High Rates Of Photosynthesis Research Articles

Integrated Morphological, Physiological and Molecular Analysis of the Drought Response in Cultivated and Wild Prunus L. Subgenera Cerasus Species

Knowledge about the genetic potential of wild Prunus species is important for recognizing gene pools in germplasm and developing effective strategies for germplasm conservation and breeding. In this study, cultivated sweet cherry (Prunus avium L.) and relative wild Cereus subgenus genotypes belonging to P. microcarpa Boiss and P. incana (Pall.) Batsch. species were assayed in controlled drought conditions performing an integrated morphological, physiological, genomic and transcriptomic analysis of the stress response. These analyses were performed under well-watered and water-deficient conditions analysing morphology of leaves, gas exchange parameters and chlorophyll content differently affected by drought, especially under long-term water deficiency. From a genomic point of view, these genotypes were characterized using simple sequence repeat (SSR) markers. Finally, in the analysis of the transcriptional responses, drought tolerance candidate genes were analysed by quantitative PCR (qPCR). From a morphological point of view, P. microcarpa showed less leaf area, height and diameter in comparison to P. incana and mainly P. avium. The highest rate of photosynthesis in genotypes differently was observed in the control treatment and the lowest rate viewed during stress. The analysed genes showed different responses to drought in the genotypes, and more detailed analysis techniques to explain the molecular mechanisms of drought tolerance are needed in these genotypes. Our results provide a significant contribution to the understanding of how P. incana and P. microcarpa respond to drought stress, which may help to explain molecular and physiological mechanisms associated with the response to the drought of cherries. Additionally, these results show that wild cherries can be considered as a genetic source of drought resistance in breeding programs.

Microbiological Characteristics of Three Stratified Lakes in the Nizhny Novgorod Region

Abstract—Three karst lakes were investigated in the Nizhny Novgorod region: Staropustynskie lakes Svyato and Nekrasov Bay and Lake Svetloyar. The studied lakes belonged to the mesotrophic-eutrophic polyhumous type and were characterized by stable stratification with signs of meromixia. Their water columns were divided into aerobic and anaerobic zones, with the bottom water containing sulfide. Fe(II) compounds were also present in the Staropustynskie lakes. In the Lake Nekrasov Bay, the mixolimnion showed a high rate of oxygenic photosynthesis, up to 1.2 µg С L–1 day–1, as well as a maximum of anoxygenic photosynthesis in the chemocline (0.030–0.706 µg С L–1 day–1) at a depth of 1.5–2.5 m. The peak of dark CO2 assimilation (0.146 µg С L–1 day–1) occurred at a depth of 1.5 m in the oxycline zone. Anoxygenic phototrophic bacteria (APB) were found in the Lakes Zaliv Nekrasova and Svyato at the boundary of light penetration. Green sulfur bacteria with short cell prosthecate outgrowths, “Ancalochloris sp.,” predominated. Consortia “Chlorochromatium aggregatum” and filamentous chlorobacteria “Chloronema giganteum” were also found, their cell sheaths accumulated ferric iron salts. In the Staropustynskie lakes, various morphotypes of iron bacteria formed clusters in the microaerobic zone. In Lake Svetloyar the chemocline was located at a depth of 16 m, outside the photic zone, and the conditions were unfavorable for APB growth. In the studied lakes, heterotrophic aerobic bacteria played the main role in the aerobic oxidation of sulfur compounds in the chemocline zone.

