Maximum Net Assimilation Research Articles

Evaluation of Crop Establishment Methods and Nano Urea Versus Conventional Urea on Growth Indices in Rice Crop (Oryza sativa L.)

The present study aimed to evaluate Crop Establishment Methods and Nano Urea Versus Conventional Urea on Growth Indices in Rice Crop (Oryza sativa L.). Method of crop establishment influences the performance of rice through its effect on growth and development. Although, system of rice intensification has been reported to be the best establishment method. In traditional fertilizers, there is a huge loss of fertilizers by various manners like drift, leaching, runoff, microbial degradation, hydrolysis and photolysis. Bio accessibility of nutrients to plant is much lower relative to the rate of conventional fertilizers applied. The experiment was conducted during two consecutive seasons of Kharif 2022 and 2023 at the Agronomy Research Farm, Acharya Narendra Deva University of Agriculture & Technology, Kumarganj, Ayodhya (U.P.), India. The nitrogen level had significantly affected on crop growth rate, relative growth rate and net assimilation rate at all the stages of crop growth during both the years of investigations. The maximum Net assimilation rate at 30-60 and 60-90 DAS/DAT and crop growth rate, relative growth rate at 30-60, 60-90 and 90 to harvest DAS/DAT was recorded under 60% RDN through conventional Urea + 40% RDN through Nano Urea which was at par with 40% RDN through conventional Urea + 60% RDN through Nano Urea treatment, while significant over rest of the treatment during both the years of investigations.

Differential photosynthetic response to short- and long-term water deficit in Eucalyptus clones and hybrids with red gums

In Uruguay, there are more than a million hectares forested, and Eucalyptus species predominate. Drought events are becoming more frequent and affecting growth of the stands, especially during the early stages of the crop. Thus, the need arises to analyze the effects of such events on processes that determine growth, such as photosynthesis. The effect of water restriction on photosynthetic parameters was analyzed under greenhouse conditions in 6-months-old rooted cuttings of a clone of E. grandis (GG) and two hybrids with red gums: E. grandis × E. camaldulensis (GC) and E. grandis × E. tereticornis (GT). To define irrigation regimes water potential of substrate (MPa) was assessed using samples with increasing water content (%HR, w|w). Data was used to fit a water retention curve. Field’s capacity pot weight was determined on water drained pots. The control condition (WW) was established at Ψw = -0.15 MPa, while the water restricted (WR) was Ψw = -0.30 MPa. Treatments were maintained by manually water feeding for 16 weeks. Physiological parameters and photosynthetic pigments were recorded 6 and 16 weeks after water withholding to simulate short- and long-term water restriction scenarios, respectively. The following measurements were registered on current year fully expanded sun-exposed leaves: stomatal conductance (gs), maximum net assimilation rate (Amax), PSII quantum efficiency (FPSII), and proportion of chlorophyll and carotenoids in a HPLC elution (%Chl, %Carot). In the initial period, GG maintained Amax and gs between conditions. However, despite exhibiting lower gs in the restricted condition, GC maintained their Amax and GT increased in WR. There was no effect of treatment on photosynthetic pigments and energy partitioning varied little. At the end of the 16-week period, GG showed only decreased stomatal conductance values, and did not change photosynthetic pigment content nor Amax despite water restriction. Hybrids showed increasing values of FPSII, %Chl, and Amax. The PCA for long-term water restriction data showed that pigment content and FPSII may explain the increased assimilation rate of the hybrid clones under WR. Changes in water use efficiency due to higher % Chl in the restricted condition for both hybrids are discussed. There are few reports of increments in chlorophyll in Eucalyptus in drought. Recent information suggests that these types of strategies are adaptative responses that allow plants to cope with stress.

