Nihal C. Rajapakse

End of day far-red light reverses height reduction of chrysanthemum induced by CuSO4 spectral filters

Abstract The response of cultivars ‘Bright Golden Anne’ (‘BGA’) and ‘Spears’ chrysanthemum plants to end of day-red (EOD-R) and end of day-far-red (EOD-FR) light was evaluated to determine the involvement of phytochrome in the regulation of plant morphology under CuSO4 filters. The CuSO4 spectral filters removed FR wavelengths and hence, increased the red:far-red (R:FR), blue:far-red (B:FR) and blue:red (B:R) ratios (R = 600–700 nm ; FR = 700–800 nm ; B = 400–500 nm) and ф of transmitted light compared with water (control) filter. Control plants were shaded with cheese cloth so as to attain the same photosynthetic photon flux (PPF) as in the CuSO4 chamber. Light transmitted through the CuSO4 filter significantly reduced height, internode length and stem dry weight of cvs. ‘BGA’ and ‘Spears’ chrysanthemum plants. However, the degree of response varied with the cultivar. Exposure to EOD-FR reversed the reduction of plant height, internode length and the stem dry weight caused by the light transmitted through CuSO4 filters to a level comparable with plants that received no EOD treatment under control. Exposure to EOD-R light reduced the height and stem dry weight of ‘BGA’ plants grown under the control filter, but had no effect under the CuSO4 filter. Exposure to EOD-FR did not significantly alter height and stem dry weight under control filters. In ‘Spears’ plants, EOD-R caused stem dry weight reduction under control filters, but did not reduce stem or internode elongation. The results suggest that phytochrome may be involved in controlling plant response under CuSO4 filters. However, there is evidence to indicate that an additional mechanism may be acting on stem/internode elongation.

Influence of spectral filters on growth and postharvest quality of potted miniature roses

Abstract The role of light quality on growth and postharvest characteristics of potted miniature roses (Rosa × hybrida cultiver ‘Meijikatar’) was evaluated using 6% CuSO4 and water (control) as spectral filters. The CuSO4 spectral filters reduced R and FR wavelengths and increased the R:FR, B:FR and B:R ratios (R = 600–700 nm; FR = 700–800 nm; B = 400–500 nm) and o of transmitted light compared with control filter. Light transmitted through the CuSO4 filter significantly reduced plant height and internode length and increased the number of lateral shoots compared with control plants. However, the degree of response varied with growing season. CuSO4 filters slightly accelerated flowering in early spring-grown plants but slightly delayed flowering in late spring and summer. Total number of flowers was not affected by spectral filter but plants grown under control filter had larger flowers than those grown under the CuSO4 filter. Light transmitted through CuSO4 filter reduced leaf sucrose and starch concentration by 40% and 65%, respectively. Leaf glucose and fructose concentrations were not affected by light quality. Postharvest quality of plants grown under CuSO4 and control filters was reduced and leaf yellowing increased as the shipping temperature increased. Light quality in the growing environment did not significantly reduce the overall appearance of plants shipped at 4°C or 15°C. However, plants grown under CuSO4 filter had slightly higher percentage of yellow leaves than the corresponding control plants after shipping at any temperature. Alteration of light quality in the greenhouse can be used to control height of rose plants but extended shipping at high temperatures could result in leaf yellowing possibly because of reduced carbohydrate status.

Sucrose Concentration in Liquid Media Affects Soluble Carbohydrates, Biomass and Storage Quality of Micropropagated Hosta

The effects of sucrose concentration (1, 3, 5, or 7% w/v) in liquid media, in the presence and absence of benzylaminopurine (BAP), on internal carbohydrate status and growth of Hosta tokudama Tratt. ‘Newberry Gold’ during the multiplication phase (stage II) was investigated. Cultures from all treatment combinations were transferred to media containing 3% (w/v) sucrose during the rooting phase (stage III). At the end of the stage III, these micropropagules were subjected to 5 weeks of storage at 10 °C under low light (photosynthetic photon flux of 5 µmol m−2s−1). Endogenous concentrations of soluble sugars (glucose, fructose, and sucrose) in the plantlets increased linearly as the media sucrose concentration increased from 1% to 7% during stage II. Root and shoot biomass increased with increasing media sucrose concentration. BAP increased the biomass and multiplication rate but did not affect internal concentration of soluble sugars. While in storage, endogenous sugar levels and plantlet dry weight remained unchanged for all treatments. Following storage, plants originally cultured in 5% and 7% media sucrose had higher dry weight and less leaf chlorosis than those cultured in 1% and 3% media. Differences in endogenous soluble sugar levels at the end of stage III rooting, and after storage were related to the sucrose concentration of the initial stage II multiplication medium. Increased media sucrose levels during the multiplication cycle has a positive, long-term effect on plant morphology and quality.

