Net Assimilation Research Articles

Effect of micronutrients on growth and bulb production of LA hybrid lilium (Lilium longiflorum) cv. pavia

The experiment was conducted during the 2021–22 at ICAR-Indian Agricultural Research Institute, New Delhi to determine the effect of micronutrients on the growth and bulb production of LA hybrid lilium cv. pavia. The experiment's findings showed that applying micronutrients topically in combination was more beneficial than doing so topically alone. In contrast, a combination of ZnSO4 + MnSO4 @6 g/litre each sprayed at 40 and 60 days after planting performed better in terms of growth attributes, such as net assimilation rate (4.07 g/m2 leaf area/day), relative growth rate (9.46 mg/g/day), and specific leaf area (46.68 m2/kg). Bulb attributes included number of bulblets/plant (4.60), bulb circumference (14.97 cm), bulblets circumference (3.77 cm), weight of bulb (30.44 g), and bulblets (2.64 g) in LA hybrid lilium cv. pavia, whereas the control group showed the lowest interaction effect levels. This demonstrates that the growth of bulbous ornamental crops such as lilium benefits more from the combined administration of micronutrients. It results from the application of the ideal concentration of micronutrients at regular intervals, which increases photosynthetic rate. These micronutrients help plants accumulate biosynthates through a variety of activities and control metabolic processes that occur in plants. Additionally, they activate enzymes that enhance development and better distribute carbohydrates to various regions of the plant, such as carbonic dehydrogenase, peroxidase, tryptophan synthase, and catalase. Micronutrients are essential for all cellular and metabolic processes, and their optimal utilization enhances the quality of the crop.

Hyperaccumulation of metal in the apoplast contributes to the tolerance of the phytoremediator Pistia stratiotes L. to manganese-contaminated water

Phytoremediation of manganese (Mn)-contaminated water requires the selection of Mn-tolerant species. This study reports on physiological changes and Mn bioaccumulation in the aquatic macrophyte Pistia stratiotes cultivated under various MnCl2 concentrations: control, 80, 340, 600, 1000, 2000, and 4000 µM. Few visual symptoms of Mn toxicity, such as chlorosis, were observed after 10 days, especially in plants treated with 2000 and 4000 µM MnCl2. High Mn accumulation was recorded, with maximum values of 23,700 and 24,600 µg g−1 DW in the shoots and roots, respectively, at 4000 µM Mn, contrasting with 825.01 and 1587.53 µg g−1 DW in control plants. Cellular fractioning showed that Mn in shoots and roots was mainly associated with the cell wall, with approximately 90% of the Mn in roots detected in the apoplast. There were no significant changes in net CO2 assimilation or respiratory rates after 5 and 10 days of Mn exposure. These results demonstrate that P. stratiotes is a Mn hyperaccumulator species with excellent phytoremediation potential, as shown by its high bioaccumulation capacity and its ability to maintain photosynthetic efficiency under Mn stress.

Rubisco activity and activation state dictate photorespiratory plasticity in Betula papyrifera acclimated to future climate conditions

Plant metabolism faces a challenge of investing enough enzymatic capacity to a pathway without overinvestment. As it takes energy and resources to build, operate, and maintain enzymes, there are benefits and drawbacks to accurately matching capacity to the pathway influx. The relationship between functional capacity and physiological load could be explained through symmorphosis, which would quantitatively match enzymatic capacity to pathway influx. Alternatively, plants could maintain excess enzymatic capacity to manage unpredictable pathway influx. In this study, we use photorespiration as a case study to investigate these two hypotheses in Betula papyrifera. This involves altering photorespiratory influx by manipulating the growth environment, via changes in CO2 concentration and temperature, to determine how photorespiratory capacity acclimates to environmental treatments. Surprisingly, the results from these measurements indicate that there is no plasticity in photorespiratory capacity in B. papyrifera, and that a fixed capacity is maintained under each growth condition. The fixed capacity is likely due to the existence of reserve capacity in the pathway that manages unpredictable photorespiratory influx in dynamic environments. Additionally, we found that B. papyrifera had a constant net carbon assimilation under each growth condition due to an adjustment of functional rubisco activity driven by changes in activation state. These results provide insight into the acclimation ability and limitations of B. papyrifera to future climate scenarios currently predicted in the next century.