Effect of Organic Manures on Ideal Combinations for Maximum Onion (Allium cepa L.) Yield

A field experiment was conducted during winter season of 2021-22 at the Research Farm, AKS University, Satna (MP) to study the effect of organic manures on growth, yield and economics of onion (Allium cepa L.). Among the treatments, poultry manure 7 t/ha + vermicompost 10 t/ha (T12) recorded significantly maximum plant height, leaves/plant, neck diameter, leaf area index and crop growth rate (52.10 cm, 12.56/plant, 2.27 cm, 3.109 and 5.89 g/cm2/day, respectively) at 120 DAT. While, maximum relative growth rate (49.20 g/g/day) and net assimilation rate (1.435 mg/cm2/day) at 30 DAT in T12 was noted. T12 (poultry manure 7 t/ha + vermicompost 10 t/ha) also recorded the higher diameter and length of bulb (6.62 and 7.90 cm, respectively), bulb yield (42.31 t/ha) and net income (Rs 90282/ha) with 2.89 B:C ratio from onion var Agrifound Light Red.

Drivers of Decadal Carbon Fluxes Across Temperate Ecosystems.

Long-running eddy covariance flux towers provide insights into how the terrestrial carbon cycle operates over multiple timescales. Here, we evaluated variation in net ecosystem exchange (NEE) of carbon dioxide (CO2) across the Chequamegon Ecosystem-Atmosphere Study AmeriFlux core site cluster in the upper Great Lakes region of the USA from 1997 to 2020. The tower network included two mature hardwood forests with differing management regimes (US-WCr and US-Syv), two fen wetlands with varying levels of canopy sheltering and vegetation (US-Los and US-ALQ), and a very tall (400m) landscape-level tower (US-PFa). Together, they provided over 70 site-years of observations. The 19-tower Chequamegon Heterogenous Ecosystem Energy-balance Study Enabled by a High-density Extensive Array of Detectors 2019 campaign centered around US-PFa provided additional information on the spatial variation of NEE. Decadal variability was present in all long-term sites, but cross-site coherence in interannual NEE in the earlier part of the record became weaker with time as non-climatic factors such as local disturbances likely dominated flux time series. Average decadal NEE at the tall tower transitioned from carbon source to sink to near neutral over 24years. Respiration had a greater effect than photosynthesis on driving variations in NEE at all sites. Declining snowfall offset potential increases in assimilation from warmer springs, as less-insulated soils delayed start of spring green-up. Higher CO2 increased maximum net assimilation parameters but not total gross primary productivity. Stand-scale sites were larger net sinks than the landscape tower. Clustered, long-term carbon flux observations provide value for understanding the diverse links between carbon and climate and the challenges of upscaling these responses across space.

Growth analysis and grain yield of rice (Oryza sativa L.) varieties under green manure based integrated nutrient management

Field experiments were conducted at Bhubaneswar, Odisha during kharif seasons of 2018 and 2019 to study the growth behavior of rice varieties under nutrient management practices. Six treatment combinations comprising of three nutrient management (100% Soil Test Based Nitrogen Recommendation (STBNR), 75% STBNR + in situ green manuring (dhaincha) and 50% STBNR + in situ green manuring of dhaincha) and two rice varieties (Manaswinee of 125d duration and Hasanta of 145d duration) were tried in randomized complete block design (RCBD) with four replications. The results showed that crop growth rate (CGR) was significantly influenced by both nutrient management practices and varieties. Pooled over the years, application of 75% STBNR + green manuring of dhaincha exhibited the maximum CGR of 11.33 and 20.80 g/m2/day during 30-60 and 60-90 DAT, respectively and which were superior to 100% STBNR and 50% STBNR + green manuring of dhaincha. Similarly, rice cv. ‘Hasanta’ recorded CGR of 10.98 and 20.42 g/m2/day during 30-60 and 60-90 DAT, respectively, which were higher over cv. ‘Manaswinee’. The maximum relative growth rate (RGR) of 23.77 mg/g/day was registered with 50% STBNR + green manuring of dhaincha, being at par with 75% STBNR + green manuring of dhaincha during 60-90 DAT. Application of 75% STBNR + green manuring of dhaincha recorded the maximum Net assimilation rate (NAR) of 3.41 and 4.26 g/m2 leaf area/day during 30-60 and 60-90 DAT, respectively. Both cultivars were equally effective for RGR and NAR. The treatment trend for physiological indices led to higher grain yield under 75% STBNR + green manuring of dhaincha among nutrient management practices and cv. ‘Hasanta’ between rice varieties. Grain yield and the three physiological indices were positively correlated, but the correlation coefficient values were significant for CGR and NAR.

