Hans Ragnar Gislerød

Combined influence of light and temperature on growth rates of Nannochloropsis oceanica: linking cellular responses to large-scale biomass production

The interaction effects between irradiance and temperature on growth rates ofNannochloropsis oceanicawere determined in both laboratory cultures and large-scale tubular photobioreactors. Growth responses were investigated in 48 batch cultures subjected to crossing light/temperature gradients ranging from 34–80μmol photons m−2s−1and 14.5–35.7∘C respectively. Comparisons were made to growth responses observed in production systems (200L biofences) operated in climate-regulated greenhouses with controlled temperature and artificial light gradients. Cellular responses showed increasing specific growth rates as a function of temperature, with a peak at 25–29∘C, after which the growth became increasingly unstable. The optimum temperature for growth increased with higher light intensities up to approximately 28∘C at 80μmol photons m−2s−1. At low light intensities the specific growth rate was less affected by temperature. The maximum daily production measured in the biofence systems increased proportionally with irradiation and reached approximately 0.7gL−1d−1at 1030μmol photons m−2s−1average daily radiation for a culture temperature of 24∘C. This corresponds to a daily yield of 140g per day in a 200L biofence system. When specific growth rates for the biofence cultures were measured at different densities and plotted against temperature, results showed a peak with the 24∘C temperature treatment. This peak became less pronounced as the density increased in the cultures. This is consistent with the laboratory results; increasing cell density in the biofence cultures resulted in less average light cell−1, which produced the same temperature dependent response as seen by reducing the external irradiance exposure for the dilute laboratory cultures.

High relative air humidity and continuous light reduce stomata functionality by affecting the ABA regulation in rose leaves

Plants developed under high (90%) relative air humidity (RH) have previously been shown to have large, malfunctioning stomata, which results in high water loss during desiccation and reduced dark induced closure. Stomatal movement is to a large extent regulated by abscisic acid (ABA). It has therefore been proposed that low ABA levels contribute to the development of malfunctioning stomata. In this study, we investigated the regulation of ABA content in rose leaves, through hormone analysis and β-glucosidase quantification. Compared with high RH, rose plants developed in moderate RH (60%) and 20 h photoperiod contained higher levels of ABA and β-glucosidase activity. Also, the amount of ABA increased during darkness simultaneously as the ABA-glucose ester (GE) levels decreased. In contrast, plants developed under high RH with 20 h photoperiod showed no increase in ABA levels during darkness, and had low β-glucosidase activity converting ABA-GE to ABA. Continuous lighting (24 h) resulted in low levels of β-glucosidase activity irrespective of RH, indicating that a dark period is essential to activate β-glucosidase. Our results provide new insight into the regulation of ABA under different humidities and photoperiods, and clearly show that β-glucosidase is a key enzyme regulating the ABA pool in rose plants.

Influence of air humidity and lighting period on growth, vase life and water relations of 14 rose cultivars

The influence of three relative air humidities (RH) (75, 83 and 91% RH corresponding to vapour pressure deficits of 550, 390 and 200 Pa, respectively) and two lighting periods (18 and 24 h day ˇ1 ) on growth, vase life and leaf‐water relations was studied in 14 rose cultivars. Air humidity had no effect on the number of flowering shoots while shoot fresh weight decreased by 11% as a mean of all cultivars when RH was raised from 83 to 91%. An increase in the lighting period (LP) enhanced the number of flowering shoots by 12% and fresh weight per shoot by 5%. A rise in air humidity from 75 to 91% RH reduced the vase life by 30% (varying from 12 to 75% in the different cultivars) at 18 h LP and by 44% (varying from 31 to 78% in the different cultivars) at 24 h LP, while an increase in LP reduced vase life by 23 and 38% at 75 and 91% RH, respectively. The magnitude of the responses differed significantly among cultivars. Generally, a close relationship was found between reduction in vase life and rate of water loss of detached leaves from all cultivars. It is concluded that high air humidity and continuous lighting in general should be avoided in the production of greenhouse roses. # 1999 Elsevier Science B.V. All rights reserved.

