Interaction of photoperiod and temperature in flowering-control of Gypsophila paniculata L

Long day promotes flowering of Gysophila paniculata L cultivar ‘Bristol Fairy’. Repeated treatments with GA₃ or GA_{4 + 7} in short days did not promote flowering. The long photoperiod is effective only at relatively high temperatures. At night temperatures below 12°C, the plants remain vegetative even in long days. Efficient artificial lighting is from incandescent lamps at 60–100 lux. Fluorescent lighting (Cool-White) is not effective. Lighting of 4 hours as a night-break or at the end of the night were equally effective, but 4 hours lighting as a day-extension was less effective. Whole-night lighting promoted flowering more than any of the 4-hour lighting regimes. Cyclic lighting of one third light in each cycle promoted flowering to the same extent as continuous lighting. Light intensity during the day has a decisive effect on flower production.     

Moving lamps increase leaf photosynthetic capacity but not the growth of potted gerbera

To investigate the responses of leaf photosynthesis and plant growth to a moving lighting system, potted gerberas (Gerbera jamesonii H. Bolus ex J.D. Hook “Festival”) were grown under supplemental lighting in a greenhouse with either a stationary or a moving lighting system positioned above the benches. The stationary system consisted of a fixed high pressure sodium (HPS) lighting system, while the moving lighting system consisted of a moving HPS fixture attached to a cable system to move the light fixture back and forth over the crop. In both cases, the supplemental lighting was applied from 6:00 to 24:00 h with the same supplemental daily light integral (4.9 mol m⁻² day⁻¹). Moving lamps significantly increased leaf photosynthetic capacity as represented by light saturated net CO₂ exchange rate (NCER) (A_sat), light- and CO₂-saturated rate of NCER (A_max), maximum rate of Rubisco carboxylation (V_cmax), maximum rate of electron transport (J_max) and rate of triose phosphate utilization. However, in situ leaf NCER and stomatal conductance, leaf chlorophyll content index, leaf area, leaf thickness, fresh weight of plants were significantly lower under moving lighting than under stationary lighting. It is suggested that the reduced growth of plants under moving lighting might be due to (1) the overall lower light use efficiency of leaves under moving lighting than those under stationary lighting; (2) the slower response time of the photosynthetic system compared to the rate of change in light intensity under moving lighting.     

LED光质补光对黄瓜幼苗生长和光合特性的影响

采用发光二极管（light emitting diode,LED）精确调制光谱能量分布,以单色光质（红光、蓝光、UV-B）和组合光质（红/蓝1∶1）进行每天4 h补光,以未补光组为对照,研究LED光质补光对黄瓜幼苗生长和光合特性的影响。结果表明：与未补光组相比,LED光质补光处理显著促进了黄瓜幼苗的生长;不同光质对黄瓜幼苗生长和光合特性的影响具有一定的差异性。其中,UV-B处理显著提高了黄瓜幼苗叶片单位鲜质量的叶绿素a、叶绿素b和类胡萝卜素含量,但显著降低了Fv/Fm;红光处理显著提高了黄瓜幼苗的真叶数、叶面积、株高、干鲜质量、壮苗指数、根系活力、SOD活性和可溶性蛋白含量。总体而言,红光有利于培育壮苗,较适合作为黄瓜育苗的补光光质。     

冬季温室延长光照时间对‘西州密25号’生长发育的影响

为了明确延长光照时间对厚皮甜瓜生长发育的影响,采用光通量密度为72μmol·m^-2·s^-1的人工光源对‘西州密25号’甜瓜植株进行不同时长的补光,研究了不同光照时间对甜瓜植株高度、茎粗度、叶片、节间长度、叶柄长度、叶绿素、保护酶、可溶性糖、果实的影响。结果表明延长光照时间有利于增加甜瓜植株高度、叶面积、茎粗度、节间长度、叶柄长度,提高其干物质的含量、根冠比、叶绿素含量,有利于保护酶POD、CAT活性的增加,促使可溶性糖含量减少,单果质量、可溶性固形物含量、果肉厚度增加,对果形指数影响不显著。延长光照时长4 h以上有利于‘西州密25号’植株的生长,延长光照8h‘西州密25号’果实单果质量可达380.83g,果实中可溶性固形物含量达到16.2%。     