Growth analysis and grain yield of rice (Oryza sativa L.) varieties under green manure based integrated nutrient management

Field experiments were conducted at Bhubaneswar, Odisha during kharif seasons of 2018 and 2019 to study the growth behavior of rice varieties under nutrient management practices. Six treatment combinations comprising of three nutrient management (100% Soil Test Based Nitrogen Recommendation (STBNR), 75% STBNR + in situ green manuring (dhaincha) and 50% STBNR + in situ green manuring of dhaincha) and two rice varieties (Manaswinee of 125d duration and Hasanta of 145d duration) were tried in randomized complete block design (RCBD) with four replications. The results showed that crop growth rate (CGR) was significantly influenced by both nutrient management practices and varieties. Pooled over the years, application of 75% STBNR + green manuring of dhaincha exhibited the maximum CGR of 11.33 and 20.80 g/m2/day during 30-60 and 60-90 DAT, respectively and which were superior to 100% STBNR and 50% STBNR + green manuring of dhaincha. Similarly, rice cv. ‘Hasanta’ recorded CGR of 10.98 and 20.42 g/m2/day during 30-60 and 60-90 DAT, respectively, which were higher over cv. ‘Manaswinee’. The maximum relative growth rate (RGR) of 23.77 mg/g/day was registered with 50% STBNR + green manuring of dhaincha, being at par with 75% STBNR + green manuring of dhaincha during 60-90 DAT. Application of 75% STBNR + green manuring of dhaincha recorded the maximum Net assimilation rate (NAR) of 3.41 and 4.26 g/m2 leaf area/day during 30-60 and 60-90 DAT, respectively. Both cultivars were equally effective for RGR and NAR. The treatment trend for physiological indices led to higher grain yield under 75% STBNR + green manuring of dhaincha among nutrient management practices and cv. ‘Hasanta’ between rice varieties. Grain yield and the three physiological indices were positively correlated, but the correlation coefficient values were significant for CGR and NAR.

Photosynthetic Physiology Comparisons between No Tillage and Sod Culture of Citrus Farming in Different Seasons under Various Light Intensities

Sod culture (SC) and no tillage (NT) are modern orchard management systems, and are two different bases for the sustainable development and production of citrus orchards in Taiwan. However, there is no information about the efficiency of either NT or SC on the photosynthetic physiology of farmed citrus under different seasons and varying light intensities. The objective of this study was to clarify the impacts of SC and NT under eco-friendly farming management on the photosynthetic apparatus of an important plantation citrus species in response to varying light intensities over the seasons. The results showed that Rd (dark respiration rate of CO2), Qy (light quantum yield of CO2), LCP (light compensation point), Amax (maximum net assimilation of CO2), and Fv/Fm values of citrus plants under SC were somewhat higher under NT in the same season, particularly in the fall and in winter. As light intensity increased from 200 to 2000 μmol photon m−2 s−1 PPFD, higher Pn (net photosynthesis rate), Gs (stomatal conductance), ETR (electron transport rate), NPQ (non-photochemical quenching), and Fv/Fm (potential quantum efficiency of PSII) values were observed in spring and summer compared to the fall and winter, and increasing NPQ and decreasing Fv/Fm values were observed in all seasons. Positive and significant correlations were shown between the Pn and Gs under NT and SC in all seasons with all light illuminations, whereas significant and negative relationships were observed between the ETR and NPQ under NT in fall and winter at 1200~2000 PPFD. In short, ETR was useful for non-destructive estimations of Pn and NPQ since these indices were significantly and positively correlated with ETR in citrus leaves exposed to 0~1200 PPFD in all seasons and 1200~2000 PPFD in spring, the fall, and winter, providing a quick means to identify the physiological condition of plants under various seasons and tillages. The precise management of photosynthetic parameters such as ETR in response to light irradiances under varied seasons also provides implications for sustainable citrus production for tillage cropping systems in future higher CO2 and potentially wetter or drier environments. The tillages may hold promise for maximizing the economic efficiency of the growth and development of citrus plants grown in the field.