Growing Chlorella sp. on meat processing wastewater for nutrient removal and biomass production

In this work, Chlorella sp. (UM6151) was selected to treat meat processing wastewater for nutrient removal and biomass production. To balance the nutrient profile and improve biomass yield at low cost, an innovative algae cultivation model based on wastewater mixing was developed. The result showed that biomass yield (0.675-1.538 g/L) of algae grown on mixed wastewater was much higher than that on individual wastewater and artificial medium. Wastewater mixing eased the bottleneck for algae growth and contributed to the improved biomass yield. Furthermore, in mixed wastewater with sufficient nitrogen, ammonia nitrogen removal efficiencies (68.75-90.38%) and total nitrogen removal efficiencies (30.06-50.94%) were improved. Wastewater mixing also promoted the synthesis of protein in algal cells. Protein content of algae growing on mixed wastewater reached 60.87-68.65%, which is much higher than that of traditional protein source. Algae cultivation model based on wastewater mixing is an efficient and economical way to improve biomass yield.

A high proportion of blue light increases the photosynthesis capacity and leaf formation rate of Rosa × hybrida but does not affect time to flower opening

Alterations in light quality affect plant morphogenesis and photosynthetic responses but the effects vary significantly between species. Roses exhibit an irradiance-dependent flowering control but knowledge on light quality responses is scarce. In this study we analyzed, the responses in morphology, photosynthesis and flowering of Rosa × hybrida to different blue (B) light proportions provided by light-emitting diodes (LED, high B 20%) and high pressure sodium (HPS, low B 5%) lamps. There was a strong morphological and growth effect of the light sources but no significant difference in total dry matter production and flowering. HPS-grown plants had significantly higher leaf area and plant height, yet a higher dry weight proportion was allocated to leaves than stems under LED. LED plants showed 20% higher photosynthetic capacity (Amax ) and higher levels of soluble carbohydrates. The increase in Amax correlated with an increase in leaf mass per unit leaf area, higher stomata conductance and CO2 exchange, total chlorophyll (Chl) content per area and Chl a/b ratio. LED-grown leaves also displayed a more sun-type leaf anatomy with more and longer palisade cells and a higher stomata frequency. Although floral initiation occurred at a higher leaf number in LED, the time to open flowers was the same under both light conditions. Thereby the study shows that a higher portion of B light is efficient in increasing photosynthesis performance per unit leaf area, enhancing growth and morphological changes in roses but does not affect the total Dry Matter (DM) production or time to open flower.

Effects of air humidity and K/Ca ratio in the nutrient supply on growth and postharvest characteristics of cut roses

Single node cuttings with one mature leaf were taken from the rose cv. Baroness and rooted in water culture. The rooted plants were grown in nutrient solutions and subjected to two levels of relative air humidity (RH): high (90%) and moderate (70%), in combination with high (12/1), medium (1/1) and low (1/5) K/Ca ratios in the nutrient solution. High RH plants accumulated less Ca in leaves and flowers than moderate RH plants. Roses grown at moderate RH had a longer postharvest life than high RH roses, irrespective of the K/Ca ratio of the nutrient solution. In general, a high K/Ca ratio had a negative impact on postharvest life. When grown at a high K/Ca ratio the ornamental value declined rapidly, mainly due to the appearance of necrotic petals as well as chlorotic and necrotic areas on the leaves. Bent neck occurred only with high RH plants but changes in the K/Ca ratio had no differential effect. Dry spots and brittle leaves were observed on high RH roses, and the occurrence increased with increased K/Ca ratio in the nutrient solution. Stomatal conductance increased in parallel with increases in RH and K/Ca ratio when measured on intact roses placed in dry air (40% RH).

Keeping quality of cut roses as affected by high supplementary irradiation

Abstract The rose cultivars ‘Kiss’, ‘Frisco’, ‘Cardinal’, ‘Madelon’ and ‘Jaguar’ were grown in a greenhouse under four different levels of supplementary irradiance (130, 190, 250 and 370 μmol m−2 s−1) applied for 20 h day−1. Five times during the production period roses were harvested for the purpose of testing the keeping quality. Vase life and number of days till occurrence of bent neck was about 30% higher when the roses were harvested in June than when they were harvested in November and January. Vase life increased when the supplementary irradiance level increased from 130 to 370 μmol m−2 s−1. The increase in vase life with increase in radiation was most pronounced for ‘Cardinal’ and ‘Madelon’. Significant cultivar differences in vase life and days to leaf drop and bent neck were observed, ‘Madelon’ had the longest vase life.