Chloroplast ATP synthase restricts photosynthesis under fluctuating light in tomato but not in maize

Photosynthesis in fluctuating light requires coordinated adjustments of diffusion conductance and biochemical capacity, but the role of chloroplast ATP synthase activity (gH+) in dynamic photosynthesis is not well understood. In this study, we measured gas exchange, chlorophyll fluorescence and electrochromic shift signals in fluctuating light for leaves of tomato (Solanum lycopersicum) and maize (Zea mays). During the transition from sun to shade, simultaneous increases in gH+, effective quantum yield of PSII, and net CO2 assimilation rate (AN) occurred in tomato but uncoupled in maize, indicating that gH+ limited AN during the sun-to-shade transition in tomato but not in maize. During the shade-to-sun transition, gH+ increased simultaneously with stomatal conductance, mesophyll conductance and Rubisco carboxylation capacity in tomato, suggesting that gH+ is an overlooked factor affecting light induction of AN in tomato. By comparison, gH+ maintained at high levels in maize and its AN was mainly restricted by stomatal conductance. Our results reveal that the kinetics of gH+ in fluctuating light differs between species, and chloroplast ATP synthase may be a potential target for improving dynamic photosynthesis in crops such as tomato.

Synergistic enhancement of biomass allocation from leaves to stem by far-red light and warm temperature can lead to growth reductions

The application of far-red (FR; 700–800 nm) light can improve plant growth, especially in leafy green vegetables, through enhancing leaf expansion and photon capture. However, higher levels of FR light may induce excessive stem elongation at the expense of leaf expansion. The morphological responses to FR light are mediated by phytochrome photoreceptors, with their activity further dependent on temperature. We aimed to quantify if different plant species respond differently to FR light and temperature conditions. Six economically-important plant species, including three cool-season species (lettuce, kale, and petunia) and three warm-season species (tomato, African marigold, and zinnia) were grown under three FR fractions [FR/(Red+FR); 0, 0.13, and 0.25] and two temperature set points (22 and 28 ℃) to characterize their growth and morphological responses. Increasing the FR fraction from 0 to 0.25 led to a 26–47 % increase in leaf expansion in lettuce, kale, petunia, and zinnia at 22 ℃. However, the total leaf area of tomato and African marigold decreased by 14–26 % as the FR fraction increased to 0.25 at 22 ℃. At a warmer temperature of 28 ℃, unlike the response observed under cooler temperature, increasing the FR fraction resulted in excessive stem elongation (a 36–101 % increase) and a 16–49 % reduction in leaf expansion in lettuce, kale, and petunia. For tomato, African marigold, and zinnia, the total leaf area increased by 15–26 % as the FR fraction increased from 0 to 0.13 at 28 ℃; however, further increasing the FR fraction from 0.13 to 0.25 resulted in a reduction in total leaf area. Across all six species, a high FR fraction combined with warm temperature synergistically stimulated stem elongation at the expense of leaf expansion. Shoot biomass responded to FR light and warm temperature similarly to leaf expansion in all six species. We further characterized the physiological responses to FR light and temperature in lettuce and tomato. In both crops, FR light generally increased the quantum yield of photosystem II, while decreasing the net CO2 assimilation rate per unit leaf area, chlorophyll and carotenoid contents, and chlorophyll a:b ratio. Additionally, FR light increased soluble sugar:starch ratio in leaves at 28 ℃, but not at 22 ℃, suggesting that the synergistic effect of FR light and warm temperature on stem elongation may be mediated by increased soluble sugar translocation from leaves to stem. We concluded that the enhanced stem growth under FR light and warm temperature can lead to reduced plant biomass. Our results further indicate that the interactive effects between FR light and temperature on plant growth and morphology were species-dependent, with distinct responses observed among species with different temperature preferences.