Cost-efficient light control for production of two campanula species

A cost-efficient light control system based on weather forecasts, electricity prices and daily photosynthesis integral (DPI) was evaluated for application in the commercial production of the long-day (LD) plant Campanula portenschlagiana ‘Blue Get Mee’ and C. cochlearifolia ‘Blue Wonder’. Experiments were conducted under both autumn and spring conditions and included four treatments. Three treatments were controlled by the software system DynaLight Desktop which automatically defined the most cost-efficient use of supplemental light, -based on a predefined set point of DPI, forecasted solar irradiance and the market price on electricity. The set points of DPI in the three treatments were 300, 450 and 600 mmol CO₂ m⁻² leaf d⁻¹ and the treatments were compared with a traditional LD 19-h treatment. The DPI-based light control strategy resulted in very irregular light patterns including daily periods of solar irradiance combined with supplemental light in low light periods and a night period interrupted by irregular light breaks (NB-lighting). Both campanula species flowered in the DPI-based treatments during spring, but the flowering percentage was low and non-uniform during autumn. This was caused by a combination of the irregular light, low natural light intensities and a decrease in daily light integral (DLI), and could be restored by maintaining a continuous 19 h photoperiod with incandescent lamps (<5 μmol m⁻² s⁻¹), illustrating that photoperiod was an important factor for flowering in LD species grown under low light intensities. Growth in terms of carbon gain was marginally affected by the irregular light and a 25% reduction in electricity costs was achieved without major reductions in plant quality in spring. Our results illustrate that plant production of LD species can be maintained in a cost-efficient light control system where the use of supplemental light is based on weather forecasts and electricity prices.     

Effect of photoperiod and light integral on flowering and growth of Eustoma grandiflorum (Raf.) Shinn.

The aim of the study was to examine the effects of different photoperiod and light integral on floral initiation, development and subsequent growth of Eustoma grandiflorum (Raf.) Shinn. Six-weeks-old seedlings of ‘Echo Blue’ and ‘Fuji Deep Blue’ were placed under short day (SD, 10 h) and were transferred to long days (LD, 20 h) at 2-week intervals from 6 to 14 weeks after seeding. Plants initiated flower buds regardless of light regimes. Flower bud initiation was delayed by SD compared to LD; plants transferred after 6 weeks from seeding initiated flower buds at least 21 and 10 days earlier at LD at high (HL) and low (LL) daily light integral, respectively, compared to those at SD. Light regimes had little or no effect on time to flower bud development after initiation. Thus, it seems likely that LD and HL affected the initiation rather than development. Both the photoperiod and light integral strongly influenced the subsequent growth after initiation. SD delayed the time to visible bud (VB), increased the number of nodes to first open flower, number of branches, stem diameter and shoot dry weight compared to LD. HL promoted flowering and increased several shoot characteristics and flowering compared to LL.The results indicate that Eustoma is a quantitative long-day plant. LD, and more specifically HL, enhanced flower bud initiation, development and subsequent growth. An initial SD period is preferred to increase the number of branches, number of flowering buds and flowers, stem diameter and shoot dry weight.     

The effect of intracanopy lighting on cucumber fruit yield—Model analysis

Intracanopy lighting is a recently developed supplementary lighting technique for high-wire grown vegetable production in greenhouses where a part of the lamps is mounted within instead of above the canopy. A potentially higher yield using intracanopy lighting compared with top-lighting, is based on three assumptions: (1) increased light-absorption by the crop; (2) a higher photosynthetic light use efficiency due to a more homogeneous vertical light distribution; (3) a preserved photosynthetic capacity of leaves deeper in the canopy. We used an explanatory crop model to quantify the relative importance of these assumptions for a cucumber crop during an experiment in winter in the Netherlands (Trouwborst et al., 2010). Photosynthesis and yield data of this intracanopy lighting experiment with light-emitting diodes (34% of supplemental PAR) in combination with top-lighting (66% of supplemental PAR) were used to parameterise our model. In that study intracanopy lighting did not result in an increased yield compared with 100% top-lighting due to extreme leaf curling and a lower dry matter partitioning to the fruits. Our model predicted an 8% increase in fruit yield for the intracanopy lighting treatment if there were to be no leaf curling and no lower dry matter partitioning. This increase can be largely explained by the change in light distribution and light absorption. The model further revealed unexpectedly large consequences of the lower dry matter partitioning to the fruits whereas the negative effect of leaf curling was small. The direct effect of a greater A_max at deeper canopy layers was slightly positive. The last however might have indirectly caused the greater partitioning to the leaves as the greater A_max was associated with a preserved leaf mass per area. Solutions for this problem are discussed. Our explanatory model allowed us to disentangle the interacting effects of intracanopy lighting on fruit yield. Overall, intracanopy lighting has been shown here to potentially increase the assimilation light use efficiency.     