Water uptake of cuttings and stem pieces as affected by different anaerobic conditions in the rooting medium

Abstract Water uptake is critical for the successful rooting of cuttings. Substrates are therefore saturated with water and anoxic conditions may develop due to the consumption of oxygen. The effects of gaseous nitrogen and carbon dioxide on water uptake were compared with that of air in experiments with Euphorbia, Begonia and Pelargonium cuttings. Wilting and other symptoms encountered in Euphorbia propagation occurred under anaerobic conditions. Water uptake compared with air injection was reduced, more by carbon dioxide injection than by nitrogen. Water uptake in Begonia cuttings was also more reduced in carbon dioxide than in nitrogen. Water uptake of Pelargonium cuttings was not affected by either carbon dioxide or nitrogen. The different sensitivity of cuttings to different gasses in the substrate is discussed in view of differences in their rooting ability.

Determination of UV action spectra affecting the infection process of Oidium neolycopersici, the cause of tomato powdery mildew

Oidium neolycopersici, the cause of powdery mildew in tomato, was exposed to UV radiation from 250 to 400 nm for 1, 12, or 24 min. Radiation ≤ 280 nm strongly reduced conidial germination, hyphal expansion, penetration attempt and infection of O. neolycopersici. From 290 to 310 nm the effect depended on duration of exposure, while there was no effect ≥ 310 nm. There were no significant differences within the effective UV range (250-280 nm). Conidial germination on a water agar surface was <20% or around 40%, respectively, if samples were exposed for 1 min within the effective UV range followed by 24h or 48 h incubation. Twelve or 24 min exposure reduced germination to close to nil. A similar trend occurred for germination of conidia on leaf disks on water agar in Petri dishes. The effective UV range significantly reduced all subsequent developmental stages of O. neolycopersici. There was no cytoplasmic mitochondrial streaming in conidia exposed to the effective UV range, indicating that there may be a direct effect via cell cycle arrest. There was no indication of reactive oxygen species involvement in UV mediated inhibition of O. neolycopersici. Optical properties of O. neolycopersici indicated that the relative absorption of UV was high within the range of 250 to 320 nm, and very low within the range of 340 to 400 nm. Identification of UV wavelengths effective against O. neolycopersici provides a future basis for precise disease control.

The effect on growth of Chlamydomonas reinhardtii of flue gas from a power plant based on waste combustion

Flue gases from a power plant based on waste combustion were tested as a carbon dioxide (CO2) source for growing Chlamydomonas reinhardtii. To achieve recognition as an environmentally friendly hydrogen production method, waste gases should be used to grow this hydrogen-producing microalgae. The algae were grown in undiluted flue gas containing 11.4±0.2% CO2 by volume, in diluted flue gas containing 6.7±0.1% or 2.5±0.0% CO2, and in pure liquid CO2 at a concentration of 2.7±0.2%. The NOx concentration was 45±16 mg m-3, the SO2 concentration was 36±19 mg m-3, the HCl concentration 4.1±1.0 mg m-3 and the O2 concentration 7.9±0.2% in the undiluted flue gas. Undiluted flue gas reduced the dry weight production by around 20-25% when grown at a photon flux density (PFD) of 300 μmol m-2 s-1 artificial light and at 24 or 33°C, compared with the other treatments. A less negative effect was found at the highest flue gas concentration when the algae were grown at 75 μmol m-2 s-1 PFD. Growing the algae outdoors at a day length of 12.5 h and a temperature of around 24°C, the dry weight production was higher (about 15%) in the 2.6% CO2 flue gas treatment compared with all other treatments. Reducing the light level by 30% through shading did not affect the dry weight production. Calculated on aerial basis the productivity reached approximately 70 g m-2 day-1 in the 300 μmol m-2 s-1 PFD treatment (corresponding to 25 mol m-2 day-1) and approximately 17 g m-2 day-1 in the 75μmol m-2 s-1 PFD treatment (corresponding to 6.5 mol m-2 day-1). The outdoor production reached around 14 g m-2 day-1. It was concluded that the negative effect of the undiluted flue gas was attributable to the high CO2 concentration and not to the other pollutants.