investigated. At 2 weeks after the emergence, in addition to the regular fertilizer
supplied at 200 ppm N with irrigation, plants were top-dressed with Nitroform (urea formaldehyde)
at the rate of half teaspoon or one teaspoon per plant. This top dressing was repeated one month
after the first application at the same rates in some plants. Growth and timing characteristics recorded
as in the above experiment were not affected significantly by the treatments. However, increased leaf
chlorophyll levels were observed with the top-dressing treatments. The increase was very clear in
upper leaves. Leaves, flower buds, and stems were sampled and freeze-dried for tissue nitrogen
analysis.
- An experiment was conducted to investigate the nitrogen and carbohydrate mobilization withinthe organs of Easter lilies during the entire growth period. Plants were sampled at weekly intervals
from the emergence to mature flower bud stage. Organs (bulb inner scales, bulb outer scales, leaves
at three sections from the top to bottom, stem, and flowers) were dissected and freeze-dried for
nitrogen and carbohydrate analysis. Nitrogen analysis showed that in the bulbs, tissue N
concentrations remained fairly constant during the growth in both inner and outer scales. However,
total nitrogen content of outer scales declined during the growth with the decrease of dry weight.
Inner scale N concentrations as well as contents did not fluctuate that much. Nitrogen content of other
organs (leaves, stems, and flowers) increased as the growth proceeded, and tissue N concentrations
fluctuated with no significant trend.
- Supplemental lighting during cold storage of mature plants has been shown to increase leafcarbohydrate levels in our earlier experiments. A follow-up experiment was conducted to check the
effects of supplemental lighting on tissue carbohydrate levels, and leaf yellowing. Mature Easter Lilies
were cold-stored (at 4′C) for 3 weeks in dark or under 50 umol*m-2*s-1 light provided by cool white
florescent lamps. Plants were sampled for leaf, stem and flower carbohydrate and nitrogen analysis
at weekly intervals. After 3 weeks of cold storage, plants were transferred to a postharvest room for
leaf yellowing observations. Cold-stored plants both under light and dark conditions showed severe
leaf yellowing symptoms. For example, about 40-50% of leaves turned yellow by 6 days at
postharvest room. Plants supplied with light, however, had about 10% lower leaf yellowing than
dark-stored plants. Flower longevity was slightly higher in light-supplied plants and bud abortion
was about 10% lower in light-supplied plants.
- Easter lilies grown under negative, zero or positive DIF in Purdue University were shipped toClemson in this season too. Then, plants were held in postharvest room for leaf yellowing
observations. Although the occurrence of leaf yellowing was higher in negative DIF grown plants
than positive DIF-grown plants, we haven’t seen remarkable difference as in our earlier experiments.
- D. Future Plans Covered by the Endowment Grant:
- We are continuing the nitrogen and carbohydrate analysis of tissue samples in above experiments. Atrade journal article on our earlier work was published in GrowerTalk. We are writing a scientific
journal article on these findings, and will be submitted to publication soon.
- E. Anticipated Beneflts for Floral Industry:
- While Easter lilies are among the most valuable crops on a square foot basis in U.S. floriculture, theysuffer from two potentially serious leaf-yellowing disorders: 1) a gradual yellowing of basal leaves
during forcing, and 2) “catastrophic yellowing” which mainly occurs during post-production shipping
and marketing. This disorder strikes quickly, causing a normal looking plant to turn almost entirely
yellow with a few days after cold storage. We are evaluating the cultural factors (growth regulators,
nutrition, fungicide application, high temperature forcing, shipping, and cold storage) which are
involved in these disorders. Our research is of great value to the industry for maintaining profitability
of the crop. If successful, it would allow confident handling and shipping of this crop and reduce
economic loss in the industry.
- Table 1. Growth and timing characteristics of Easter lilies fertilized at differentN concentrations Values are the means +/- SE of ten plants.
| Characteristic | Concentration of N in fertilizer solution | ||
| 150 ppm | 300 ppm | 450 ppm | |
| Days to visible bud | 69.6 ± 1.1 | 67.3 ± 0.6 | 68.3 ± 1.1 |
| Days to anthesis | 93.0 ± 0.4 | 92.9 ± 0.3 | 94.0 ± 1.0 |
| Number of leaves | 58.1 ± 1.4 | 57.1 ± 0.6 | 58.7 ± 1.0 |
| Number of yellow leaves | 4.4 ± 0.5 | 3.4 ± 0.4 | 1.6 ± 0.3 |
| Number of buds | 3.3 ± 0.4 | 3.4 ± 0.4 | 3.4 ± 0.3 |
| Stem length at anthesis (cm) | 35.4 ± 1.0 | 34.1 ± 1.1 | 35.1 ± 1.2 |
| Total height at anthesis (cm) | 46.8 ± 1.2 | 45.0 ± 1.2 | 45.6 ± 1.8 |
- Effects of slow-releasing-N application on growth and timing characteristics of Easter lily (1995 Spring)
| Characteristic | Control | Half tsp, once | Half tsp, twice | One tsp, once | One tsp, twice |
| Days to visible bud | 69.8 ± 0.8 | 69.7 ± 1.0 | 68.9 ± 0.8 | 68.2 ± 1.0 | 69.1 ± 1.0 |
| Days to anthesis | 93.3 ± 0.6 | 93.5 ± 0.6 | 93.6 ± 0.7 | 93.3 ± 0.7 | 94.2 ± 0.5 |
| Number of leaves | 54.1 ± 0.9 | 54.7 ± 0.9 | 55.3 ± 1.2 | 55.5 ± 0.9 | 55.3 ± 1.0 |
| Number of yellow leaves | 3.6 ± 0.6 | 2.0 ± 0.9 | 1.7 ± 0.4 | 2.9 ± 0.6 | 1.6 ± 0.4 |
| Number of buds | 3.0 ± 0.3 | 3.1 ± 0.2 | 3.1 ± 0.3 | 3.0 ± 0.3 | 3.1 ± 0.3 |
| Stem length at anthesis (cm) | 30.7 ± 0.9 | 31.5 ± 0.7 | 28.7 ± 0.5 | 30.7 ± 1.1 | 31.7 ± 1.4 |
| Total height at anthesis (cm) | 41.1 ± 1.3 | 41.4 ± 0.4 | 38.6 ± 0.7 | 41.1 ± 1.4 | 41.4 ± 1.2 |