Genotypic variation in water relations and gas exchange of urban trees in Detroit, Michigan, USA

Increasing tree species diversity has become a key underpinning for communities to improve resilience of urban and community forests. Increasingly, urban forestry researchers are examining physiological traits to aid in selecting trees for urban sites. Knowledge of physiological responses also has implications for understanding species’ resilience to increased stresses associated with climate change. Here, we compare growth, leaf SPAD chlorophyll index, water relations, and gas exchange of seven genotypes of shade trees planted in two locations in downtown Detroit, MI, USA. Genotypes included Redpointe® maple (Acer rubrum ‘Frank Jr.’), Flashfire® maple (Acer saccharum ‘JFS-Caddo2′), Pacific Sunset® maple (Acer truncatum x platanoides ‘Warrenred’), Emerald City® tulip tree (Liriodendron tulipifera ‘JFS-Oz’), Chanticleer® pear (Pyrus calleryana ‘Glen’s Form’), swamp white oak (Quercus bicolor), and Emerald Sunshine® elm (Ulmus propinqua ‘JFS-Bieberich’). Trees were planted in either Lafayette Plaisance Park (Park), a large urban greenspace, or on the median of St. Aubin Avenue (Median), a nearby major thoroughfare. Tree height growth and leaf SPAD index were higher for trees planted in the Park location than on the Median. However, genotypic variation was larger than the effects of location or the interaction of Genotype × Location for most traits. Across measurement dates, midday leaf water potential was lowest for Pyrus trees and highest for Ulmus and Liriodendron trees. Pyrus and Quercus trees had relatively high rates of net photosynthesis (A) and stomatal conductance (gs) while Liriodendron, Acer saccharum, and Ulmus trees had low rates of A and gs. Liriodendron trees closed their stomata rapidly as leaf water potential (Ψw) declined (isohydric response), while Pyrus and Quercus trees maintained gs across a range of leaf Ψw (anisohydric response). Liriodendron trees also had the highest relative growth rates, suggesting that drought stress avoidance through isohydry is a viable drought tolerance mechanism in urban trees.

Effect of Moisture Stress on Physiological and Yield Responses of Common Bean Varieties at Lath House Condition, Hawassa University, Southern Ethiopia

Common bean is one of the most traditional foods, with social and economic importance, and is suitable for food security due to its short growing cycle and adaptability to different cropping systems. However, various constraints like biotic and abiotic factors reported for the low productivity of the crop. Therefore, the study was designed to identify the common bean varieties’ response on physiological properties and yield performance under different irrigation intervals in Lath House condition at Hawassa University, Ethiopia, from June, 2020, to September, 2020. The experiment was laid out in a completely randomized design with a factorial combination of seven common bean varieties (Awash-1, Awash-2, Dursitu, Fedis, Gofta, Nasir, and Tinike) and three moisture levels, eight day irrigation interval, four day irrigation interval, and daily watering with three replication. There was a significant main and interaction effects among the measured parameters. From those significantly affected parameters, the highest stomata numbers (25) were recorded from the Dursitu variety with a daily irrigation interval. The longest stomata aperture was observed with Gofta (133.76 nm) and Fedis varieties (131.13 nm) to daily irrigation and four day irrigation intervals, respectively. A wider stomata aperture was found in the Awash-1(12.6 nm) variety on a daily irrigation interval, and maximum stomata conductance (193.67) was obtained in the Tinike variety treated with a four day irrigation interval. The maximum relative leaf moisture content (96%) was found on the Awash-1 variety at a four day irrigation interval. Maximum water use efficiency was obtained from the Awash-1 (3.95) variety, which is an insignificant variation with the Awash-2 (3.85) and Gofta varieties (3.85) at a four day irrigation interval. Among the varieties, the highest photosynthesis rate (10.43 μmol·m−2·s−1) and transpiration rate (5.42 mmol·m−2·s−1) were obtained in the Gofta variety treated by a four day irrigation interval. In the photosynthetic pigment analysis, the highest leaf chl-a, chl-b, and chl-a + b concentration was recorded at 2.4 μg/ml, 1.53 g/ml, and 3.93 μg/ml, respectively, in the Gofta variety irrigated at a four days interval. The highest (0.586) chlorophyll fluorescence was obtained in the eight day irrigation interval. The highest proline content was found from the Awash-1 (0.78) variety regarding to drought stress condition. The highest pods plant−1 (9) and seed pod−1 (5) was found in the Awash-2 and Awash-1 varieties, respectively, at a four days irrigation interval and the highest main effect of 100 SW (39.48 g), (28.6 g) was found in the Fedis variety and at a four day irrigating interval, respectively. The maximum yield was obtained from the varieties Awash-1 (7.8 g plant−1) and Gofta (7.36 g plant−1) with a four day irrigated interval and they are also superior at drought condition and Awash-2 varieties are enhanced at waterlogging condition as compared to the other varieties.