How Do Different Cocoa Genotypes Deal with Increased Radiation? An Analysis of Water Relation, Diffusive and Biochemical Components at the Leaf Level

The cultivation of cocoa (Theobroma cacao L.) is traditionally managed under shade because of its photosynthetic characteristics; however, its behavior can vary according to the genotype and environmental conditions where it is grown. In this sense, here, we explore the possible mechanisms of protection against radiation stress and how these mechanisms are affected by variation between cocoa genotypes. Therefore, we evaluate the effect of the radiation level (HPAR, 2100 ± 46 mol m−2 s−1; MPAR, 1150 ± 42 mol m−2 s−1; LPAR, 636 ± 40 mol m−2 s−1) on the water status and gas exchange in plants of different cocoa genotypes (CCN-51, ICS-1, ICS-95, LUKER-40 and LUKER-50), and the occurrence of photoinhibition of PSII (as a marker of photodamage), followed by a characterization of the protection mechanisms, including the dynamics of photosynthetic pigments and enzymatic and non-enzymatic antioxidant systems. We found significant changes in the specific leaf area (SLA) and the water potential of the leaf (ΨL) due to the level of radiation, affecting the maximum quantum yield of PSII (Fv/Fm), which generated dynamic photoinhibition processes (PIDyn). Cocoa genotypes showed the lowest Light-saturated maximum net carbon assimilation rate (Amax) in HPAR. Moreover, the maximum carboxylation rate (Vcmax) was negatively affected in HPAR for most cocoa genotypes, indicating less RuBisCO activity except for the ICS-95 genotype. The ICS-95 showed the highest values of Vcmax and maximum rate of regeneration of ribulose-1,5-bisphosphate (RuBP) controlled by electron transport (Jmax) under HPAR. Hence, our results show that some genotypes were acclimated to full sun conditions, which translated into greater carbon use efficiency due to the maximization of photosynthetic rates accompanied by energy dissipation mechanisms.

파종 시기에 따른 잇꽃의 생장 특성과 건물생산성

Background: Safflower (Carthamus tinctorius L.) is a useful medicinal crop in Korea. The optimal sowing time in the central region is mid-March. This study was conducted to determine the growth characteristics according to the sowing period and number of days after sowing. This basic data would be useful in cultivating safflower.<BR>Methods and Results: Starting in mid-March, plants were sown 10 times at 15-day intervals. Thirty plants were harvested from day 30. The dry weight and leaf area were measured. The seed yield was surveyed at the time of the final harvest. Maximum relative growth rate (RGR) and net assimilation rate (NAR) were observed in the early growth phase. Among the growth analysis characteristics, the crop growth rate (CGR) of individual plants and leaf area index (LAI) of canopy were highest during the flowering period. The seed yield was highest in the fourth sowing treatment phase (April-16th). The seed germination rate was high in the first and second sowing treatments phase (March-16th and April-1st) due to seed decay during the rainy season.<BR>Conclusions: Considering the rate of seed decay and germination, it is important to sow as early as possible in the first sowing treatment phase (March-1st) and harvest before the rainy season.

IMPACT OF FOLIAR APPLICATION OF POTASSIUM SULPHATE ON WEED DYNAMICS AND SOME PHYSIOLOGICAL ATTRIBUTES OF RAINFED BREAD WHEAT

An experiment to find out the wheat growth as affected by foliar application of potassium Sulphate (K2SO4) on different growth stages under rainfed conditions was conducted at the Agricultural Research Institute, Dera Ismail Khan, Pakistan. Potassium doses viz. 0, 12, 18, 24, 30 and 60 kg ha-1 were applied in foliar form at tillering, booting and heading stages of wheat. The course of study revealed that foliar application of K2O in booting stage produced maximum leaf area index (LAI), leaf area duration (LAD), crop growth rate (CGR), net photosynthesis rate (NPR) and grain yield, while its application at heading stage produced maximum net assimilation rate (NAR). Among different doses, the application of potassium at the rate of 60 kg ha-1 potassium at the rate of 60 kg ha-1 produced maximum growth and yield and its components during two consecutive cropping seasons of wheat crop while weed density (m-2), relative weed density (%), fresh weed biomass (g m-2) and dry weed biomass (g m-2) influenced non-significantly for both the years. These findings suggest that foliar application of potassium sulphate @ 60 kg ha-1 along with recommended dose of nitrogen (120 kg ha-1) and phosphorus (90 kg ha-1) is the most suitable for successful wheat production under rainfed conditions.

