Environmental conditions affect pectin solubilization in cherry tomato fruits grown in two experimental Mediterranean greenhouses

Considering the economic importance of the tomato and its nutritional benefits for human health, we studied how different environmental factors [temperature, solar radiation and vapour–pressure deficit (VPD)] influenced the pectin solubilization and the calcium concentration in cherry tomato fruits (Solanum lycopersicum cv. Naomi) grown in two experimental greenhouses: improved parral type (low-technology) and multispan type (high-technology). For three years (2004, 2005 and 2006), three fruit samples were taken over the entire production period: at the beginning of harvest [16 weeks after transplanting (WAT)], at mid-harvest (26 WAT), and at the end of harvest (35 WAT). Values for temperature, solar radiation, and VPD peaked in the third sampling in both greenhouses during the three years, being higher in the parral greenhouse during the production cycle. No-market production and peroxidation indicators [measured as H₂O₂ and malondialdehyde (MDA) concentrations] significantly increased at the end of the productive period in both greenhouses, indicating the presence of oxidative stress caused by the rise in temperature, solar radiation, and VPD, which was more pronounced in the parral greenhouse. Water-soluble pectins, pectate, and protopectin contents were measured, revealing an increase in the former two and a reduction in the latter under environmental stress. This indicates a clear pectin solubilization in cherry tomato fruit. The enzymes pectolytic polyglacturonase (PG), pectin methylesterase (PME), and pectate lyase (PEL), altered their activities during the third sampling, while the calcium concentration fell drastically. Therefore, both the increase in pectin solubilization as well as the reduction in the Ca concentration during harshest environmental stress in the third sampling, especially in the parral greenhouse, could degenerate the textural properties of the cherry tomato, reducing its quality and consumer acceptance.     

Two minuses can make a plus: waterlogging and elevated CO2 interactions in sweet cherry (Prunus avium) cultivars

The increase in the ambient concentration of CO₂ and other greenhouse gases is producing climate events that can compromise crop survival. However, high CO₂ concentrations are sometimes able to mitigate certain stresses such as salinity or drought. In this experiment, the effects of waterlogging and CO₂ are studied in combination to elucidate the eventual response in sweet cherry trees. For this purpose, four sweet cherry cultivars (‘Burlat’, ‘Cashmere’, ‘Lapins and ‘New Star’) were grafted on a typically hypoxia‐tolerant rootstock (Mariana 2624) and submitted to waterlogging for 7 days at either ambient CO₂ concentration (400 µmol mol^?1) or at elevated CO₂ (800 µmol mol^?1). Waterlogging affected plants drastically, by decreasing photosynthesis, stomatal conductance, transpiration, chlorophyll fluorescence and growth. It also brought about the accumulation of proline, chloride and sulfate. Nonetheless, raising the CO₂ supply not only mitigated all these effects but also induced the accumulation of soluble sugars and starch in the leaf. Therefore, sweet cherry plants submitted to waterlogging were able to overcome this stress when grown in a CO₂‐enriched environment.     

Environmental and economic impacts of solar‐powered integrated greenhouses

Greenhouse vegetable production plays a vital role in providing year‐round fresh vegetables to global markets, achieving higher yields, and using less water than open‐field systems, but at the expense of increased energy demand. This study examines the life cycle environmental and economic impacts of integrating semitransparent organic photovoltaics (OPVs) into greenhouse designs. We employ life cycle assessment to analyze six environmental impacts associated with producing greenhouse‐grown tomatoes in a Solar PoweRed INtegrated Greenhouse (SPRING) compared to conventional greenhouses with and without an adjacent solar photovoltaic array, across three distinct locations. The SPRING design produces significant reductions in environmental impacts, particularly in regions with high solar insolation and electricity‐intensive energy demands. For example, in Arizona, global warming potential values for a conventional, adjacent PV and SPRING greenhouse are found to be 3.71, 2.38, and 2.36 kg CO₂ eq/kg tomato, respectively. Compared to a conventional greenhouse, the SPRING design may increase life cycle environmental burdens in colder regions because the shading effect of OPV increases heating demands. Our analysis shows that SPRING designs must maintain crop yields at levels similar to conventional greenhouses in order to be economically competitive. Assuming consistent crop yields, uncertainty analysis shows average net present cost of production across Arizona to be $3.43, $3.38, and $3.64 per kg of tomato for the conventional, adjacent PV and SPRING system, respectively.     

