Carbon Dioxide Concentrations and Light Levels on Growth and Mineral Nutrition of Juvenile Cacao Genotypes

Cacao (Theobroma cacao L.) was grown as an understory tree in agroforestry systems where it received inadequate to adequate levels of photosynthetic photon flux density (PPFD). As atmospheric carbon dioxide steadily increased, it was unclear what impact this would have on cacao growth and development at low PPFD. This research evaluated the effects of ambient and elevated levels carbon dioxide under inadequate to adequate levels of PPFD on growth, physiological and nutrient use efficiency traits of seven genetically contrasting juvenile cacao genotypes. Growth parameters (total and root dry weight, root length, stem height, leaf area, relative growth rate and net assimilation rates increased, and specific leaf area decreased significantly in response to increasing carbon dioxide and PPFD. Increasing carbon dioxide and PPFD levels significantly increased net photosynthesis and water-use efficiency traits but significantly reduced stomatal conductance and transpiration. With few exceptions, increasing carbon dioxide and PPFD reduced macro–micro nutrient concentrations but increased uptake, influx, transport and nutrient use efficiency in all cacao genotypes. Irrespective of levels of carbon dioxide and PPFD, intraspecific differences were observed for growth, physiology and nutrient use efficiency of cacao genotypes.

In the production of grafted transplants, healing and acclimatization are the most critical processes for survival. We investigated the influence of the photosynthetic photon flux (PPF) and the carbon dioxide (CO2) concentration during healing and acclimatization on the photosynthetic characteristics and growth of grafted pepper transplants to determine the optimum environmental conditions for healing and acclimatization in a healing chamber with artificial lighting source. Grafted pepper transplants were healed and acclimatized under two levels of CO2 (374 or 1,013 μmol·mol−1) and four levels of PPF (dark, 50, 98 or 147 μmol·m−2·s−1) for six days. The CO2 exchange rates of the grafted pepper transplants significantly increased with increasing PPF during healing and acclimatization. The CO2 exchange rates were higher under elevated CO2 concentrations than ambient CO2 concentration. The effect of CO2 enrichment was greater in low light intensity. The CO2 exchange rates at 50, 98 or 147 μmol·m−2·s−1 under elevated CO2 concentrations were 511, 261, and 172%, respectively, compared to the ambient CO2 concentrations. The increase of photosynthesis led to an improvement in growth. The SPAD value, dry weight and leaf area were greater under higher PPF and CO2 concentrations. PPF also influenced the anatomical structures of the leaves, and the palisade and spongy tissue cells of the leaves irradiated with higher PPF were aligned more densely, with more chloroplasts and small empty space. When compared to the tunnel in the greenhouse with natural light, healing and acclimatization under high CO2 (1,000 μmol·mol−1) and PPF (150 μmol·m−2·s−1) conditions in the healing chamber promoted the growth and graft union formation of grafted pepper transplants. The results suggested that high-quality grafted pepper seedlings could be achieved by healing and acclimatization in a healing chamber where optimal conditions such as high PPF and CO2 were maintained within the range evaluated in this experiment.

Atmospheric carbon dioxide and irradiance are important factors affecting growth and yield of plants. Due to the wide variation in irradiance in natural plant stands and the reportedly increasing carbon dioxide concentration in the global atmosphere, it is essential to study the interacting effects of these factors on the growth and production of crop plants. Growth analysis techniques were used to study the interaction of atmospheric CO2 concentration (350 and 675 µl/l) and photosynthetic photon flux density (PPFD) (600 and 1200 µEM−2 s−1)on four species (including both seed and root crops) grown in controlled environment chambers of the Duke University Phytotron. The plants were soybean (Glycine max L. Merr.), radish (Raphanus sativus L.), sugarbeet (Beta vulgaris L.), and corn (Zea mays L.). Total dry matter production increased in all species of plants and at all growth stages with both increased CO2 concentration and PPFD levels, and the maximum dry matter was produced at the highest combined levels of CO2 and PPFD. The dry weight increase varied between the different species and between plant parts within a species. High levels of CO2 and PPFD caused a greater increase in net assimilation rate in the plants during early growth stages than in later stages because the first two or three young, rapidly growing leaves were very efficient photosynthetic organs. A high CO2 or PPFD level resulted in decreasing leaf area ratios with increasing plant age for all the species due to a rapid increase in stem and root growth later in fruit production, and to a decreasing specific leaf area.Corn, having the C4 pathway of photosynthesis, showed less response to increased CO2 and PPFD than the three C3 species. Increasing the atmospheric CO2 concentration from 350 to 675 µl/liter at low and high PPFD levels produced dry matter increases of 72.7 and 76.4%, respectively, in soybean, and 18.9 and 18.6%, respectively, in corn at 50 days after planting. None of the species tested were light saturated at levels available in the standard fluorescent and incandescent lighting as is shown by the increased growth when higher PPFD levels were obtained with a combination of multivapor and sodium lamps.