Up-regulation of nitrogen metabolism and chlorophyll biosynthesis by hydrogen sulfide improved photosystem photochemistry and gas exchange in chromium-contaminated bean (Phaseolus vulgaris L.) plants

Hydrogen sulfide (H₂S) is considered as plant growth promoter under heavy metal stress, though its specific effects on photosynthesis are rarely explored. This study investigates the protective effects of exogenous H2S donor sodium hydrosulfide (NaHS) on chlorophyll metabolism and photosystem II (PSII) function in 24-day-old bean plants exposed to 10 μM chromium (Cr) stress. Sodium hydrosulfide (100 μM) reduced Cr accumulation in both roots and leaves, leading to restored plant growth. Concomitantly, H₂S mitigated Cr-induced oxidative damages by decreasing reactive oxygen species levels and further enhancing antioxidant scavenging activities. This resulted in significant reductions in Cr-elevated leaf pheophytin and chlorophyllide levels by 59% and 67%, respectively. Furthermore, NaHS application increased levels of porphyrin and its precursor, 5-aminolevulinic acid (5-ALA), in Cr-stressed bean. The up-regulation in chlorophyll biosynthesis was associated with enhanced activities of glutamine synthetase and glutamate synthase, essential for glutamate (precursor of 5-ALA) production, as well as nitrate and nitrite reductase, leading to increased nitric oxide generation. Under Cr stress, H₂S significantly improved the electron transport rate, effective quantum yield of PSII, and photochemical quenching by 112%, 53%, and 38%, respectively, while reducing non-photochemical quenching by 50%. Furthermore, H₂S promoted net CO₂ assimilation and photosynthesis at saturating light, respectively, while reducing stomatal conductance and transpiration to maintain water balance. Exogenous H₂S restored respiration, as indicated by increased light saturation and compensation points in Cr-treated plants. Overall, these findings indicate that H₂S regulates photosynthesis in Cr-stressed bean by modulating nitrogen and chlorophyll metabolism, thereby optimizing PSII efficiency and gas exchange.

Model for estimating red mulberry leaf area using a genetic algorithm

The success of sericulture depends directly on the quality and quantity of mulberry leaves, as it is essential for the feeding and development of silkworm caterpillars and, consequently, influences the quality of the silk thread manufactured. The estimation of mulberry leaf area is important to have plant development and growth indicators, such as transpiration intensity, net assimilation rate, leaf area ratio, specific leaf area and leaf area index, which allow predicting crop productivity. Thus, the objective of this study was to develop and test a model capable of estimating the red mulberry leaf area using a genetic algorithm. The model was adjusted with the proposed stochastic optimization method. The mean error found for the tested dataset was approximately 228.17 mm2 in sample space with mean leaf area of 6515.55 mm2. The information generated allows applying the model to estimate red mulberry leaf area in future studies.

Biological Acclimatization of Micropropagated Al-Taif Rose (Rosa damascena f. trigintipetala (Diek) R. Keller) Plants Using Arbuscular Mycorrhizal Fungi Rhizophagus fasciculatus

Tissue culture is used to multiply Al-Taif rose (Rosa damascena f. trigintipetala (Diek) R. Keller) plants in order to meet the demands of the fragrance, cosmetic, and floriculture industries. The use of arbuscular mycorrhizal fungus (AMF) could potentially improve plant growth and acclimatization performance to ex vitro conditions. Thus, in the current study, we investigated how AMF Rhizophagus fasciculatus influences the growth, establishment, and physiological performance of micropropagated Al-Taif rose plants during the acclimatization stage. The growth and physiological parameters of the AMF-treated plants were evaluated after a 12 week growth period in the growth chambers. The plants treated with AMF exhibited greater height (25.53 cm) and biomass growth values for both shoot fresh weight (0.93 g/plant) and dry weight (0.030 g/plant), more leaves (11.3/plant), more leaf area (66.15 cm2), longer main roots (15.05 cm/plant), total root length (172.16 cm/plant), total root area (64.36 cm2/plant), and biomass from both fresh weight (383 mg/plant) and dry weight (80.00 mg/plant) of the plants. The plants treated with AMF also exhibited increased rates of net CO2 assimilation, stomatal conductance, and transpiration compared to the control plants. The proline content in the leaves and roots was significantly lower in the AMF-treated plants than untreated plants. The Fv/Fm ratio, which serves as an indicator of the intrinsic or maximal efficacy of Photosystem II (PSII) demonstrated a notable decline in the untreated Al-Taif rose plants. These results elucidate the advantageous impact of AMF colonization on micropropagated Al-Taif rose plants, thereby enhancing their resilience against adverse ex vitro conditions.