Effects of elevated CO2 on growth,photosynthesis and respiration of sweet chestnut (Castanea sativa Mill.)

Two year old sweet chestnut seedlings (Castanea sativa Mill) were grown in pots at ambient (350 µmol·mol^–1) and double (700 µmol·mol^–1) atmospheric CO₂ concentration in constantly ventilated greenhouses during entire growing seasons. CO₂ enrichment caused either no significant change or a decrease in shoot response, depending on yearly weather conditions. Similarly, leaf area was either reduced or unchanged under elevated CO₂. However, when grown under controlled conditions in a growth chamber, leaf area was enlarged with elevated CO₂.The CO₂ exchanges of whole plants were measured during the growing season. In elevated CO₂, net photosynthetic rate was maximum in May and then decreased, reaching the level of the control at the end of the season. End of night dark respiration of enriched plants was significantly lower than that of control plants; this difference decreased with time and became negligible in the fall. The original CO₂ level acted instantaneously on the respiration rate: a double concentration in CO₂ decreased the respiration of control plants and a reduced concentration enhanced the respiration of enriched plants. The carbon balance of a chestnut seedling may then be modified in elevated CO₂ by increased carbon inputs and decreased carbon outputs.     

Combined effects of enhanced ultraviolet-B radiation and doubled CO2 concentration on growth, fruit quality and yield of tomato in winter plastic greenhouse

Five different doses of ultraviolet-B (UV-B) radiation were supplied to tomato (Lycopersicon esculeutum. Mill) with the doubled CO₂ concentration (700 μmol · mol⁻¹) in the winter plastic greenhouse. The influences on the seedling growth, fruit quality and yield of tomato were investigated. Results showed that the seedling growth, and the contents of UV absorbing compounds, soluble sugar, organic acid, vitamin C and lycopene of tomato fruits, and yield of tomato increased under doubled CO₂ concentration. Under the doubled CO₂ concentration the effects of lost doses of UV-B radiation could further promote the effects of doubled CO₂ concentration. However, there is no significant increase in yield of tomato. The best dose of UV-B radiation is about 1.163 kJ·m⁻². When the dose of UV-B radiation is more than it, the effects of UV-B will be reduced. __________ Translated from Journal of Wuhan Botanical Research, 2006, 24(1): 49–53 [译自: 武汉植物学研究]     

Carbon and Water Footprints and Energy Use of Greenhouse Tomato Production in Northern Italy

This study reports on the carbon, water, and energy footprints of tomatoes grown in a greenhouse in Northern Italy and two possible future variations of heating and carbon dioxide (CO₂) fertilization on the current setup. The heat supply in place, consisting of natural gas (NG) and canola oil combustion, is compared to cogeneration and incineration of municipal solid waste for heating and CO₂ from industrial exhaust for fertilization. As a benchmark, the current system is also compared to a conventional system, in which heat is delivered solely based on NG. Each kilogram (kg) of fresh tomatoes (“Cuore di Bue” variety) produced in the current greenhouse emits 2.28 kg CO₂ equivalents (eq) and uses 95.5 megajoules (MJ) eq energy and 122 liters (L) of water. Relative to the system in place, the carbon footprint (CF) is 57.5% and 18% higher with conventional NG heating and cogeneration and is 40% lower with waste valorization. Further, 33%, 55%, and 63% less energy and 9%, 96%, and 14% less water are used in the conventional, cogeneration, and waste valorization scenarios, respectively. This confirms that there are multiple strategies to reduce the impact of the tomato production under consideration.     

Photosynthesis and transpiration of tomato and CO2 fluxes in a greenhouse under changing environmental conditions in winter