Disomic Substitution of 3D Chromosome with Its Homoeologue 3E in Tetraploid Thinopyrum elongatum Enhances Wheat Seedlings Tolerance to Salt Stress

The halophytic wild relatives within Triticeae might provide valuable sources of salt tolerance for wheat breeding, and attempts to use these sources of tolerance have been made for improving salt tolerance in wheat by distant hybridization. A novel wheat substitution line of K17-1078-3 was developed using common wheat varieties of Chuannong16 (CN16), Zhengmai9023 (ZM9023), and partial amphidiploid Trititrigia8801 (8801) as parents, and identified as the 3E(3D) substitution line. The substitution line was compared with their parents for salt tolerance in hydroponic culture to assess their growth. The results showed that less Na+ accumulation and lower Na+/K+ ratio in both shoots and roots were achieved in K17-1078-3 under salinity compared to its wheat parents. The root growth and development of K17-1078-3 was less responsive to salinity. When exposed to high salt treatment, K17-1078-3 had a higher photosynthesis rate, more efficient water use efficiency, and greater antioxidant capacity and stronger osmotic adjustment ability than its wheat parents. In conclusion, a variety of physiological responses and root system adaptations were involved in enhancing salt tolerance in K17-1078-3, which indicated that chromosome 3E possessed the salt tolerance locus. It is possible to increase substantially the salt tolerance of wheat by the introduction of chromosome 3E into wheat genetic background.

Improved air quality leads to enhanced vegetation growth during the COVID–19 lockdown in India

The direct effect of pandemic induced lockdown (LD) on environment is widely explored, but its secondary impacts remain largely unexplored. Therefore, we assess the response of surface greenness and photosynthetic activity to the LD-induced improvement of air quality in India. Our analysis reveals a significant improvement in air quality marked by reduced levels of aerosols (AOD, −19.27%) and Particulate Matter (PM 2.5, −23%) during LD (2020)from pre-LD (March–September months for the period 2017–2019). The vegetation exhibits a positive response, reflected by the increase in surface greenness [Enhanced Vegetation Index (EVI, +10.4%)] and photosynthetic activity [Solar Induced Fluorescence (SiF, +11%)], during LD from pre-LD that coincides with two major agricultural seasons of India; Zaid (March–May) and Kharif (June–September). In addition, the croplands show a higher response [two-fold in EVI (14.45%) and four-fold in SiF (17.7%)] than that of forests. The prolonged growing period (phenology) and high rate of photosynthesis (intensification) led to the enhanced greening during LD owing to the reduced atmospheric pollution. This study, therefore, provides new insights into the response of vegetation to the improved air quality, which would give ideas to counter the challenges of food security in the context of climate pollution, and combat global warming by more greening.

Rice (Oryza sativa) alleviates photosynthesis and yield loss by limiting specific leaf weight under low light intensity.

The physiological mechanisms of shade tolerance and trait plasticity variations under shade remain poorly understood in rice (Oryza sativa L.). Twenty-five genotypes of rice were evaluated under open and shade conditions. Various parameters to identify variations in the plasticity of these traits in growth irradiance were measured. We found wide variations in specific leaf weight (SLW) and net assimilation rate measured at 400µmolm-2 s-1 photosynthetic photon flux density (PPFD; referred to as A 400 ) among the genotypes. Under shade, tolerant genotypes maintained a high rate of net photosynthesis by limiting specific leaf weight accompanied by increased intercellular CO2 concentration (C i ) compared with open-grown plants. On average, net photosynthesis was enhanced by 20% under shade, with a range of 2-30%. Increased accumulation of biomass under shade was observed, but it showed no correlation with photosynthetic plasticity. Chlorophyll a /b ratio also showed no association with photosynthetic rate and yield. Analysis of variance showed that 11%, 16%, and 37% of the total variance of A 400 , SLW, and C i were explained due to differences in growth irradiance. SLW and A 400 plasticity in growth irradiance was associated with yield loss alleviation with R 2 values of 0.37 and 0.16, respectively. Biomass accumulation was associated with yield loss alleviation under shade, but no correlation was observed between A 400 and leaf-N concentration. Thus, limiting specific leaf weight accompanied by increased C i rather than leaf nitrogen concentration might have allowed rice genotypes to maintain a high net photosynthesis rate per unit leaf area and high yield under shade.