Short-term reoxygenation is not enough for the recovery of soybean plants exposed to saline waterlogging

The ability of plants to recover after stressful events is crucial for resuming growth and development and is a key trait when studying stress tolerance. However, there is a lack of information on the physiological responses and the time required to restore homeostasis after the stress experience. This study aimed to (i) enhance understanding of soybean photosynthesis performance during saline waterlogging and (ii) investigate the effects of this combined stress during the reoxygenation and recovery period. Soybean plants (cultivar PELBR10-6049 RR) were subjected to waterlogging, NaCl, or hypoxia + NaCl for 3 and 6 days. Afterward, plants were drained and allowed to recover for an additional two (short-term) and seven days (long-term). Compared to plants exposed to single stress, the combined hypoxia + NaCl treatment resulted in a lower net CO2 assimilation rate, ФPSII, and levels of photosynthetic pigments during the waterlogging period. Furthermore, hypoxia + NaCl increased foliar electrolyte leakage during waterlogging. In response to short-term reoxygenation, these negative effects were amplified, while prolonged reoxygenation resulted in a slight increase in biomass accumulation. In conclusion, full recovery was not achieved under any condition during the reoxygenation periods tested. Notably, the brief reoxygenation phase imposed greater stress than the initial stress conditions for plants facing combined stress. Although extended recovery increased biomass accumulation, it remained lower in plants previously subjected to saline waterlogging.

Trait component analysis of lettuce in response to daily light integrals at two growth stages

AbstractLittle is known about the relative impact of lighting duration and light intensity on lettuce production, as well as whether daily light integrals (DLIs) play a significant role during different plant growth stages. Four DLIs were tested: 8.64, 11.52, 12.96, and 17.28 mol m−2 day−1 as supplemental lighting, which were obtained from a combination of supplemental light intensities at 200 and 300 µmol m−2 day−1 for 12 and 16 h. Sunlight was used as control. A direct correlation was observed between DLIs and yield, total fresh weight, and total dry weight. Under supplemental lighting, relative growth rate (RGR) increased due to an increase in net assimilation rate (NAR) rather than in leaf area ratio (LAR). Plants in the seedling stage were more sensitive to an elevation in DLI than in the head stage. This was confirmed by a greater increase in NAR compared to their corresponding control under the same DLI. Increasing DLI also improved lettuce quality via reducing nitrate and increasing protein content. Higher DLIs (12.96 and 17.28 mol m−2 day−1) led to a decrease in maximum quantum yield of photosystem II and an increase in performance index. In conclusion, manipulating RGR through NAR adjustments proved to be more effective than changes in LAR, and adjusting supplemental DLI at each stage was necessary to achieve a larger NAR and, consequently, a larger RGR.

Integrated uses of organic and inorganic fertilisers to increase sesame productivity on coastal sand fields

Sesame is recognised as a valuable oil plant with potential health benefits due to its disease mitigating properties. It shows exceptional growth rates in light soil types, such as sandy beach soils which are often deemed infertile. To address the issue, it is necessary to apply eco-friendly fertilisers derived from animal manure. Consequently, research has focused on performance evaluation over two growing seasons, namely the dry and rainy seasons, on coastal sandy soils. Employing a split-plot design across three replicates, the study investigated the influence of planting time and cultivar on the growth and yield of sesame. The study aimed to assess the impact of mixed fertiliser application timing on sesame growth and yield, focusing on both quantitative and qualitative parameters across the rainy and dry seasons. Results indicated that applying a mixture comprising chicken manure and inorganic fertiliser at the planting time significantly affected several growth parameters. These included plant height, chlorophyll content, flowering time, number of branches, net assimilation rate, root volume, and total sesame oil content, particularly in the dry season. Specifically, employing a dosage of 24.75 g of inorganic NPK fertiliser, comprising 1.45 g of nitrogen, 0.74 g of phosphorus, and 1.25 g of potassium per plant at planting time during the dry season, demonstrated the most favourable outcomes in terms of growth, yield components, and soil fertility. This approach also yielded a remarkable 54.51% oil content in the cultivar ‘Sbr-1’.