Responses of tomato leaves in a greenhouse to light and CO₂ were examined at the transient stage at the end of winter, when both photoperiod and irradiance gradually increase. Additionally, CO₂ fluxes were calculated for a greenhouse without supplementary lighting and without CO₂ enrichment based on CO₂ sinks (plant photosynthesis) and CO₂ sources (plant and substrate respiration). In January, tomato leaves in the greenhouse showed low photosynthesis with a maximum assimilation of 6–8 μmol CO₂ m⁻² s⁻¹, a quantum yield of 0.06 μmol CO₂ μmol⁻¹ photosynthetic active radiation (PAR) and a low light compensation point of 26 μmol PAR m⁻² s⁻¹, a combination which classifies them as shade leaves. In February, tomato leaves increased their light compensation point to 39 μmol PAR m⁻² s⁻¹ and quantum yield to 0.08, the former indicating the adaptation to increased irradiance and photoperiod. These tomato leaves increased their transpiration from 0.4 to 0.9 in January to ∼2 mmol H₂O m⁻² s⁻¹ in February. Both photosynthesis and transpiration were primarily limited by light but neither by stomatal conductivity nor by CO₂. In January, light response of photosynthesis, dark respiration and transpiration were negligibly affected by increasing CO₂ concentrations from 600 to 900 ppm CO₂ under low light conditions, indicating no benefit of CO₂ enrichment unless light intensity increased. In February, tomato leaves were photoinhibited at inherent greenhouse CO₂ concentrations on the first sunny day; this photoinhibition was further enhanced by an increased CO₂ concentration of 1000 ppm. CO₂ fluxes in the greenhouse appeared strongly dependent on solar radiation. After exceeding the light compensation point in the morning, greenhouse CO₂ concentrations decreased by 58 or by 110 ppm CO₂ h⁻¹ on a sunny day in January or February and by 23 ppm on overcast days in both months. Calculated per overall tomato canopy, plant photosynthesis contributed 42–50% to the morning CO₂ depletion in the greenhouse. Dark respiration of tomato leaves was ∼2 μmol CO₂ m⁻² s⁻¹ in January and ∼3 μmol CO₂ m⁻² s⁻¹ in February. This dark respiration resulted in rises of 15 and 17 ppm CO₂ h⁻¹ at night in the greenhouse compartment and was identified as primary source of CO₂. Respiration of the substrate used to grow the plants, which produced 7.3 ppm CO₂ h⁻¹, was identified as secondary source of CO₂. The combined plant and substrate respiration resulted in peaks of up to 900 ppm CO₂ in the greenhouse before dawn.     

Incidences and progression of tomato chlorosis virus disease and tomato yellow leaf curl virus disease in tomato under different greenhouse covers in southeast Spain

Epidemics of whitefly‐transmitted Tomato chlorosis virus, Tomato yellow leaf curl Sardinia virus and Tomato yellow leaf curl virus have been present in the south east of Spain since the 1990s. A survey was performed in 40 greenhouses and nethouses during 2003 to establish the relationship between the disease incidence and the quality of greenhouse or nethouse coverings, providing a physical protection of crops against whiteflies. For tomato chlorosis virus disease (ToCD), the incidence correlated with the type of greenhouse cover and was most reduced under higher quality covers. Control of tomato yellow leaf curl disease (TYLCD) was achieved only for crops grown in the highest quality greenhouses. TYLCD incidence in tolerant tomatoes remained below 100% within the 5 months of sampling, despite the disease progress rate at the initial stage of the cultivation being higher than that of ToCD, which did reach 100% incidence in many greenhouses. Linear regression analysis showed that the development of ToCD and TYLCD in most of the greenhouses was best described by the monomolecular model and the Gompertz model, respectively. Tomato infectious chlorosis virus was not detected in parallel surveys carried out during this study, although it has been described previously in the area studied.     

Effect of enriched rhizosphere carbon dioxide on nitrate and ammonium uptake in hydroponically grown tomato plants

Previous reports have indicated positive effects of enriched rhizosphere dissolved inorganic carbon on the growth of salinity-stressed tomato (Lycopersicon esculentum L. Mill. cv. F144) plants. In the present work we tested whether a supply of CO₂ enriched air to the roots of hydroponically grown tomato plants had an effect on nitrogen uptake in these plants. Uptake was followed over periods of 6 to 12 hours and measured as the depletion of nitrogen from the nutrient solution aerated with either ambient or CO₂ enriched air. Enriched rhizosphere CO₂ treatments (5000 μmol mol^-1) increased NO₃ ^- uptake up to 30% at pH 5.8 in hydroponically grown tomato plants compared to control treatments aerated with ambient CO₂ (360 μmol mol^-1). Enriched rhizosphere CO₂ treatments had no effect on NH₃ ⁺ uptake. Acetazolamide, an inhibitor of apoplastic carbonic anhydrase, increased NO₃ ^- uptake in ambient rhizosphere CO₂ treatments, but had no effect on NO₃ ^- uptake in enriched rhizosphere CO₂ treatments. Ethoxyzolamide, an inhibitor of both cytoplasmic and extracellular carbonic anhydrase, decreased NO₃ ^- uptake in ambient rhizosphere CO₂ treatments. In contrast, a CO₂ enriched rhizosphere increased NO₃ ^- uptake with ethoxyzolamide, although not to the same extent as in plants without ethoxyzolamide. It is suggested that a supply of enriched CO₂ to the rhizosphere influenced NO₃ ^- uptake through the formation of increased amounts of HCO₃ ^- in the cytosol. This revised version was published online in June 2006 with corrections to the Cover Date.     