In effort to improve resource-use efficiency of indoor specialty-crop production, this study examined potential interactive effects of a range of photosynthetic photon flux densities (PPFDs) and carbon dioxide (CO 2 ) concentrations on growth and quality attributes of densely seeded baby-stage red lettuce ( Lactuca sativa cv. Rouxai). Growth PPFDs tested included 200, 300, 400, and 500 µmol·m −2 ·s −1 . Growth CO 2 concentrations tested included 400, 800, 1200, and 1600 µmol·mol −1 . Growth parameters including shoot fresh mass, shoot dry mass, and leaf area were measured after a 17-day cropping cycle. Quality attributes such as red pigmentation and chlorophyll concentration were quantified nondestructively. Energy consumption for lighting (kWh) was measured over the entire cropping cycle for each experimental treatment, and energy-use efficiency (EUE) was calculated as a function of shoot fresh mass produced per kWh of electricity expended for lighting. Results indicated significant PPFD × CO 2 interaction effects for all measured productivity parameters except chlorophyll concentration. CO 2 was the less-limiting factor, with crop-productivity responses maximizing at 1200 µmol·mol −1 . PPFD was the more-limiting factor, with no evidence of light saturation at any PPFD/CO 2 combination tested. Although both PPFD and CO 2 influenced pigmentation, chlorophyll concentration was more strongly affected by PPFD. EUE was highest at the lowest PPFD tested across all CO 2 concentrations and declined with increasing PPFD. In addition to establishing a PPFD × CO 2 profile for baby-stage lettuce production, our findings suggest that from the industry standards of 800 µmol·mol −1 CO 2 and 200 µmol·m −2 ·s −1 PPFD, increasing PPFD further can lead to four to nine more cropping cycles per year, which possibly could offset increased electricity costs, particularly with premium market pricing for baby-stage lettuce. The choice of PPFD dictating CO 2 concentration to achieve production goals may be determined by incorporating the findings of this study into comprehensive cost-benefit analyses.