Algal sensitivity to nickel toxicity in response to phosphorus starvation

In all living cells, phosphorus plays an important function in the transport of metabolic energy and as a structural component of nucleotide and phospholipid molecules. Ni2+ is found in industrial water effluent and has the potential to harm aquatic ecosystems. The study was designed to assess the effect of phosphorous-limiting conditions in combination with the absence or presence of different concentrations of nickel on growth, pigment content, photosynthesis, and respiration activities of the studied alga Dunaliella tertiolecta. The EC50 for dissolved nickel was around 15 mg/L. Results obtained showed that, growth and chlorophyll content under phosphorus limiting conditions increased under low concentrations of dissolved nickel. The amount of O2-evolution with phosphorus limiting conditions was lower than those of untreated normal cultures. Lower dissolved nickel concentrations resulted in higher photosynthesis rates in the treated phosphorus-starved cultures than higher concentrations. The degree of response to metal toxicity in phosphorus-starved medium is depending mainly on the concentration of the element and the length of the culturing period and it was less than those in normal control culture containing phosphorus.

Adaptive strategy of Stevia rebaudiana to environmental change in tropical climate based on anatomy and physiology characteristics

Abstract. Khuluq AD, Widaryanto E, Ariffin, Nihayati E. 2022. Adaptive strategy of Stevia rebaudiana to environmental change in tropical climate based on anatomy and physiology characteristics. Biodiversitas 23: 5710-5717. High solar radiation and air temperature are the main influencing factors for plant growth and development in tropical climates. This study's objective was to understand stevia adaptation to microclimate changes at several altitudes in tropical climates. The study was conducted in a completely randomized design with altitude differences consisting of highlands, medium lands, and lowlands with ten replicates. The results showed that stevia was exposed to temperatures above 20oC during growth in the highlands by 36.46%, and in the medium lands to lowlands by 92.85%-93.96%. Meanwhile, the temperature above 30oC in the lowlands is 17.98% highest of the others. Stevia adapts to a high temperatures by increasing stomatal density, trichomes, and photosynthesis rate. Moreover, decreasing stomata (width, aperture, open percentage), leaf thickness, palisade length, xylem diameter, conductance, and transpiration rate. Stevia in the medium lands shows good adaptability with a high photosynthesis rate, percentage of open stomata 93.15%, leaf thickness 382.56 µm, and xylem diameter 30.97 µm, which is no different from the highlands. Thus, the medium lands have the potential as a new area of stevia development in a tropical climate, considering the increasingly competitive use of agricultural land in the highlands.

Delaying drought-driven leaf cell damage may be the key trait of invasive trees ensuring their success in the Mediterranean basin.