Influence of Cow Dung Extract Complemented with Nutrient Solution on the Growth Performance of Lettuce (Lactuca sativa L)

Limited studies have focused on plant growth performance using organic-based solutions complemented with mineral elements in a hydroponic system. Thus, this study aimed to investigate the growth performance of lettuce (Lactuca sativa L.) as influenced by cow dung extract combined with a hydroponic nutrient solution. Treatments considered as four different levels of aerated cow dung extracts (C), viz., C1 = 50 g l-1, C2 =100 g l-1, C3 =150 g l-1 and C4 =200 g l-1 and four strengths of standard nutrient solution (S), viz, S1 = 30% of standard nutrient solution, S2 = 40% of standard nutrient solution, S3 = 50% of standard nutrient solution and S4 = 60% of standard nutrient solution. The experiment was carried out using a deep flow technique in a semi-greenhouse. Various growth and physiological parameters were measured in this experiment. The obtained data were subjected to statistical analysis with 4 replicates by analysis of variance (ANOVA) using SPSS. In the case of growth parameters, the tallest plant (23.54 cm), maximum number of leaves per plant (17.01) broadest leaf (13.32 cm), and the highest fresh weight (112.05 g/plant) were recorded from C3 while the lowest in C1. For hydroponic nutrient solution, the tallest plant (23.13 cm), the maximum number of leaves per plant (16.66), the widest leaf breath (14.17 cm), and the highest fresh weight (116.0 g/plant) were recorded from S4 while the lowest in S1. On the other hand, physiological traits viz. leaf area, net assimilation ratio, and relative growth rate were statistically higher in C3 and lowest in C1. In the nutrient solution, all physiological parameters were highest in S4 and the lowest in S1. In the case of the interaction effect, the highest fresh weight and almost all the parameters were found best in C3S4 and the lowest in C1S1. Therefore, the analysis showed that in terms of growth promotion properties hydroponic nutrient solution along with cow dung extract had a substantial impact and C3S4 was the most preferable treatment combination. Based on these findings, in a hydroponic system, an inorganic nutrient solution combined with organic liquid fertilizer derived from cow dung extract (as an alternative nutrient source) requires further improvements to achieve optimal growth and yield.

Photosynthetic Traits of Quercus coccifera Green Fruits: A Comparison with Corresponding Leaves during Mediterranean Summer

Fruit photosynthesis occurs in an internal microenvironment seldom encountered by a leaf (hypoxic and extremely CO2-enriched) due to its metabolic and anatomical features. In this study, the anatomical and photosynthetic traits of fully exposed green fruits of Quercus coccifera L. were assessed during the period of fruit production (summer) and compared to their leaf counterparts. Our results indicate that leaf photosynthesis, transpiration and stomatal conductance drastically reduced during the summer drought, while they recovered significantly after the autumnal rainfalls. In acorns, gas exchange with the surrounding atmosphere is hindered by the complete absence of stomata; hence, credible CO2 uptake measurements could not be applied in the field. The linear electron transport rates (ETRs) in ambient air were similar in intact leaves and pericarps (i.e., when the physiological internal atmosphere of each tissue is maintained), while the leaf NPQ was significantly higher, indicating enhanced needs for harmless energy dissipation. The ETR measurements performed on leaf and pericarp discs at different CO2/O2 partial pressures in the supplied air mixture revealed that pericarps displayed significantly lower values at ambient gas levels, yet they increased by ~45% under high CO2/O2 ratios (i.e., at gas concentrations simulating the fruit’s interior). Concomitantly, NPQ declined gradually in both tissues as the CO2/O2 ratio increased, yet the decrease was more pronounced in pericarps. Furthermore, net CO2 assimilation rates for both leaf and pericarp segments were low in ambient air and increased almost equally at high CO2, while pericarps exhibited significantly higher respiration. It is suggested that during summer, when leaves suffer from photoinhibition, acorns could contribute to the overall carbon balance, through the re-assimilation of respiratory CO2, thereby reducing the reproductive cost.