Open field experiment for the evaluation of Arundo donax ecotypes ecophysiology and yield as affected by soil water content

The high photosynthetic efficiency and the drought tolerance of Arundo donax L. contribute to its potential use as a suitable biomass crop for drought prone environments.A modelling approach to study net assimilation and stomatal conductance as influenced by available soil water content (ASWC) can be used to obtain threshold values to support the management of irrigation practice.Physiological model parameters, morphological (stem height and max diameter, number of leaves per stem), and productive traits (yield and biomass ash content), can support ecotypes selection activity, crucial for genetic improvement in a crop, such as A. donax, widely distributed in natural habitats, but characterized by no viable seeds.To this end, an open field experiment has been conducted comparing three A. donax L. clones collected from habitats representing a gradient of increasing temperature and declining water availability (Morocco; South Italy, and North Italy). Two irrigation treatments (rain-fed, and well-watered) and two different harvest dates (December and March) were also imposed as experimental factors.Physiological model involved light response curve approach measuring net assimilation and stomatal conductance under different light intensity and different actual ASWC. The obtained physiological curve parameters in relation to ASWC (maximum net assimilation - AN-sat, photosynthetic quantum efficiency - Qapp, and maximum stomatal conductance - Gs-sat) were well fitted by a two-segmented piecewise regressions. The segment breakpoints were computed at 43%, 39% and 65% of ASWC, for AN-sat, Qapp, and Gs-sat, respectively. This means that between 65% and 43% of ASWC, only stomatal conductance appeared to be influenced by the decrease of ASWC, reducing stomata opening, whereas the efficiency of net assimilation resulted unaffected by water depletion. The capacity to sustain high net assimilation rates untill low ASCW and the capacity to full recover net photosynthesis after a severe drought stress, emerged as crop traits contributing to explain the drought resistant aptitude of A. donax. No differences have been reported for any of the studied physiological parameters within ecotypes. On the contrary, the three clones exhibited differences in terms of biometric characters, biomass production and its ash content. The results of the study emphasize the multipurpose value of Moroccan ecotype reporting best performances in terms of both quantity and quality (highest biomass yield - 26.4 t ha−1 - lowest ash content 4.8%).

UV Light Acclimation Capacity of Leaf Photosynthetic and Photochemical Behaviour in Near-isohydric and Anisohydric Grapevines in Hot and Dry Environments

The photosynthetic and photochemical adaptation of grapevine leaves to high UV radiation, under hot and dry summer conditions, was investigated in near-isohydric Cannonau (syn. Grenache) and nearanisohydric Bovale grande (syn. Carignan). From pea-size stage until harvest, vines with mild to moderate water deficit were subjected to UV-blocking treatment (–UV) and compared to a control exposed to sunlight (C). Canopy light and thermal microclimate, growth and density, maximum leaf gas exchange, primary photochemistry (PSII) and phenols were monitored. Average increments in canopy temperature under –UV tunnels during day-time and night-time were 3.3°C and 0.8°C in Bovale grande and 2.6°C and 1.1°C in Cannonau. Cultivars reached similar leaf area, intrinsic water-use efficiency and stem water potential under C and –UV. Cannonau showed lower stomatal conductance, maximum net assimilation and transpiration rates, but also faster recovery of PSII under heat and moderate water stress. UV radiation induced a stronger and longer impact on leaf assimilation, but the duration of elevated temperatures under −UV induced higher photoinhibition and lower photochemical efficiency. A similar degree of correlation between leaf temperature and gas exchange was found among cultivars and treatments. In Cannonau, leaf anthocyanin decreased due to heat-induced long-lasting PSII photoinactivation under C. Conversely, Bovale grande showed higher phenolic content stability, thus higher photoprotection and recovery of PSII functional units. Agronomical practices affecting leaf phenolic accumulation influence canopy acclimation to heat and high sunlight. Vineyard management must avoid excessive canopy sun exposure and duration of elevated temperatures to favour high assimilation, while reducing photoinactivation and heat damage.