Invasive alien species (IAS) threaten the biodiversity richness of the Mediterranean basin, a drought-prone region. However, our knowledge on the adaptive strategies of IAS for facing Mediterranean drought summers is still incomplete. The aim of the present study is to compare the water relations and the critical relative water content (RWC) values leading to loss of cell rehydration capacity of two Mediterranean basin IAS (i.e., Ailanthus altissima (Mill.) Swingle and Robinia pseudoacacia L.) versus two co-occurring native species (i.e., Fraxinus ornus L.and Quercus pubescensWilld.). Study IAS showed higher values of water potential at turgor loss point and osmotic potential at full turgor, lower values of modulus of elasticity and leaf mass area but higher photosynthesis rate, even during the summer, with respect to the Mediterranean native species. These findings supported the hypothesis that IAS are characterized by a resource acquisitive strategy coupled with a safety-efficiency trade-off, compared with Mediterranean native species. However, similar leaf RWC thresholds leading to loss of cell rehydration capacity were recorded in the two groups of species. Moreover, IAS showed higher saturated water content and capacitance values compared with the co-occurring species. Overall, our results suggest that the success of Mediterranean IAS is driven by their ability to delay dehydration damage of mesophyll cells during Mediterranean summer drought, thereby supporting their distinctive high carbon assimilation rate.

Does constant or changing light give the best rooting of hibiscus cuttings of two sizes?

In this experiment the effect of light intensity (photosynthetic photon flux density, PPFD) and cutting size (10 and 7 cm) was investigated during five weeks rooting of hibiscus (Hibiscus rosa-sinensis L. ‘Adonicus Yellow’). The light regimes included three constant PPFD: 16, 76 and 151 µmol m−2 s−1; and three changing PPFD after two weeks: 16 → 76, 16 → 151 and 76 → 151 µmol m−2 s−1. The light intensity has a dual effect, promoting photosynthesis and carbohydrate production, but also water loss through transpiration with the potential for desiccating the cutting. The treatments starting with 16 µmol m−2 s−1 insufficiently supported the rooting process, illustrated by the lack shoot growth after two weeks. Within each treatment type (constant or changing PPFD) the root formation was linearly correlated to the total light integral for the propagation period (r2 = 0.835–1.000) for respective cutting size. The changing PPFD treatments showed the strongest response to increasing light integral with the [76 → 151] treatment producing most roots for both cutting sizes, despite the constant 151 µmol m−2 s−1 having the highest total light integral. This indicates that conserving water is of crucial importance before root emergence in the third week of rooting. The 7 cm cuttings produced more root biomass and had higher root:shoot ratio than the 10 cm cuttings. The 7 cm cuttings had higher rates of photosynthesis one week after rooting, probably due to higher sink demand from the growing roots and mobilised more soluble sugars from the leaves. The rooting process takes five weeks and does not demand high light, so the results are promising for moving propagation of hibiscus from the greenhouse to a vertical production system based on light emitting diodes (LEDs) to save production area for final production.

Intraspecific Leaf Trait Variation across and within Five Common Wine Grape Varieties.

Variability in traits forming the Leaf Economics Spectrum (LES) among and within crop species plays a key role in governing agroecosystem processes. However, studies evaluating the extent, causes, and consequences of within-species variation in LES traits for some of the world’s most common crops remain limited. This study quantified variations in nine leaf traits measured across 90 vines of five common wine grape (Vitis vinifera L.) varieties at two growth stages (post-flowering and veraison). Grape traits in these varieties covary along an intraspecific LES, in patterns similar to those documented in wild plants. Across the five varieties evaluated here, high rates of photosynthesis (A) and leaf nitrogen (N) concentrations were coupled with low leaf mass per area (LMA), whereas the opposite suite of traits defined the “resource-conserving end” of this intraspecific LES in grape. Variety identity was the strongest predictor of leaf physiological (A) and morphological traits (i.e., leaf area and leaf mass), whereas leaf chemical traits and LMA were best explained by growth stage. All five varieties expressed greater resource-conserving trait syndromes (i.e., higher LMA, lower N, and lower Amass) later in the growing season. Traits related to leaf hydraulics, including instantaneous water-use efficiency (WUE), were unrelated to LES and other resource capture traits, and were better explained by spatial location. These results highlight the relative contributions of genetic, developmental, and phenotypic factors in structuring trait variation in the five wine grape varieties evaluated here, and point to a key role of domestication in governing trait relationships in the world’s crops.