Control of postharvest decay on cherry tomatoes by marine yeast Rhodosporidium paludigenum and calcium chloride

Aims: In this study, the potential of calcium chloride (CaCl₂) application to improve the efficacy of the marine antagonist Rhodosporidium paludigenum in controlling postharvest diseases of cherry tomatoes was assessed. Methods and Results: CaCl₂ alone was found not to have any direct influence on the population growth of R. paludigenum in NYDB cultures or in cherry tomato wounds. However, the combined treatments with 1 × 10⁸ cells ml^?1R. paludigenum and CaCl₂ at the concentration from 0·5 to 2% showed high activities to reduce black rot caused by Alternaria alternata in cherry tomato wounds, significantly higher than those of R. paludigenum or CaCl₂ alone. Meanwhile, 0·5% CaCl₂ in combination with 1 × 10⁸ cells ml^?1R. paludigenum greatly inhibited the natural decay of cherry tomatoes in 21 days’ storage at 25°C. Conclusions: The combination of R. paludigenum and CaCl₂ enhances the inhibition of black rot and natural decay of postharvest cherry tomatoes. The results from this study provide a new way to improve the efficiency of R. paludigenum in maintaining the quality of postharvest fruits and vegetables. Significance and Impact of the Study: The marine yeast R. paludigenum combined with CaCl₂ has greatly potential use as an alternative to chemical fungicides in inhibiting postharvest decay on cherry tomatoes.     

Effects of C02 enrichment on the rates of photosynthesis and translocation of tomato leaves

Effects of C0₂ enrichment on the rates of net photosynthesis (carbon fixation) and translocation (carbon transport) of tomato leaves were examined on a single mature leaf (seventh basal leaf) of plants grown initially under a light flux density of 40 W m^-2 with 350 (control) or 1000 vpm (enriched) CO₂, and then exposed for 6 h to various light flux densities (7, 20, 40 and 130 W m^-2) or CO₂ concentrations (350, 500, 700 and 1000 vpm). When measurements were made in the conditions in which plants were grown, the rates of carbon fixation and carbon transport were 20 and 40% respectively higher in enriched plants than in the control ones. Under conditions different from the growing conditions, the rates of carbon transport in the enriched plants were generally higher than those of the controls with a similar rate of carbon fixation. Leaves grown under a C0₂ enriched environment have a greater constant supply of mobile leaf assimilate than those under atmospheric C0₂. The higher efficiency of carbon transport in enriched plants was apparently retained even when the leaf was temporarily exposed to lower levels of light or CO₂.     

Lower incidence and severity of tomato virus in elevated CO2 is accompanied by modulated plant induced defence in tomato

Elevation in atmospheric CO₂ concentration broadly affects plant phenology and physiology, and these effects may alter the performance of plant viruses. The effects of elevated CO₂ on the susceptibility of tomato plants to Tomato yellow leaf curl virus (TYLCV) were examined for two successive years in open top chambers (OTC) in the field. We experimentally tested the hypothesis that elevated CO₂ would reduce the incidence and severity of TYLCV on tomato by altering plant defence strategies. Our results showed that elevated CO₂ decreased TYLCV disease incidence (by 14.6% in 2009 and 11.8% in 2010) and decreased disease severity (by 20.0% in 2009 and 10.4% in 2010). Elevated CO₂ also decreased the level of TYLCV coat protein in tomato leaves. Regardless of virus infection, elevated CO₂ increased plant height and aboveground biomass. Additionally, elevated CO₂ increased the leaf C:N ratio of tomato, but decreased soluble protein content in leaves. Notably, elevated CO₂ increased the salicylic acid (SA) level in uninfected and infected plants. In contrast, elevated CO₂ reduced jasmonic acid (JA) in uninfected plants while it increased JA and abscisic acid (ABA) in virus‐infected plants. Furthermore, combined exogenous SA and JA application enhanced resistance to TYLCV more than application of either SA or JA alone. Our results suggest that the modulated antagonistic relationship between SA and JA under elevated CO₂ makes a great contribution to increased tomato resistance to TYLCV, and the predicted increases in tomato productivity may be enhanced by reduced plant virus susceptibility under projected rising CO₂ conditions.     