Response of pepper and eggplant to continuous light in relation to leaf chlorosis and activities of antioxidative enzymes

Activities of the oxygen radical-scavenging enzymes were determined in leaves of ‘Kyomidori’ pepper (Capsicum annuum L.) and ‘Senryo’ eggplant (Solanum melongena L.) seedlings under two photoperiod treatments; 12 h light/12 h dark (12/12 h) or with continuous light (24/0 h) for six days. Growing eggplant under continuous light resulted in leaf chlorosis after four days and a sharp decline in the chlorophyll content. In eggplants grown under 24/0 h photoperiod, the activities of antioxidative enzymes; superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) rapidly increased from day two. This was an indication of photooxidative damage. In contrast, leaf chlorosis did not occur in pepper plants grown under continuous light, while the chlorophyll content was even higher in the 24/0 h than in the 12/12 h photoperiod. Continuous light did not enhance the activities of SOD and POD in leaves of pepper. However, the CAT activity increased faster and was significantly higher in pepper than in eggplants grown under continuous illumination. Pepper plants did not appear to suffer from photooxidative damage and thus grew normally under continuous illumination.     

Responses of four hornet species to levels of urban greenness in Nagoya city,Japan: Implications for ecosystem disservices of urban green spaces

Although there is a common trend towards increasing green space in modern cities, urban green spaces provide not only ecosystem services but also disservices for urban dwellers. However, the relationship between urban greenness and ecosystem disservices has been poorly examined. We aimed to understand the effect of greenness level on the abundance and species composition of hornets – critical pests in Japan and to identify the best spatial scale for estimating their abundance with reference to greenness levels. We used a dataset that contained eight years of abundance data for four hornet species at 11 sites in Nagoya city. The levels of greenness around the hornet sampling points were measured using averages from the Normalized Difference Vegetation Index (NDVI) with radiuses of 0.1–10.0 km. We analysed the relationship between abundance and species composition of hornets and NDVI at different spatial scales using generalized linear mixed models. Higher NDVI values positively affected the abundance of all the hornet species except Vespa analis. The abundances were estimated most effectively using the NDVI average with a 1–2 km radius for all species. The species composition of hornets drastically changed along the gradient of NDVI values; V. mandarinia was dominant in greener areas (over 0.2–0.3 NDVI average with a 2 km radius) and V. analis in less green areas (below 0.2–0.3 NDVI average). Our study showed that the abundance and species composition of hornets were both strongly associated with the level of urban greenness. This suggests that increases in the greenness of urban areas can increase hornet abundance and alter the species composition of hornets; a more aggressive species, V. mandarinia, may also increase in urban areas, although V. analis is currently the most critical species according to regional consultants. Balancing ecosystem services and disservices has become crucial for the planning and management of green spaces, particularly when urban green space increases. We also demonstrate how human tolerance towards wildlife may have to be improved in order to live in greener environment where wildlife can be expected.     

不同光质补光对黄瓜、辣椒和番茄幼苗生长及生理特性的影响

 采用新型半导体光源精确调制光质(红光、黄光、绿光、红蓝组合光和蓝光),对大棚内的黄瓜‘中农21’和‘中农27’,辣椒‘巨无霸5号’和‘镇研六号’,番茄‘荷兰红粉’和‘以色列虹丰’进行定时补光。研究结果表明,不同光质补光对3种蔬菜共6个品种幼苗生长影响显著且存在差异,总体认为,补充红光和红蓝光使幼苗茎粗、鲜样质量和干样质量以及壮苗指数均显著高于对照（无补光处理）,黄瓜‘中农21’、番茄和辣椒的可溶性糖含量也显著提高。在蓝光处理下,辣椒‘巨无霸5号’壮苗指数和干样质量均达到最大且显著高于对照。红光或黄光显著提高黄瓜、番茄‘以色列虹丰’的叶绿素和类胡萝卜素含量。     