Chapter 1: Nutrient use efficiency in plants: an overview.- Part I: Nutrients as a Key Driver of Nutrient Use Efficiency.- Chapter 2: Soils and Inputs Management Options for Increasing Nutrient Use Efficiency.- Chapter 3: Nutrient and water use efficiency in soil: The influence of geological mineral amendments.- Chapter 4: Resource conserving techniques for improving nitrogen use-efficiency.- Chapter 5: Strategies for enhancing phosphorus efficiency in crop production systems.- Chapter 6: Efficiency of soil and fertilizer phosphorus use in time: a comparison between recovered struvite, FePO4-sludge, digestate, animal manure and synthetic fertilizer.- Chapter 7: Strategies for Enhancing Zinc Efficiency in Crop Plants.- Chapter 8: Nitrification inhibitors: classes and its use in nitrification management.- Part-II: Microbiological aspects of Nutrient Use Efficiency.- Chapter 9: Role of Microorganisms in Plant Nutrition and Health.- Chapter 10: Role of Cyanobacteria in Nutrient Cycle and Use Efficiency in the Soil.- Chapter 11: Trichoderma improves nutrient use efficiency in crop plants.- Chapter 12: Bio-priming mediated nutrient use efficiency of crop species.- Chapter 13: Unrealized potential of seed biopriming for versatile agriculture.- Part-III: Molecular and physiological aspects of Nutrient Use Efficiency.- Chapter 14: Improving nutrient use efficiency by exploiting genetic diversity of crops.- Chapter 15: Micro RNA based approach to improve nitrogen use efficiency in plants.- Chapter 16: Biofortification for selecting and developing crop cultivars denser in iron and zinc.- Chapter 17: Understanding genetic and molecular bases of Fe and Zn accumulation towards development of micronutrient enriched maize.- Part-IV: Nutrient Use Efficiency of Crop Species.- Chapter 18: Nitrogen uptake and use efficiency in rice.- Chapter 19: Nutrient-use efficiency in Sorghum.- Chapter 20: Improving nutrient use efficiency in oilseeds Brassica.- Chapter 21: Strategies for higher nutrient use efficiency and productivity in forage crops.- Chapter 22: Integrated nutrient management in potato for increasing nutrient use efficiency and sustainable productivity.- Part-V: Specialised Case Studies.- Chapter 23: Enhancing Nutrient Use Efficiencies in Rainfed Systems.- Chapter 24: Dynamics Of Plant Nutrients, Utilization And Uptake, And Soil Microbial Community In Crops Under Ambient And Elevated Carbon Dioxide.- Chapter 25: Phytometallophore Mediated Nutrient Acquisition by Plants.

The objective of this study was to determine the dry weight, height, and leaf area growth responses of impatiens (Impatiens walerana Hook. f.) plug seedlings to air temperatures ranging from 18 to 29C. The conditions maintained in the controlled-environment growth rooms (CEGR) were ambient C02 levels, 24-h lighting, and photosynthetic photon flux (PPF) ranging from ≈215; to 335 μmol·m-2·s-1. Mean daily temperatures of the plug medium ranged from 19.6 to 27.7C. At the higher PPF level, shoot dry weight decreased at plug medium temperatures (PMT) > 25C; at lower PPF levels (<300 μmol·m-2·s-1), shoot dry weight continued to increase with PMT > 25C. The mean relative growth rate (MRGR) of shoot dry weight was positively correlated with PMT during the initial growth period (up to 14 days from sowing) and was negatively correlated thereafter. The maximum MRGR was predicted to occur at 11.7 days from sowing for a PMT of 19.6C, at 10.8 days for a PMT of 21.6C, and at 9.7 days for a PMT of 23.6C. Linear regression coefficients of shoot height as a function of PMT were substantially higher for seedlings grown at lower PPF than those for seedlings from the highest PPF level. Seedling leaf area consistently increased with increasing temperature. Net assimilation rate (NAR) decreased with increasing seedling age NAR increased with increasing PPF. A decrease in NAR was apparent at 29C relative to values at the lower temperatures. Leaf area ratio (LAR) declined with increasing seedling age and PPF; a quadratic relationship of LAR as a function of PMT indicates a minimum LAR at 22.5C. The seedlings grown at 29C were excessively tall, had thin succulent leaves, and were judged unacceptable for shipping and transplanting. Maximum quality indices (i.e., dry weight per height) were found at PMT of 24.3 to 25.OC for 10- to 14-day-old seedlings and at PMT of 23.0 to 24.OC for 16- to 20-day-old seedlings.