Effect of Elevated CO2 on Photosynthesis and Chlorophyll Fluorescence of Rose Plants Grown at High Temperature and High Photosynthetic Photon Flux Density

Gas exchange and chlorophyll (Chl) fluorescence were measured on young mature leaves of rose plants (Rosa hybrida cvs. First Red and Twingo) grown in two near-to-tight greenhouses, one under control ambient CO₂ concentration, AC (355 µmol mol^–1) and one under CO₂ enrichment, EC (700 µmol mol^–1), during four flushes from late June to early November. Supply of water and mineral elements was non-limiting while temperature was allowed to rise freely during daytime. Leaf diffusive conductance was not significantly reduced at EC but net photosynthetic rate increased by more than 100 %. Although the concentration of total non-structural saccharides was substantially higher in the leaves from the greenhouse with EC, _PS2 (quantum efficiency of radiation use) around noon was not significantly reduced at EC indicating that there was no down-regulation of electron transport. Moreover, CO₂ enrichment did not cause any increase in the risk of photo-damage, as estimated by the 1 – q_P parameter. Non-photochemical quenching was even higher in the greenhouse with EC during the two summer flushes, when temperature and photosynthetic photon flux density (PPFD) were the highest. Hence rose photosynthesis benefits strongly from high concentrations of atmospheric CO₂ at both high and moderate temperatures and PPFD.     

Effects of CO2 and sugars on photosynthesis and composition of avocado leaves grown in vitro

The effects of micropropagation conditions on avocado (Persea americana Mill.) have been measured in leaves and plants cultured in vitro. The consequences of the type and concentration of sugar in the medium and of carbon dioxide concentration in the atmosphere on the rates of photosynthesis and amounts of ribulose 1,5-biphosphate carboxylase-oxygenase (EC 4.1.1.39; Rubisco) and total soluble protein (TSP) were measured. At the highest sucrose supply (87.6 mM), Rubisco content was substantially decreased in leaves, and even more when elevated CO₂ (1 000 μmol·mol⁻¹) was supplied. Maximum photosynthetic rate (P_max) was significantly decreased when plants developed in high sucrose and elevated CO₂. However, Rubisco concentration was significantly greater when glucose was supplied at the same molar concentration or when the concentration of sucrose was small (14.6 mM), and no differences were observed due to the CO₂ concentration in the air in these treatments. The ratio of Rubisco to total soluble protein (Rubisco/TSP) was dramatically decreased in plants grown in the highest concentration of sucrose and with elevated CO₂. Leaf area and ratio of leaf fresh weight/(stem + root) fresh weight, were greater in plants grown with CO₂ enriched air. However, upon transplanting, survival was poorer in plants grown on low sucrose/high CO₂ compared to those grown on high sucrose/high CO₂.     

Effect of CO2-Concentration on the Accumulation of Starch and Sugar in Tomato Leaves

The carbohydrate content (starch, glucose and sucrose) in tomato plants grown in air Containing 0.04, 0.10, 0.15, 0.22, 0.32, or 0.50 vol. per cent CO₂ was studied at 2 hours’ intervals over a period of 24 hours. The highest starch content was found at 0.22 vol. per cent CO₂, while the highest content of soluble sugars were reached at a concentration of 0.10 vol. per cent CO₂. A few observations of the morphogenic effects of carbon dioxide were also made.     