Effects of intracanopy lighting on photosynthetic characteristics in cucumber

Plants of cucumber (Cucumis sativus L. cv. Euphorbia) were grown in a traditional high-wire cultivation system to investigate the effects of three lighting regimes on photosynthetic characteristics, leaf area and yield. The lighting regimes included overhead lighting (OH), where all the lamps were mounted above the canopy and overhead + intracanopy lighting (OH + IC) which comprised 65% of overhead lamps and 35% of lamps mounted vertically along the plant rows. All overhead lighting was provided for 20 h day⁻¹ and intracanopy lighting was provided for either 20 h or 24 h day⁻¹ lighting period. Intracanopy lighting improved the light distribution in the canopy. Gas exchange measurements showed that intracanopy lighting increased net photosynthesis (P_N) and photosynthetic capacity (P_max). Parameters calculated from CO₂ response (A/C_i) curves showed that in vivo estimate of the maximum rate of Rubisco carboxylation (Vc_max) and the maximum rate of electron transport (J_max) were affected by light regime. Intracanopy light increased yield by 11% compared to traditional overhead light.     

Bulbing responses of two cultivars of red tropical onions to photoperiod,light integral and temperature under controlled growth conditions

Summary

The effects of photoperiod, light intensity and temperature on bulb formation and bulb structure of two tropical onion cultivars were investigated. From an initial experiment it was observed that the number of true scales and sheath scales differed significantly between the cultivars ‘Red Creole’ and ‘Agrifound Dark Red’. When these two cultivars were given 11, 12 and 13 h photoperiod treatments, it was found that both cultivars needed at least 12 h photoperiod for bulb formation. Modify the R/FR ratio from 1.22 to 1.16 in the final hour of the 11 h light period did not induce bulbing. The 13 h photoperiod increased the number of true scales and decreased the number of sheath scales compared with the 12 h photoperiod in both cultivars but total scale + leaf sheath numbers remained nearly constant. When onion plants were grown under 0%, 25%, 50% and 75% shading treatments, (12 h photoperiod), only plants receiving 0% and 25% shading bulbed. Low light intensity decreased the number of true scales and increased the number of sheath scales. Four temperature regimes were compared in a growth room experiment. Plants under the 29°348C treatment bulbed within two weeks and matured within six weeks. However, plants receiving the 25°308C treatment delayed bulb initiation more than those plants receiving 17°228C and 21°268C treatments. At the lowest temperature, bigger bulbs with thick necks were produced. This may be due to changes in bulb structure since at low temperature, the number of sheath scales was increased, however the number of true scales remained relatively constant in both cultivars. Dormant leaf initials decreased with decreasing temperature while the number of secondary meristems significantly increased. The results suggest that ‘Red Creole’ was more responsive to shorter photoperiods, bulbing earlier than ‘Agrifound Dark Red’. There was no significant difference in time to bulbing in response to temperature between the two cultivars if measured by bulbing ratio however there were differences in bulb structure which suggested that ‘Red Creole’ bulbed earlier. These effects may be due to the breeding histories of the two cultivars. It is suggested that studying bulb structure may provide a useful method of interpreting onion bulbing responses.     

Promotion of flowering by photoperiodic lighting in winter-grown gladiolus planted at high densities

Gladiolus plants were grown in winter and early spring at several densities, under natural day, or long day (LD) regimes, with low intensity light at night. LD treatment promoted flowering-percentage (by reducing “blindness”), and enhanced flower quality features, (length of stem and spike, and number of florets per spike). The effect was observed even at planting-densities of 2–3 times the normal winter density. Lighting for 1 hour at mid-night was effective, but the greatest effect was observed by lighting throughout the night. Most of the promotive effects were obtained by lighting for 4 hours as day extension or as night break, and this treatment was recommended for commercial use. Cyclic lighting of 5 minutes of light and 10 minutes of dark was as effective as continuous light for 4 hours, and light intensity of 35 lux was as effective as 130 lux.All cultivars of gladiolus grandiflorus tested responded to the LD treatment, but the miniature cultivar ‘Charm’ did not. The LD effect was especially pronounced under conditions when the normal flowering was defective, such as with high-density plantings, low temperatures and with summer cultivars.     