A factorial analysis was conducted to investigate the effects of different levels of photosynthetic photon flux (PPF) and CO2 concentration on the interactions between the vesicular–arbuscular endomycorrhizal fungus Glomus intraradices and potato plantlets (Solanum tuberosum) cultured in an in vitro tripartite system. We observed that CO2 enrichment from 350 to 10000 ppm stimulated root colonization by the fungus, and that this stimulation was more pronounced under high PPF (300 μmol m−2 s−1) than low PPF (60 μmol m−2 s−1). Consistent with these observations, the effects of G. intraradices on dry matter production in potato plantlets were strongly dependent on the CO2 and PPF levels during cultivation. There was no significant effect of the mycorrhizal fungus on dry matter production at 350 ppm of CO2. However, under the high CO2 concentration, mycorrhiza had opposite effects on dry matter production depending on the PPF: a decrease (−21%) and a stimulation (+25%) of dry matter production after 2 wk of growth under low and high PPF, respectively, were observed in presence of G. intraradices relative to plantlets grown in its absence. Furthermore, in mycorrhizal plantlets grown under high levels of both PPF and CO2, the chlorophyll and carotenoid contents as well as the quantum yields of photosynthetic electron transport and the photochemical quenching qP of the chlorophyll‐a fluorescence measured near the PPF during growth were all higher than in non‐infected plantlets. Our results therefore indicate that mycorrhizal G. intraradices can alleviate the down regulation of photosynthesis related to sink limitation, and its effect on dry matter production is strongly dependent on the levels of CO2 and PPF during growth which determine the balance between the photosynthetic carbon uptake by the plantlets and the carbon cost by the fungus.

The ornamental plant Aristolochia manchuriensis is a liana with large heart-shaped leaves. It is difficult to propagate by cuttings and therefore a propagation method in vitro has been developed. The basic medium for multiplication was that of Murashige and Skoog (1962), supplemented with 6-benzylaminopurine, 0.4 mg l -1 . During multiplication the following photosynthetic photon flux (PPF) levels were tested; 20, 40, 60, and 80 pmol m -2 s -1 Effects of PPF levels on multiplication stabilized after three subcultures (84 d); the PPF level 20 pmol m -2 s -1* resulted in the lowest multiplication rate (MR) per month (3.0), and 80 pmol m -2 s -1 in the highest MR per month (4.2). PPF level during multiplication also affected the subsequent rooting. The maximum percentage of rooted shoots was attained after a PPF level of 80 μmol-m -2 s -1 during multiplication. A prolonged period on the last multiplication medium before rooting (6 weeks instead of 4 weeks) increased the multiplication rate significantly but affected subsequent rooting negatively, which dropped from 41 % to 12 %. Darkness during the first days (1 d or 7 d) on the rooting medium, improved the percentage of rooted shoots. It was also beneficial to split the base of the shoot prior to rooting.

Past studies of the effects of varying levels of photosynthetic photon flux density (PPFD) on the morphology and physiology of the epiphytic Crassulacean acid metabolism (CAM) plant Tillandsia usneoides L. (Bromeliaceae) have resulted in two important findings: (1) CAM, measured as integrated nocturnal CO2 uptake or as nocturnal increases in tissue acidity, saturates at relatively low PPFD, and (2) this plant does not acclimate to different PPFD levels, these findings require substantiation using photosynthetic responses immediately attributable to different PPFD levels, e.g., O2 evolution, as opposed to the delayed, nocturnal responses (CO2 uptake and acid accumulation). In the present study, instantaneous responses of O2 evolution to PPFD level were measured using plants grown eight weeks at three PPFD (20-45, 200-350, and 750-800 μmol m(-2)s(-1)) in a growth chamber, and using shoots taken from the exposed upper portions (maximum PPFD of 800 μmol m(-2)s(-1)) and shaded lower portions (maximum PPFD of 140 μmol m(-2)s(-1)) of plants grown ten years in a greenhouse. In addition, nocturnal increases in acidity were measured in the growth chamber plants. Regardless of the PPFD levels during growth, O2 evolution rates saturated around 500 μmol m(-2)s(-1). Furthermore, nocturnal increases in tissue acidity saturated at much lower PPFD. Thus, previous results were confirmed: photosynthesis saturated at low PPFD, and this epiphyte does not acclimate to different levels of PPFD.