Two Western Pacific Tabernaemontana Species Contrast in Biomass Allocation and Leaf Physiological Plasticity to Sun and Shade

The ability of plants to modify biomass allocation and leaf phenotypes to best utilize available resources has been heavily studied. No Tabernaemontana species have been included in this research agenda. Therefore, Tabernaemontana pandacaqui Poir. and Tabernaemontana rotensis (Kaneh.) B.C. Stone plants were subjected to 24% or 100% sunlight and various traits were determined to compare the relative level of plasticity. Midday net carbon dioxide assimilation was greater for T. rotensis in sun-grown plants, but greater for T. pandacaqui in shade-grown plants. Saturating light intensity and midday Fv/Fm were greater for T. rotensis in sun-grown plants, but did not differ between the species for shade-grown plants. Light compensation intensity was greater for T. rotensis than T. pandacaqui in both light treatments. Apparent quantum yield was greater for T. pandacaqui shade-grown plants but was similar for the two species in sun-grown plants. Greater relative root growth in full sun compared with shade was exhibited by T. rotensis but not by T. pandacaqui. These findings indicated that T. pandacaqui develops functional traits that improve performance in shade-grown plants, and T. rotensis develops facultative traits that enable performance in sun-grown plants. These insights into how T. pandacaqui and T. rotensis respond to sun and shade conditions add to the knowledge needed to inform the selection of niche conditions when using them in managed mixed forest plantings such as conservation and restoration sites.

Nutrition for commercial flower production of Longiflorum asiatica (LA) hybrid under northern plains

The study was conducted during the winter seasons, comprising the various combinations of inorganic fertilizers (N, P2O5, and K2O) and organic manure (FYM). Treatment T24 [(25 t FYM+160 kg N+120 kg P2O5+100 kg K2O)/ha] emerged as the statistically significant treatment, outperforming others in respect of tallest plant (122.43 cm), leaf count per plant (79.33), leaf length (7.90 cm), and early flower bud initiation (28.01 days), bud initiation to colour shown (47.11 days), and colour shown to flower opening (6.10 days). This treatment also tended to show the longest flower retention on plant (15.30 days), number of flower buds per plant (4.20), bud length (8.96 cm), stalk length (110.10 cm), stalk diameter (0.96 cm), flower diameter (22.98 cm), total chlorophyll content (6.50 mg/g), leaf nitrogen (4.70%), potassium (4.10%), and net assimilation ratio (NAR) (0.0065 mg/cm2/ day). Treatment T23 [(25 t FYM+120 kg N+90 kg P2O5+75 kg K2O)/ha] proved next best treatment. The lowest value was recorded in T25 (Control). Overall, treatment T24 proved to be the most effective treatment statistically for the commercial flower production of LA hybrid lilium for northern Indian plains.

Comparative analysis of lowland rice (Oryza sativa L. var. PSB Rc18) performance across different farming systems