СЕЗОННАЯ ИЗМЕНЧИВОСТЬ ПОТОКОВ ДИОКСИДА УГЛЕРОДА, ЯВНОГО И СКРЫТОГО ТЕПЛА В СЕВЕРОТАЕЖНОМ ЛИСТВЕННИЧНОМ ЛЕСУ СРЕДНЕЙ СИБИРИ ПО ДАННЫМ ПУЛЬСАЦИОННЫХ ИЗМЕРЕНИЙ

The seasonal and daily variability of sensible and latent heat and carbon dioxide (CO2) fluxes, as well as the sensitivity of the fluxes to changing environmental conditions were derived by the eddy covariance flux measurements in an undisturbed northern-taiga larch forest on continuous permafrost in Central Siberia from the end of May to the end of September in 2013 and 2015. The measurements showed a high seasonal and daily variability of CO2, sensible and latent heat fluxes. It was found that whereas dry and sunny weather conditions of June and July in 2013 and 2015 resulted in lower daily latent heat fluxes as compared to sensible ones, mostly cloudy and rainy weather in the second half of the summer led to the reduced net radiation and increased latent heat fluxes. The daily values of gross primary production from the beginning of June to mid-August in 2013 and 2015 exceeded the values of the ecosystem respiration, and the forest ecosystem was the sink of CO2 from the atmosphere. The maximum CO2 uptake was observed in late June and early July, primarily due to high photosynthesis rates influenced by high incoming solar radiation, optimal air temperature, and soil moisture conditions. Since mid-August, the balance between the CO2 uptake and release was close to zero. The total net ecosystem CO2 exchange during the growing season of 2013 was -76.5 g C/m2, while it was slightly higher (-103.6 g C/m2) during the growing season of 2015, primarily due to higher air temperatures in June and greater precipitation in the summer months of 2015.

The differential ability of two species of seagrass to use carbon dioxide and bicarbonate and their modelled response to rising concentrations of inorganic carbon.

Seagrass meadows are one of the most productive ecosystems on the planet, but their photosynthesis rate may be limited by carbon dioxide but mitigated by exploiting the high concentration of bicarbonate in the ocean using different active processes. Seagrasses are declining worldwide at an accelerating rate because of numerous anthropogenic pressures. However, rising ocean concentrations of dissolved inorganic carbon, caused by increases in atmospheric carbon dioxide, may benefit seagrass photosynthesis. Here we compare the ability of two seagrass from the Mediterranean Sea, Posidonia oceanica (L.) Delile and Zostera marina L., to use carbon dioxide and bicarbonate at light saturation, and model how increasing concentrations of inorganic carbon affect their photosynthesis rate. pH-drift measurements confirmed that both species were able to use bicarbonate in addition to carbon dioxide, but that Z. marina was more effective than P. oceanica. Kinetic experiments showed that, compared to Z. marina, P. oceanica had a seven-fold higher affinity for carbon dioxide and a 1.6-fold higher affinity for bicarbonate. However, the maximal rate of bicarbonate uptake in Z. marina was 2.1-fold higher than in P. oceanica. In equilibrium with 410 ppm carbon dioxide in the atmosphere, the modelled rates of photosynthesis by Z. marina were slightly higher than P. oceanica, less carbon limited and depended on bicarbonate to a greater extent. This greater reliance by Z. marina is consistent with its less depleted 13C content compared to P. oceanica. Modelled photosynthesis suggests that both species would depend on bicarbonate alone at an atmospheric carbon dioxide partial pressure of 280 ppm. P. oceanica was projected to benefit more than Z. marina with increasing atmospheric carbon dioxide partial pressures, and at the highest carbon dioxide scenario of 1135 ppm, would have higher rates of photosynthesis and be more saturated by inorganic carbon than Z. marina. In both species, the proportional reliance on bicarbonate declined markedly as carbon dioxide concentrations increased and in P. oceanica carbon dioxide would become the major source of inorganic carbon.

The leaf economics spectrum of triploid and tetraploid C4 grass Miscanthus x giganteus.