Seven C3 crop and three C3 weed species were grown from seed at 360 and at 700 cm3 m–3 carbon dioxide concentrations in a controlled environment chamber to compare dry mass, relative growth rate (RGR), net assimilation rate (NAR), leaf area ratio (LAR) and photosynthetic acclimation at ambient and elevated carbon dioxide. The dry mass at the final harvest at elevated carbon dioxide relative to that at ambient carbon dioxide was highly correlated with the RGR at the lower carbon dioxide concentration. This relationship could be quite common, because it does not require that species differ in the response of RGR or photosynthesis to elevated carbon dioxide, and holds even when species differ moderately in these responses. RGR was also measured for a limited period at the end of the experiment to determine relationships with leaf gas exchange measured at this time. Relative increases in RGR at elevated carbon dioxide at this time were more highly correlated with the relative increase in NAR at elevated carbon dioxide than with the response of LAR. The amount of acclimation of photosynthesis was a good predictor of the relative increase in NAR at elevated carbon dioxide, and the long‐term increase in photosynthesis in the growth environment. No differences between crops and weeds or between cool and warm climate species were found in the responses of growth or photosynthetic acclimation to elevated carbon dioxide.

Corn, with C4 photosynthetic metabolism, often has no photosynthetic or yield response to elevated carbon dioxide concentrations. In C3 species, the yield stimulation at elevated carbon dioxide concentrations often decreases with nitrogen limitation. I tested whether such a nitrogen interaction occurred in corn, by growing sweet corn in field plots in open top chambers at ambient and elevated (ambient + 180 mmol·mol-1) carbon dioxide concentrations for four seasons, with six nitrogen application rates, ranging from half to twice the locally recommended rate. At the recommended rate of nitrogen application, no carbon dioxide effect on production occurred. However, both ear and leaf plus stem biomass were lower for the elevated carbon dioxide treatment than for the ambient treatment at less than the recommended rate of nitrogen application, and higher at the highest rates of nitrogen application. There were no significant responses of mid-day leaf gas exchange rates to nitrogen application rate for either carbon dioxide treatment, and elevated carbon dioxide did not significantly increase leaf carbon dioxide assimilation rates at any nitrogen level. Leaf area index during vegetative growth increased more with nitrogen application rate at elevated than at ambient carbon dioxide. It is concluded that elevated carbon dioxide increased the responsiveness of corn growth to nitrogen application by increasing the response of leaf area to nitrogen application rate, and that elevated carbon dioxide increased the amount of nitrogen required to achieve maximum yields.

Elevated [CO2] enhances light interception and carboxylation efficiency in plants. The combined effects of [CO2] and photosynthetic photon flux density (PPFD) on stomatal morphology, leaf anatomy, and photosynthetic capacity in tomato seedlings remain unclear. This study subjected tomato seedlings (Solanum lycopersicum Mill. cv. Jingpeng No.1) to two [CO2] (ambient [a[CO2], 400 µmol·mol−1] and enriched [e[CO2], 800 µmol·mol−1]) and three PPFD levels (L; low[Ll: 200 µmol·m−2·s−1], moderate[Lm: 300 µmol·m−2·s−1], and high[Lh: 400 µmol·m−2·s−1]) to assess their interactive impacts. Results showed that e[CO2] and increased PPFD synergistically improved relative growth rate and net assimilation rate while reducing specific leaf area and leaf area ratio. Notably, e[CO2] decreased stomatal aperture (−13.81%) and density (−27.76%), whereas elevated PPFD promoted stomatal morphological adjustments. Additionally, Leaf thickness increased by 72.98% under e[CO2], with Lm and Lh enhancing this by 10.79% and 41.50% compared to Ll. Furthermore, photosynthetic performance under e[CO2] was further evidenced by improved chlorophyll fluorescence parameters (excluding non-photochemical quenching). While both e[CO2] and increased PPFD Photosynthetic performance under e[CO2] was further evidenced by improved chlorophyll fluorescence parameters (excluding non-photochemical quenching). Moreover, e[CO2]-Lh treatment maximized total dry mass and seedling health index. Correlation analysis indicated that synergistic optimization of stomatal traits and leaf structure under a combination of e[CO2] and increased PPFD enhanced light harvesting and CO2 diffusion, thereby promoting carbon assimilation. These findings highlight e[CO2]-Lh as an optimal strategy for tomato seedling growth, providing empirical guidance for precision CO2 fertilization and light management in controlled cultivation.