Vacuum infiltration with calcium chloride influences oxygen distribution in apple fruit flesh

Abstract Oxygen distribution within flesh tissues of ‘Coxs Orange Pippin’ and ‘Braeburn’ apples was determined following vacuum infiltration with solution. Vacuum infiltration with 0.2 M calcium chloride (CaCl 2 ) solution and, to a lesser extent, with water increased estimates of skin resistance to O 2 diffusion and resulted in reduced O 2 levels in tissues beneath the skin and in the central core cavity. Gradients in O 2 concentration across skin and flesh tissues were increased by vacuum infiltration but the proportional increase in O 2 gradient across the flesh tissues was higher than the gradient across the skin. These effects were due to decreased O 2 diffusivity in flesh tissues and increased skin resistance to gas diffusion. Vacuum infiltration effects on O 2 concentration gradients declined with time. Development of controlled or modified atmosphere (CA/MA) storage techniques for vacuum infiltrated fruit should take account of the altered O 2 distribution characteristics within flesh tissues to avoid detrimental effects on internal quality.

Influence of CuSO4 spectral filters, daminozide, and exogenous gibberellic acid on growth ofDendranthema Xgrandiflorum (Ramat.) Kitamura ‘bright golden anne’

The response of chrysanthemum plants to gibberellic acid (GA3) and daminozide, grown under 6% CuSO4 and water (control) spectral filters, was evaluated to determine the involvement of gibberellins in regulation of plant height under CuSO4 filters. The CuSO4 filter increased the red (R)/farred (FR), and blue (B)/R ratio (R=600–700 nm; FR =700–800 nm; B=400–500 nm) of transmitted light. PPF under 6% CuSO4 filter was reduced by about 34% compared to PPF under water filter which averaged about 750 μM·m−2·s−1. Control plants were shaded with Saran Wrap to ensure equal PPF as in the CuSO4 chamber. GA3 application increased plant height under both the control and CuSO4 filter, but the height increase under the CuSO4 filter was about 20% greater than that under the control filter. Daminozide treatment reduced plant height under the control and CuSO4 filter, but the height reduction in control plants was slightly greater than under the CuSO4 filter. The height reduction caused by daminozide was prevented by GA3 application in plants grown under the control or CuSO4 filter. The results suggest that GA3 may be partially involved in height reduction under CuSO4 filters.

Post-production stability of parthenolide in feverfew (Tanacetum parthenium)

ABSTRACT The influence of pH, temperature and light on parthenolide (PRT) content of feverfew was investigated. Feverfew powder and PRT standards mixed in citrate buffers at selected pH (2.4-7.2) were stored for four months. PRT declined in all treatments with greatest loss in solutions with pH below 5, and highest stability in solutions with pH 7.2. PRT in dry samples declined 30 percent after 320 days of storage. Degradation of PRT in feverfew solutions exposed to 40, 60, and 80°C for 24 h increased with increasing temperature. Dry samples exposed to various temperatures revealed stability of PRT at temperatures up to 130°C for short time periods.

Sucrose in storage media and cultivar affects post-storage regrowth of in vitro Hosta propagules

The goal of this research was to investigate if culturing in high sucrose (5%) liquid media during multiplication phase (stage II) would enhance endogenous sugar levels and dry matter sufficiently to allow storage of in vitro plants in sugar free media without adversely affecting post-storage recovery. Hosta tokudama ‘Newberry Gold (NBG)’ and Hosta ‘Striptease’ were cultured in Murashige and Skoog (MS) media containing 5% sucrose during stage II and transferred to rooting phase (stage III) in MS medium without (0%) sucrose or with 3% sucrose for 4 weeks. At the end of stage III, cultures were stored, with the remaining media, at 10 °C with 5 μmol m−2 s−1 photosynthetic photon flux (PPF) from cool white fluorescent lamps for 7 or 14 weeks with or without a 2-week dark period prior to removal from storage. In both cultivars, stage III plants cultured in 3% sucrose media had higher soluble sugar levels and greater shoot and root biomass than those cultured in 0% sucrose media. Shoot and root soluble sugars decreased during storage. Shoot growth ceased during storage in both media. Root dry matter continued to increase in plants stored in 3% sucrose media but did not change in 0% sucrose media. Plants cultured in 3% sucrose media had less leaf chlorosis and less mortality after 7 or 14 weeks of low temperature storage than the plantlets from sugar free media. Extending the storage period from 7 to 14 weeks or introduction of 2-week dark period at the end of storage did not affect leaf chlorosis or plant mortality during acclimatization. Post-storage growth varied with the cultivar. Benefit of having sucrose in storage media was to develop a strong root system that aided the acclimatization and post-storage growth following 7 or 14 week storage. Sucrose ‘loading’ by culturing plants in liquid media containing 5% sucrose did not allow storage in sugar free media without adversely affecting post-storage growth in both cultivars.