The leaf economics spectrum (LES) describes multivariate correlations in leaf structural, physiological and chemical traits, originally based on diverse C3 species grown under natural ecosystems. However, the specific contribution of C4 species to the global LES is studied less widely. C4 species have a CO2 concentrating mechanism which drives high rates of photosynthesis and improves resource use efficiency, thus potentially pushing them towards the edge of the LES. Here, we measured foliage morphology, structure, photosynthesis, and nutrient content for hundreds of genotypes of the C4 grass Miscanthus× giganteus grown in two common gardens over two seasons. We show substantial trait variations across M.× giganteus genotypes and robust genotypic trait relationships. Compared to the global LES, M.× giganteus genotypes had higher photosynthetic rates, lower stomatal conductance, and less nitrogen content, indicating greater water and photosynthetic nitrogen use efficiency in the C4 species. Additionally, tetraploid genotypes produced thicker leaves with greater leaf mass per area and lower leaf density than triploid genotypes. By expanding the LES relationships across C3 species to include C4 crops, these findings highlight that M.× giganteus occupies the boundary of the global LES and suggest the potential for ploidy to alter LES traits.

Effects of light intensity on the growth of Polygala fallax Hemsl. (Polygalaceae).

Polygala fallax Hemsl. (Polygalaceae), a traditional Chinese medicinal species, requires optimal growth conditions for artificial cultivation. Irradiance is one of the primary environmental factors that affects the growth and survival of P. fallax Hemsl. plants, which seemingly grow better under weak irradiance conditions. However, the optimum light intensity for growing P. fallax Hemsl. is not clear. To determine the optimum light intensity for cultivating this medicinal plant species, P. fallax Hemsl. plants from two different habitats were grown and exposed to three shade treatments (50% shade, 70% shade and 90% shade, which resulted in photosynthetically active radiation amounts equal to 662 μmol m−2 s−1, 401 μmol m−2 s−1, and 131 μmol m−2 s−1, respectively) to evaluate survival, growth, leaf photosynthesis, and the main pharmacological active ingredients (saponins) in response to shade. Our results revealed that the P. fallax Hemsl. plants in the different habitats consistently exhibited relatively high photosynthesis rates, biomass, survival rates and saponins under 662 μmol m−2 s−1 created by the 50% shade treatment. We concluded that photosynthetically active radiation of approximately 662 μmol m−2 s−1 is suitable for the cultivation of P. fallax Hemsl. plants.

Introgression of a novel gene AhBINR differentially expressed during PGPR Brachybacterium saurashtrense-Arachis hypogaea interaction enhances plant performance under nitrogen starvation and salt stress in tobacco

Plant growth-promoting rhizobacteria provide endurance during environmental stress conditions. Previously, we have shown that the interaction of the halotolerant diazotrophic bacteria Brachybacterium saurashtrense JG06 induces physio-biochemical and molecular changes in Arachis hypogaea under nitrogen starvation conditions. Here we deciphered the role of a novel gene AhBINR that was differentially overexpressed in A. hypogaea after interaction with B. saurashtrense JG06 under nitrogen deficit conditions. Overexpression of the AhBINR gene in the model plant (tobacco) showed higher growth parameters (root length, shoot length, fresh weight, and dry weight) under nitrogen starvation and salt stress in comparison to the wild type and vector control. Transgenic plants were enabled with a higher photosynthesis rate, which provides the support for better performance under N2 starvation and salt stress. Results showed that the transgenic plants overexpressing the AhBINR gene had better physiological status and lower ROS accumulation under adverse conditions. Microarray transcriptome analysis showed that the transcription factors, biotic and abiotic stress, photosynthesis, and metabolism-related genes were differentially expressed (total 736 and 6530 genes were expressed under nitrogen deficit and salt stress conditions, respectively at a 5-fold change level) in comparison to wild type plants. Overall results showed the involvement of the AhBINR gene in the activation of the abiotic stress (nitrogen starvation and salt stress) related pathways, which can be overexpressed after legume-rhizobacterial interaction.