Population suppression of Bemisia tabaci (Hemiptera: Aleyrodidae) using yellow sticky traps and Eretmocerus nr. rajasthanicus (Hymenoptera: Aphelinidae) on tomato plants in greenhouses

We conducted three experiments for management of Bemisia tabaci (Gennadius) biotype ‘B’ on tomatoes under greenhouse conditions: (i) vertically placing yellow sticky cards either parallel or perpendicular to tomato rows at a rate of 1 per 3‐m row; (ii) releasing Eretmocerus sp. nr. rajasthanicus once at 30 adults/m² in the high whitefly density greenhouses (> 10 adults/plant), or twice at 15 adults/m² at a 5‐day interval in the low whitefly density greenhouses (< 10 adults/plant); and (iii) using combinations of yellow sticky cards that were placed vertically parallel to tomato rows and parasitoids released once at 30/m² in high whitefly density greenhouses or twice at 15/m² at a 5‐day interval in low whitefly density greenhouses. Our data show that yellow sticky cards trapped B. tabaci adults and significantly reduced whitefly populations on tomato. The yellow sticky cards that were placed parallel to tomato rows caught significantly more whitefly adults than those placed perpendicular to tomato rows on every sampling date. In the treatment where parasitoids were released once at 30/m² in high whitefly density greenhouses, the number of live whitefly nymphs were reduced from 4.6/leaf to 2.9/leaf in 40 days as compared with those on untreated plants on which live whitefly nymphs increased from 4.4/leaf to 8.9/leaf. In the treatment where parasitoids were released twice at 15/m² in low whitefly density greenhouses, the numbers of live nymphs of B. tabaci on tomato leaves were reduced from 2.1/leaf to 1.7/leaf in 20 days as compared with those on untreated plants on which numbers of live nymphs of B. tabaci increased from 2.2/leaf to 4.5/leaf. In the treatment of yellow sticky cards and parasitoid release once at 30/m² in high whitefly density greenhouses, the numbers of live nymphs of B. tabaci on tomato leaves were reduced from 7.2/leaf to 1.9/leaf, and in the treatment of yellow sticky cards and parasitoid release twice at 15/m² at a 5‐day interval at low whitefly density, the numbers of live nymphs of B. tabaci on tomato leaves were reduced from 2.5/leaf to 0.8/leaf; whereas the numbers of live nymphs of B. tabaci on untreated plants increased from 4.4/leaf to 8.9/leaf. An integrated program for management of B. tabaci on greenhouse vegetables by using yellow sticky cards, parasitoids and biorational insecticides is discussed.     

Genetic variation in Sanguisorba minor after 6 years in situ selection under elevated CO2

Genetic variation within plant species in their response to elevated CO₂ could be important for long‐term changes in plant community composition because it allows for selection of responsive genotypes. Six years of in situ CO₂ enrichment in a temperate grassland offered a unique opportunity to investigate such microevolutionary changes in a common herb of that plant community, Sanguisorba minor. Plants were grown from seeds collected at the end of a 6‐year treatment in either ambient or elevated CO₂. The resulting seedlings were grown under ambient or elevated CO₂ and with or without interspecific competition by Bromus erectus in the greenhouse for two seasons. The effect of competition was included because we expected selection under elevated CO₂ to favour increased competitive ability. Elevated CO₂ in the greenhouse and competition both caused a significant reduction of the total dry mass in S. minor, by 12% and 40%, respectively, with no interaction between CO₂ and competition. Genetic variation in all traits was substantial. Seed families responded differently to competition, but the family × greenhouse CO₂ interaction was rather weak. There was no main effect of the field CO₂ treatment on any parameter analysed in the greenhouse. However, the field CO₂ treatment did significantly interact with the greenhouse CO₂ treatment for the cumulative number of leaves, suggesting microevolutionary change in this plant trait. Families from ambient field CO₂ produced fewer leaves under elevated greenhouse CO₂, whereas families from elevated field CO₂ retained constant number of leaves in either greenhouse CO₂ treatment. Since this resulted in increased litter production of the families from elevated field CO₂ under elevated greenhouse CO₂, the microevolutionary response should, in turn, affect ecosystem functions through dry matter recycling.     