Carbohydrate status and postharvest leaf chlorosis of miniature roses as influenced by carbon dioxide enrichment

Abstract The effect of CO2 enrichment on carbohydrate status and postharvest leaf chlorosis of potted ‘Meijikatar’ miniature roses was investigated. Plants were grown in 350, 700 or 1050 μl l−1 CO2 until they reached flower bud coloration and placed into dark storage at 4°C or 16°C for 5 days to simulate shipping before placing in an interior environment with a photon flux of 30 μmol m−2 s−1 from cool white fluorescent light source for postharvest evaluation. Stomatal resistance was increased (∼25%) and aperture was decreased (∼36%) by 700 or 1050 compared to 350 μ1 1−1 CO2. The higher CO2 levels slightly (10%) increased leaf sucrose concentration, had no effect on stem sucrose concentration, and had little effect on whole plant reducing sugars. Leaf and stem starch concentration increased over three-fold as CO2 increased from 350 to 700 μ1 1−1. Regardless of storage temperature, carbon dioxide enrichment did not affect the overall visual quality or percentage leaf chlorosis after 5 days in the interior environment. Regardless of CO2 level, plants stored at 16°C showed three-fold increase in leaf chlorosis compared to plants stored at 4°C. Although CO2 enrichment increased the carbohydrate pools of the plants, our results do not support the hypothesis that increased carbohydrate supply plays a role in reduction of postharvest leaf chlorosis of potted miniature roses.

Height Control of Vegetable Seedlings by Greenhouse Light Manipulation

ABSTRACT The response of bell pepper and watermelon transplants to rigid photoselective plastic panels with four concentrations of a far red (FR) light absorbing dye was tested to develop greenhouse light manipulation as a non-chemical alternative for height control. Far red light interception increased, and transmission of photosynthetic photon flux (PPF) decreased as dye concentration increased. Light transmitted through photoselective panels reduced height of bell pepper and watermelon seedlings by ≈ 30%. The shoot dry weight of plants was also reduced with increasing dye concentration. Rigid panels with a higher dye concentration were slightly more effective in reducing plant height but the reduction in PPF with increasing dye concentration can adversely affect plant growth and development. Based on initial results, photoselective, polyethylene films were produced with a dye concentration that resulted in 75% light transmission (phytochrome photoequilibrium of 0.80) for further testing. The response of cucumber, tomato, and bell pepper seedlings was evaluated under photoselective films with two different types of dyes that reduced light transmission by 75%. Cucumber seedlings were more responsive to filtered light than tomato or pepper seedlings. Developmental rate, measured as the rate of node production, was not affected. Photoselective films reduced total shoot dry matter of cucumber and bell pepper. Smaller plants as opposed to a reduction in dry matter production primarily caused the shoot dry weight reduction under the photoselective filters. Significant reduction in stem elongation can be achieved by exclusion of FR light at the end of the day by covering west and south facing walls of the chambers or by exposing plants to photoselective films at the end of the day. However, continuous exposure of the plants to the photoselective films was most effective in reducing stem elongation.

Use of Low Temperature to Improve Storage of in vitro Broccoli Seedlings Under Various Light Qualities

ABSTRACT Broccoli (Brassica oleracea L. Botrytis Group ‘Green Duke’) seeds were germinated in vitro photoautotrophically (without sugar in medium) or photomixotrophically (with sugar in medium) for 3 weeks at 23 ° C and 150 μmol · m−2 · s−1 photosynthetic photon flux (PPF). Vessels were then stored at 1 ± 0.35°C under 1.6 ± 0.20,4.1 ± 0.35, or 8.6 ± 0.50 μmol · m−2 · s−1 constant PPF each of white (400–800 nm), red (600–700 nm), or blue (400–500 nm) light. Concentrations of CO2 inside the vessels were monitored until equilibrium was reached. Light compensation point was reached at