Shade-tolerance of seedlings of rain-forest trees: monodominants vs. subordinates and episodic vs. continuous regenerators

Abstract:Several monodominant rain-forest trees in New Caledonia have population size structures suggesting establishment following large-scale disturbance, with eventual replacement by shade-tolerant species predicted in the absence of future disturbance. Links of dominance and population dynamics to leaf-level photosynthesis were investigated in seedlings of 20 tree species from these forests, grown in experimental sun and shade conditions. In particular, we tested whether episodically regenerating (ER) species, including monodominants, have higher assimilation rates at high irradiances and lower tolerance of shade than continuously regenerating species (CR). ER species had higher maximum net assimilation rates (Amax-area) in sun plants (9.6 ± 0.4 μmol m−2 s−1) than CR species (6.2 ± 0.3 μmol m−2 s−1) and high plasticity, typical of shade-intolerant species, but monodominant species did not differ from other ER species. CR species had leaf-level traits consistent with shade tolerance, including lower dark respiration rates (Rd-area = 0.47 ± 0.03μmol m−2 s−1; Rd-mass = 7 ± 1 nmol g−1 s−1) than ER species (Rd-area = 0.63 ± 0.06 μmol m−2 s−1; Rd-mass = 11 ± 2 nmol g−1 s−1) in shade plants. Hence leaf-level assimilation traits were largely consistent with regeneration patterns, but do not explain why some shade-intolerant species can achieve monodominance.

Convergence in resource use efficiency across trees with differing hydraulic strategies in response to ecosystem precipitation manipulation

Summary Plants are expected to respond to drought by maximizing the efficiency of the most limiting resource, the water use efficiency (WUE), at the expense of nitrogen and carbon use efficiencies (NUE and CUE). Therefore, plants resource use efficiencies are viewed as indicators of species drought tolerance. We tested these predictions by measuring leaf‐level intrinsic WUE (WUEi, the ratio of net assimilation to stomatal conductance), photosynthetic NUE (PNUE, the ratio of daily maximum net assimilation to leaf nitrogen content) and leaf‐scale CUE (approached by the ratio of night‐time respiration to daytime net assimilation, Rd/An) in piñon pine and juniper, two tree species that differ in drought tolerance and vulnerability to drought‐induced mortality. Variations in resource use efficiency in the two species were measured in response to seasonal drought and in response to an ecosystem‐scale precipitation manipulation experiment comprising three precipitation treatments: ambient, irrigation (+30%) and partial rainfall exclusion (−45%). Increasing water limitation, either seasonally or across treatments, resulted in increased WUE and decreased PNUE and CUE in both species. WUE, PNUE and CUE varied more strongly in response to water limitation than across species and converged to the same relationships against precipitation for piñon and juniper. Plasticity in WUE, PNUE and CUE in response to water limitation was associated, in both species, with low carbon acquisition during drought. Our results exhibited a convergence in resource use efficiency across piñon and juniper which contradicts the paradigm that resource use efficiencies are indicators of species drought tolerance and ecological strategy.