Allocation responses to CO2 enrichment and defoliation by a native annual plant Heterotheca subaxillaris

Among plants grown under enriched atmospheric CO₂, root:shoot balance (RSB) theory predicts a proportionately greater allocation of assimilate to roots than among ambient‐grown plants. Conversely, defoliation, which decreases the plant's capacity to assimilate carbon, is predicted to increase allocation to shoot. We tested these RSB predictions, and whether responses to CO₂ enrichment were modified by defoliation, using Heterotheca subaxillaris, an annual plant native to south‐eastern USA. Plants were grown under near‐ambient (400 μmol mol^?1) and enriched (700 μmol mol^?1) levels of atmospheric CO₂. Defoliation consisted of the weekly removal of 25% of each new fully expanded, but not previously defoliated, leaf from either rosette or bolted plants. In addition to dry mass measurements of leaves, stems, and roots, Kjeldahl N, protein, starch and soluble sugars were analysed in these plant components to test the hypothesis that changes in C:N uptake ratio drive shifts in root:shoot ratio. Young, rapidly growing CO₂‐enriched plants conformed to the predictions of RSB, with higher root:shoot ratio than ambient‐grown plants (P < 0.02), whereas older, slower growing plants did not show a CO₂ effect on root:shoot ratio. Defoliation resulted in smaller plants, among which both root and shoot biomass were reduced, irrespective of CO₂ treatment (P < 0.03). However, H. subaxillaris plants were able to compensate for leaf area removal through flexible shoot allocation to more leaves vs. stem (P < 0.01). Increased carbon availability through CO₂ enrichment did not enhance the response to defoliation, apparently because of complete growth compensation for defoliation, even under ambient conditions. CO₂‐enriched plants had higher rates of photosynthesis (P < 0.0001), but this did not translate into increased final biomass accumulation. On the other hand, earlier and more abundant yield of flower biomass was an important consequence of growth under CO₂ enrichment.     

Effect of shading and high temperature amplitude in greenhouse on growth,photosynthesis, yield and phenolic contents of tomato (Lycopersicum esculentum Mill.)

Low temperature is the major environmental factor that limits the optimal field production of tomato in the high altitude mountain regions. Studies were conducted to determine the feasibility of growing tomato, a temperature sensitive crop, in a naturally ventilated passive solar greenhouse with high temperature amplitude (24.7 ± 3.0 °C). The study also aimed to determine the application of shade net combined with low-cost greenhouse technology. Despite the temperature fluctuation from 6.6 ± 2.1 °C at night to 39.1 ± 4.7 °C day temperature, flowering and fruiting were observed under the greenhouse conditions. The marketable yield inside the greenhouse was 1.8-times higher compared to open-field. Shading significantly affected the photosynthesis and results in increased sub-stomatal CO₂ concentration. Shading resulted in delayed flowering and 48% reduction in marketable yield. Total phenolic contents (TPC) of tomato grown under open-field and greenhouse conditions were similar. However, greenhouse conditions resulted in a 35% decrease in total flavonoid contents (TFC) of tomato fruit. Shading reduced the TPC and TFC by 29 and 16%, respectively under greenhouse conditions.Supplementary InformationThe online version contains supplementary material available at 10.1007/s12298-021-01032-z.     

Photosynthetic responses of apricot (<Emphasis Type="Italic">Prunus armeniaca</Emphasis> L.) to photosynthetic photon flux density,leaf temperature,and CO<Subscript>2</Subscript> concentration

Two cultivars (Katy and Erhuacao) of apricot (Prunus armeniaca L.) were evaluated under open-field and solar-heated greenhouse conditions in northwest China, to determine the effect of photosynthetic photon flux density (PPFD), leaf temperature, and CO₂ concentration on the net photosynthetic rate (P _N). In greenhouse, Katy registered 28.3 μmol m⁻² s⁻¹ for compensation irradiance and 823 μmol m⁻² s⁻¹ for saturation irradiance, which were 73 and 117 % of those required by Erhuacao, respectively. The optimum temperatures for cvs. Katy and Erhuacao were 25 and 35 °C in open-field and 22 and 30 °C in greenhouse, respectively. At optimal temperatures, P _N of the field-grown Katy was 16.5 μmol m⁻² s⁻¹, 21 % less than for a greenhouse-grown apricot. Both cultivars responded positively to CO₂ concentrations below the CO₂ saturation concentration, whereas Katy exhibited greater P _N (18 %) and higher carboxylation efficiency (91 %) than Erhuacao at optimal CO₂ concentration. Both cultivars exhibited greater photosynthesis in solar-heated greenhouses than in open-field, but Katy performed better than Erhuacao under greenhouse conditions.