Environmental conditions and incorporation of nutrients into the growing medium can affect the fertilizer needs of bedding plants. To evaluate the effects of photosynthetic photon flux (PPF) and starter fertilizer on the fertilizer requirements of subirrigated plants, we grew wax begonias (Begonia semperflorens-cultorum Hort.) under three PPF levels (averaging 4.4, 6.2, and 9.9 mol·m-2·d-1) and four fertilizer concentrations [electrical conductivity (EC) of 0.15, 0.33, 0.86, and 1.4 dS·m-1] in a normal (with starter fertilizer, EC = 2.1 dS·m-1) and heavily leached (with little starter fertilizer, EC = 0.9 dS·m-1) growing medium. Except for shoot dry mass, we did not find any significant interactions between PPF and fertilizer concentration on any of the growth parameters. There was an interactive effect of fertilizer concentration and starter fertilizer on all growth parameters (shoot dry mass, leaf area, plant height, and number of flowers). When the growing medium contained a starter fertilizer, fertilizer concentration had little effect on growth. When the growing medium was leached before transplanting, growth was best with a fertilizer EC of 0.86 or 1.4 dS·m-1. Water-use efficiency (WUE) was calculated from 24-hour carbon exchange and evapotranspiration measurements, and used to estimate the required [N] in the fertilizer solution to achieve a target tissue N concentration of 45 mg·g-1. Increasing PPF increased WUE and the required [N] (from 157 to 203 mg·L-1 at PPF levels of 4.4 and 9.9 mol·m-2·d-1, respectively). The PPF effect on the required [N] appeared to be too small to be of practical significance, since dry mass data did not confirm that plants grown at high light needed higher fertilizer concentrations. Thus, fertilizer concentrations need not be adjusted based on PPF.

Leaf lettuce (Lactuca sativa L. cv. Greenwave) was grown in combinatory environments of electric conductivity (EC) of nutrient solution and photosynthetic photon flux (PPF) to investigate their influence on fresh weight and leaf area in plantlet and fresh weight of leaf at harvest. The experiments were conducted under the combinations of three levels of EC, of 1.0, 2.0 dS m−1 and tap water and three levels of PPF of 50, 100 and 150 μmol m−2 s−1 to examine fresh weight and leaf area of plantlet. Although PPF had no influence on fresh weight grown in tap water, fresh weight significantly increased as PPF increased in nutrient solution of EC 1.0 and 2.0 dS m−1. Leaf area cultured in tap water decreased as PPF increased, however leaf area greatly increased as PPF increased in nutrient solution of EC 1.0 and 2.0 dS m−1. Plantlet grown under two levels of nutrient solution as tap water and EC 1.0 dS m−1 and three levels of PPF 50, 100 and 150 μmol m−2 s−1 were transplanted to hydroponic system with EC 2.0 dS m−1, PPF 200 μmol m−2 s−1, photoperiod 14 h and temperature 24°C to investigate the effect of condition at germination and raising seedling stages on fresh weight at harvest. Fresh weight of leaf lettuce showed similar tendency as fresh weight of plantlet, and it was found that EC of nutrient solution and PPF at the stage of germination and raising seedling significantly influenced fresh weight at harvest.

Independent short-term effects of photosynthetic photon flux density (PPFD) of 50–400 µmol m−2 s−1, external CO2 concentration (C a) of 85–850 cm3 m−3, and vapor pressure deficit (VPD) of 0.9–2.2 kPa on net photosynthetic rate (P N), stomatal conductance (g s), leaf internal CO2 concentration (C i), and transpiration rates (E) were investigated in three cacao genotypes. In all these genotypes, increasing PPFD from 50 to 400 µmol m−2 s−1 increased P N by about 50 %, but further increases in PPFD up to 1 500 µmol m−2 s−1 had no effect on P N. Increasing C a significantly increased P N and C i while g s and E decreased more strongly than in most trees that have been studied. In all genotypes, increasing VPD reduced P N, but the slight decrease in g s and the slight increase in C i with increasing VPD were non-significant. Increasing VPD significantly increased E and this may have caused the reduction in P N. The unusually small response of g s to VPD could limit the ability of cacao to grow where VPD is high. There were no significant differences in gas exchange characteristics (g s, C i, E) among the three cacao genotypes under any measurement conditions.