Effects of far-red light/temperature DIF and far-red light/temperature pulse combinations on height of lily hybrids

Summary

Potted bulbs of ‘Nellie White’, ‘Sunray’ and ‘Stargazer’ representing three lily hybrids [Easter (Lilium longiflorum Thunb.), Asiatic and Oriental, respectively], were forced in a glass greenhouse under three lighting regimes namely, 8.h photoperiod (8 PP) by using blackout between 1600 hours and 0800 hours to eliminate twilight; 8 PP extended with 1.h of low intensity far-red radiation (9 PP) at the beginning of the dark period; or ambient. All three lighting regimes were in a greenhouse with either a +5°C or a -5°c DIF (= T_day ±T night ) regime, while maintaining the same 24.h temperature. In a second experiment, two cultivars of each of the three lily hybrids were also grown under the same three lighting regimes with a constant day/night temperature but with either a 15°cor 25°c pulse for 3.h from 1500–1800.hours to coincide with the far-red supplementation for 9 PP. Both experiments were done during the winter and repeated the following year. Within each DIF treatment, plants which received light containing far-red at the end and start of the day (ambient) or beginning of night (9 PP) were taller than those under short day (8 PP). Plants grown under either 8 PP or ambient were taller under +DIF than under -DIF, except when 8 PP was extended with 1.h of far-red, in which case plant height was the same for either DIF. ‘Nellie White’ reacted the strongest to far-red as well as to DIF followed by ‘Sunray’ and then ‘Stargazer’. For ‘Nellie White’, the stem dry weight was increased by far-red radiation at the beginning of the dark period compared with short day or ambient, while the opposite was found for the leaf and bulb dry weights. However, total dry weight of plant was not affected by either DIF or lighting treatment. In the second experiment, plant height was not significantly affected by an end of day temperature pulse of -5°c for either the 9 PP or ambient regimes compared with a +5°c pulse.     

Effects of nitrogen availability and supplementary light on the nitrate content of soil-grown lettuce

Summary

The effect of nitrogen availability and low level supplementary light on the growth and nitrate content of butterhead lettuce (Lactuca sativa var. capitata L.) grown in soil under greenhouse conditions in winter was studied. No significant interactions between nitrogen availability and supplementary light on yield, nitrate content, osmotic potential of expressed leaf sap and component osmotica were found. Supplementary light greatly increased plant growth and resulted in earlier harvest. When harvested with similar fresh weights, plant nitrate content was significantly reduced by supplementary light although the effect was slight. The reduced contribution of nitrate to sap osmotic potential at the higher light level was accompanied by a significant increase in the contribution of sucrose. While plant fresh weight was unaffected by the rate of nitrogen application, a positive correlation between nitrate content and nitrogen application rate was found. Reduced nitrate content at low nitrogen application rates was accompanied by increased contributions of chloride, glucose and sucrose to sap osmotic potential.     

Effects of photoperiod on shoot elongation and endogenous gibberellins in the glasshouse carnation

Plants of glasshouse carnation were grown in photoperiodic cycles comprising 8 h natural daylight followed by either 16 h of darkness (short-day treatment) or by 16 h of low-intensity lighting from tungsten filament lamps (continuous-light treatment). When plants were transferred from short days to the continuous-light treatment, rates of shoot elongation were increased and flower initiation was promoted. Shoot tips of plants grown in continuous light yielded greater amounts of diffusible gibberellin-like substances than shoot tips of plants grown in short days. Yields of diffusible gibberellins increased with increases in the duration of the continuous light treatment up to 28 days, by which time flower initials were present. Application of GA₃ to the plants resulted in increased rates of shoot elongation, but no effect on flowering was observed.     