Organic farming is gaining recognition as a viable alternative to conventional methods, promising soil health preservation and sustained crop productivity with economic benefits. This study evaluated the physiological, growth, and yield responses of the PSB Rc18 rice variety and appraised its economic feasibility under different production systems. The experiment was laid out in Randomized Complete Block Design (RCBD) with four replications and three treatments: T1-best bet organic production system, T2-farmers’ organic production system in Leyte, and T3-farmers’ conventional production system in Leyte. The crop growth rate (CGR) of PSB Rc18 remained consistent across the different systems. However, the Net Assimilation Rate (NAR) peaked significantly between 42-56 days after transplanting (DAT) in the T2. Additionally, the Leaf Area Index (LAI) in T1 was comparable to that of T3. Rice grown under T1 reached heading and maturation earlier than T3. Although T3 produced the highest fresh straw, most productive tillers, and heaviest total biomass, the grain yield was similar across all production systems. Economically, T2 outperformed with a superior benefit-cost ratio of $0.55 and $0.94 per USD invested, considering both regular and premium prices for organic palay. These findings highlight organic farming practices' economic and agronomic viability, suggesting that promoting organic farming can be a beneficial alternative to conventional methods in Leyte. This study underscores the potential for integrating organic practices to enhance sustainability and economic outcomes in rice production, making both T1 and T2 significant options for farmers in Eastern Visayas.

Physiological and biochemical attributes of the association host-parasite Tamarix aphylla-Plicosepalus acacia

Parasitic plants have been viewed as pests since they are able to damage agricultural crops and forest trees. They establish vasculature connections with the hosts and withdraw the required nutritive resources. This study aimed to explore the physiological and biochemical effects of the parasitic plant Plicosepalus acacia on the host Tamarix aphylla. It was conducted on young fully expanded leaves from the uninfected and infected trees and the parasitic plant ‘in situ’. The parasite had higher net photosynthetic assimilation rate (A), transpiration rate (E) and stomatal conductance (gs) compared to the host. Equally, it had two-fold greater water potential (Ψ) and osmotic potential (Ψs). It accumulated high amount of K, while it avoided accumulation of the most trace and ultratrace elements. Otherwise, parasitism seemed to increase A, WUE, water uptake and accumulation of the most major, trace and ultra-trace elements, however it reduced the accumulation of osmolytes at the infected plants. Based on UPLC-MS approach, P. acacia seemed to use a group of composites to interact with the host, including oleamide as a protector metabolite against host's defense system, carvone to establish vasculature connections with the host, cuminaldehyde to weaken growth and proliferation of the host, and caprolactam to weaken the distal part of the host. In contrast, the host T. aphylla could be used pipecolinic acid and nicotinamide to regulate systemic resistance and to defense against the parasite infection. Finally, despite the defense molecular interactions between the two partners, the parasitic plant exhibited several beneficial effects on the host.

Drought and heat stress interactions modify photorespiration and hydrogen peroxide content in Silver fir.

Photorespiration (PR) greatly reduces net carbon assimilation in trees (by c. 25%), but has received recent attention particular for its potential role in stress-signaling through the accumulation of hydrogen peroxide (H2O2), a stress signaling agent. Despite an increasing frequency of drought and heat events affecting forests worldwide, little is known about how concurrent abiotic stressors may interact to affect PR and subsequent H2O2 accumulation in trees. Here, we sought to identify how drought and a compounded one-day heat treatment individually and interactively affect PR (determined under variable O2) in Abies alba Mill. seedlings. Additionally, we quantified foliar H2O2 accumulation and enzymatic scavenging via peroxidase in relation to PR rates. We found drought stress to slightly increase PR (+5.2%) during mild-drought (12 days, Ψmd = -0.85 MPa), but ultimately to decrease PR (-13.6%) during severe-drought (26 days, Ψmd = -1.70 MPa) compared to the control, corresponding to increasing non-stomatal limitations of photosynthesis (i.e., decreased electron transport rate). The response of PR to heat stress was dependent on soil water availability as heat stress increased PR in control seedlings (+37.8%), but not in drought-stressed seedlings. Decreased PR during severe-drought corresponded to ~2x lower foliar H2O2 compared to the control. Despite increased PR under heat stress in control seedlings, foliar H2O2 decreased to near-zero likely due to enhanced scavenging as observed in ~2x greater peroxidase activity. Our results demonstrate that carbon loss to PR during drought stress can be highly dynamic, depending on the severity of soil dehydration. Additionally, increased PR under abiotic stress does not necessarily lead to accumulated H2O2, as tight regulation by scavenging enzymes instead minimize oxidative stress, reducing stress-signaling potential.