COULD FULL SUN EXPOSURE REPRESENT PHYSIOLOGICAL ADVANTAGES FOR CRIOLLO COCOA CULTIVATION?

In Venezuela, the physiological performance of adult cocoa trees under full sun exposure is unknown. The long-term effect of high photon flux density (PFD) on leaf water potential (), leaf area index (LAI), gas exchange, photochemical activity of PSII, and photosynthetic pigment content in adult cocoa trees of Ocumare 61 (OC-61) was evaluated, in order to know if OC-61 could have a good photosynthetic performance in plants grown in full sun (E) or if on the contrary there is a physiological disadvantage compared to those grown in shade (S), self-shaded leaves were also evaluated in each condition (E+A and S+A). The OC-61 clone grown in E showed significant changes in some physiological traits: lower , lower IAF, higher rates of photosynthesis (A) and water use efficiency (WUE), lower intercellular CO2 concentration (Ci) and lower total chlorophyll, and carotenoid content. An increase in electron transport rate, PSII quantum efficiency, photochemical and non-photochemical extinction coefficient was found that would partially explain the higher A's in E; there was no decrease in maximum quantum efficiency indicating the absence of photoinhibition. Clone OC-61 is a shade tolerant crop; however, the results indicate that it can be acclimatized to high sun exposure without damage to PSII functioning, which could represent a physiological advantage for clone OC-61 grown in the study area.

Genetic differences as estimators of osmotic adjustment and source-sink balance in grapevine hybrid elites

This study deals with the best responses of a diverse collection of grapevine genotypes to osmotic stress associated with source-sink balance responses given by an estimator such as leaf area to fruit ratio. ‘Centennial Seedless’, a drought tolerant cultivar, was selected as control. The cultivars, ‘Victoria’ and ‘Argessis’, were chosen as a repetition from previous research dealing with pollen grain test, two years ago. Ten genotypes were hybrid elites in first and second hybrid generations. Three cultivars ‘Victoria’, ‘Centennial Seedless’, and ‘Argessis’ were grown under field conditions in containers, and in the soil under greenhouse conditions. Significant differences were found between genotypes for both responses to osmotic stress and source-sink balance. ‘Centennial Seedless’ and ‘BP9’ hybrid showed the best responses of induced osmotic adjustment; results confirmed the compensatory potassium uptake theory. ‘Victoria’ and ‘Argessis’ had almost the same average values as ‘Centennial Seedless’ osmotic estimator for induced osmotic adjustment. ‘Victoria’ and ‘HR7’ hybrid showed an increase in osmotic stress in the cell, after application of polyethylene glycol solutions without potassium cation and a lower source-sink ratio, which could be associated with higher photosynthesis rates. No correlations were identified between the mechanisms expressed by the analyzed estimators, indicating that they are activated and functional separately from each other, sometimes only compensatory.

Effects of Increased Temperature on Photosynthesis of C3 and C4 Plants

Photosynthesis is the process by which green plants synthesis their own food using sun light and carbon dioxide. High temperature influences photosynthetic function of plants by affecting the rate of chemical reactions and structural organization and conformational changes in enzymes. Photosynthetic response to temperature relies on plant species and growth conditions. C4 plants reveal high rates of photosynthesis at high temperature while C3 plants show greater photosynthesis efficiency at low temperature. In C3 plants, Rubisco activity is limited by CO2 concentration. In C4 plants, although rubisco activation is decreased at leaf temperatures above 32°C, the high level of CO2 in the mesophyll chloroplasts can counteract this effect until temperature approaches 40°C. Increased temperature will affect the physiological processes essential for crop growth and development of crops. If increases in temperature accompany increases in CO2 concentration, crop yields will decrease in regions where temperatures are below or above optimum. Future research should be directed toward identifying high-temperature tolerant crop cultivars that can produce more seeds under harsh climatic conditions. Keywords: Photosynthesis, C4, C3, Temperature DOI: 10.7176/JNSR/13-11-03 Publication date: June 30 th 2022