The response of plant growth and leaf gas exchange to the speed of lamp movement in a greenhouse

High-pressure sodium (HPS) light supplementation during the low-light months has become quite common for high-light requiring crops at latitudes above 45°. Most common systems have fixed installations, while movable systems have been tried with various results in greenhouses. The concept is that fewer lamps are used on a track system, and that light intensity varies over time. In two trials, we determined whether the speed of the HPS lamp movement had any effect on leaf CO₂ exchange rate, growth and developments of various plants species. Plants (chrysanthemum, petunia, rose and tomato) were grown in a greenhouse supplemented with HPS lamps which moved at various speeds (0, 2, 8 and 20 mm s⁻¹) between 06:00 and 24:00 h daily for about 6–7 weeks. One trial started at the end of November and one started at the end of January. The light sum from the lamps were 0.212 ± 0.004 mol m⁻² h⁻¹ at bench level, and the supplemental lighting represented 55 and 35% of the total light received by the plants for the two trial dates, respectively. The growth (dry matter) was reduced for tomato only when grown under moving lights compared to those grown under the stationary system, while plant height was not affected. Light saturated CO₂ exchange rate on the youngest fully developed leaves increased with lamp speed for petunia and tomato, but not for chrysanthemums, while apparent quantum yield was not affected by lamp speed for any species. In situ measurements of net CO₂ exchange rate (NCER) with supplemental lighting only, showed that NCER decreased exponentially when lamp speed increased from 0 to 20 mm s⁻¹.     

不同补光强度对冬季温室茄子生长的影响

研究了HMZ40型植物补光灯不同补光强度对冬季温室茄子生长的影响。试验结果表明,冬季温室补光促进了茄子的光合作用,茄子体内的叶绿素含量、净光合速率、胞间CO2浓度、气孔导度均随着光照强度的增加而显著增加;增加了茄子植株的长势,促进了果实的发育,随着光照强度的增加,株高、茎粗、叶面积的相对生长量显著增加,坐果率、果实纵径与横径的生长速度均显著增加。     

Nitrogen and irradiance levels affecting net photosynthesis and growth of young coffee plants (Coffea arabica L.)

Summary

Shoot growth attributes, leaf anatomical changes and net photosynthetic rates were determined in young coffee plants fertilized at high and low levels and subjected to shade or full sunlight. High nitrogen supply increased plant height irrespective of the light level imposed during growth, and promoted a larger leaf area in plants of the shade treatment. Specific leaf weight was 15% higher in plants grown in full sunlight than in shaded plants, at both nitrogen levels. The number of leaves developed on the orthotropic stem increased significantly under full irradiance and high nitrogen availability. Leaves were 11% thicker ih unshaded plants than in shaded ones, because of the increased size of the palisade and spongy parenchyma tissues. More thylakoids per granum and more grana per chloroplast were observed in shade-grown plants, mainly in those given high nitrogen treatment. Total nitrogen content expressed on a leaf-area basis was higher in sun plants supplemented with nitrogen, whereas chlorophyll a and b and protochlorophyll contents increased in shade-grown plants. Net photosynthetic rate in high nitrogen plants reached 7.19 µmol CO₂ m^?2 s^?1 in the full irradiance treatment, and 5.46 µmol CO₂ m^?2 s^?1 in shaded plants. Maximum net photosynthetic rates in the low nitrogen plants were 5.28 and 4.90 µmol CO₂ m^?2 s^?1 in sun and shade plants, respectively. Increased photosynthetic light saturation was observed in high irradiance plants (628 µmol m^?2 s^?1) relative to shade plants (359 µmol m^?2 s^?1) in the high nitrogen treatment. The same pattern was observed in low nitrogen plants. The apparent quantum yield of shade acclimated plants was 14% higher than in those grown in full sunlight. Our results indicate that coffee may be classified as a facultative shade species, exhibiting features of sun adapted plants coupled with shade acclimation attributes, this fairly high adaptive capacity to shade:sun transition being strongly influenced by the level of nitrogen nutrition given to the plants.     

Does time spent on visits to green space mediate the associations between the level of residential greenness and mental health?

ObjectiveThe objective of the current study was to explore whether time spent visiting green space near home acts as a mediator in the association between level of residential greenness and perceived mental health.MethodsQuestionnaire data and satellite data of residential greenness were gathered in four European cities (total n = 3748): Barcelona (SP), Doetinchem (NL), Kaunas (LT) and Stoke-on-Trent (UK).ResultsMediation analyses showed that time spent visiting green space near home was a weak, but statistically significant, mediator in the pooled data and in the Dutch sample only.ConclusionsThe findings provide little support for the hypothesis that purposeful visits are a mediator linking indirectly greenness with mental health. More research is needed to explore other mediators related to different exposure pathways, such as visual exposure, and alternative mechanisms, such as (perceived) safety.