Fe toxicity tolerance is advantageous in rice growth recovery after Fe stress alleviation

AbstractBackgroundFe toxicity often inhibits rice growth on acid sulfate soils in tropical coastal lowlands. Previous studies in plant physiology and breeding have focused on high‐Fe stress, but not on growth recovery after stress alleviation.AimsThe objective of this study was to elucidate the morphophysiological characteristics in rice growth recovery from high‐Fe stress.MethodsWe evaluated the seedling growths of Taichung65 (T65) (Fe toxicity‐tolerant) and Ciherang (susceptible) in hydroponic culture, during the period of high‐Fe stress (250 mg Fe2+ L−1 for 12 or 18 days) and after stress alleviation.ResultsThe plant growth rate during recovery was negatively correlated with the leaf bronzing score (damage symptoms due to Fe toxicity) at the end of high‐Fe stress, which in turn was negatively correlated with the shoot Fe concentration. After 18‐day stress, T65 showed greater growth recovery than Ciherang, attributable to its higher net assimilation rate, higher transpiration rate (water uptake/green leaf area), and greater increase in total root length during recovery. In particular, T65 showed vigorous lateral root development in nodal roots that emerged during the stress period and vigorous growth of nodal roots that emerged during recovery.ConclusionsOur results suggest that tolerance to high‐Fe stress confers an advantage in growth recovery. It is likely that tolerance to Fe toxicity contributes not only to the maintenance of green leaf area at the end of stress but also to quick root growth recovery, leading to vigorous water uptake and high photoassimilation capacity after stress alleviation.

Bioinoculation Strategies for Enhanced Growth and Development of Economically Important Dalbergia latifolia Roxb

The present experiment was conducted to evaluate the plant growth properties of the native rhizospheric microflora of Dalbergia latifolia, an important medicinal, timber and biofuel plant. A systemic isolation, characterization and identification of rhizospheric soil, collected indigenously, initially produced 45 numbers of fungi and 3 numbers of bacteria. Both groups of organisms were characterized for their extracellular useful activity, especially phosphate solubilisation potential, and presented in terms of solubilisation index and solubilisation efficiency. Two fungi and two bacteria with good phosphate solubilization activity, along with NPK and organic manure, were selected and used in a pot culture experiment to promote the growth and development of Dalbergia latifolia under nursery conditions. Data recorded on 90 Days of plant growth exhibited the growth promotion of inoculated plants over control uninoculated experimental set. Results obtained on morphological and physiological growth parameters exhibited that the application of Aspergillus flavus followed by Burkholderia territorii + org. manure showed maximum shoot height and inoculation of Burkholderia anthina + Aspergillus sp. + NPK was significantly higher leaf area. Significantly longer root has been observed in Burkholderia territorii. However, a difference was observed in the number of leaves in Aspergillus flavus. + Org. manure and higher numbers of branches were observed in Aspergillus flavus only as compared to uninoculated control. Coinoculation of Aspergillus flavus + Penicillium simplicissimum showed better performance in fresh and dry shoot biomass as compared to other treatments. Burkholderia territorii + Org.manure produced higher fresh biomass of roots and coinoculation of bacteria Burkholderia territorii + Burkholderia anthina helped in enhancing root dry biomass. Dual inoculation of Aspergillus flavus + Penicillium simplicissimum gives better result in both fresh biomass of leaves and dry biomass of leaves. Application of Aspergillus flavus + Penicillium simplicissimum enhanced the total fresh biomass of the seedlings whereas supplementation of Burkholderia anthina + Penicillium simplicissimum enhanced the total dry biomass. Coinoculation of Aspergillus flavus + Penicillium simplicissimum showed higher RGR and coinoculation of Burkholderia anthina + Aspergillus flavus + NPK showed quite higher Leaf area ratio (LAR cm2gm-1). Co inoculation of Burkholderia territorii + Burkholderia anthina + Organic Manure showed highest root-shoot ratio and Coinoculation of Penicillium simplicissimum + Org. manure showed higher Net assimilation rate (NAR). However, Bacterial and fungal inoculants were also used as potent bioinoculants for the growth and establishment of crops of forest tree species.