English

Salinity is one of the most important factors limiting growth and development in cultivated species. Kentucky bluegrass was grown in boxes filled with sand (100%), 95% sand: 5% zeolite, 90% sand: 10 % zeolite and 85% sand 15% zeolite (V/V). Poa pratensis plants were irrigated with 0.24, 3.4 and 6.4 dS.m -1 salt water daily for 6 months in greenhouse condition to study the effect of different levels of zeolite on turf quality (TQ) and some physiological growth factors, salt deposition, sodium absorption ratio (SAR) and ion composition in leachate under different levels of salinity. Saline water reduced (PR), transpiration, (SC), (ME), (WUE), maximum assimilation rate (Amax), carboxylation efficiency (g , m) and net assimilation rate (A360) compared to control. Amendment of sand with zeolite increased TQ, PR, transpiration, SC, ME, WUE, (Amax), (g , m) and (A360) during both the 2nd & 3rd months at both salinity levels. Highest effect obtained in highest percent of zeolite. The beneficial effects of zeolite on turf quality and other parameters diminished 3 months after treatments. Amendment of sand with zeolite reduced leaching of Na and K but, increased leaching of Ca and Mg. Using zeolite in medium increased SAR value compared to control. Results indicate that amending with zeolite may buffer soil solution Na concentration in short-term. In the long-term, however, a substantial amount of Na may be retained concurrent with Ca & Mg exchange, thereby increasing sodicity & salinity problems.

The effect of plant population on growth parameters and seed yield of faba bean

In order to study the effect of density and cultivars on growth physiological indexes affecting grain yield of faba bean, field experiment was carried out in the city of Ahwaz field healthy martyr in a factorial randomized complete block design with four replications in crop year of 2011-2012. These factors include density at three levels (8, 12, 16 plants per square meter) and three varieties (Barekat, Saraziri, local varieties dezful ), respectively. The results showed that the average density of 12 per square meter with 49.478 grams per square meter, grain yield was significantly increased compared with the average barekat76.535 grams per square meter than other cultivars had the highest grain yield. Survey results showed that treatments affected plant growth and physiological parameters were compared. LAI highest number and density of 16 plants m barekat obtained. CGR maximum density of 12 plants per square meter ofleaf area index was more in barekat digits. Maximum net assimilation rate on leaf area due to larger numbers and more barekat and density of 8 per square meter, respectively almost the same trend of relative growth rate of the trend followed.

Effects of soil water and nitrogen availability on photosynthesis and water use efficiency of Robinia pseudoacacia seedlings

The efficient use of water and nitrogen (N) to promote growth and increase yield of fruit trees and crops is well studied. However, little is known about their effects on woody plants growing in arid and semiarid areas with limited water and N availability. To examine the effects of water and N supply on early growth and water use efficiency (WUE) of trees on dry soils, one-year-old seedlings of Robinia pseudoacacia were exposed to three soil water contents (non-limiting, medium drought, and severe drought) as well as to low and high N levels, for four months. Photosynthetic parameters, leaf instantaneous WUE (WUEi) and whole tree WUE (WUEb) were determined. Results showed that, independent of N levels, increasing soil water content enhanced the tree transpiration rate (Tr), stomatal conductance (Gs), intercellular CO2 concentration (Ci), maximum net assimilation rate (Amax), apparent quantum yield (AQY), the range of photosynthetically active radiation (PAR) due to both reduced light compensation point and enhanced light saturation point, and dark respiration rate (Rd), resulting in a higher net photosynthetic rate (Pn) and a significantly increased whole tree biomass. Consequently, WUEi and WUEb were reduced at low N, whereas WUEi was enhanced at high N levels. Irrespective of soil water availability, N supply enhanced Pn in association with an increase of Gs and Ci and a decrease of the stomatal limitation value (Ls), while Tr remained unchanged. Biomass and WUEi increased under non-limiting water conditions and medium drought, as well as WUEb under all water conditions; but under severe drought, WUEi and biomass were not affected by N application. In conclusion, increasing soil water availability improves photosynthetic capacity and biomass accumulation under low and high N levels, but its effects on WUE vary with soil N levels. N supply increased Pn and WUE, but under severe drought, N supply did not enhance WUEi and biomass.

Nutritional status of Abies pinsapo forests along a nitrogen deposition gradient: do C/N/P stoichiometric shifts modify photosynthetic nutrient use efficiency?

Chronic atmospheric N deposition has modified relative N availability, altering the biogeochemical cycles of forests and the stoichiometry of nutrients in trees, inducing P limitation, and modifying the N:P ratios of plant biomass. This study examines how the variation in the foliar stoichiometry of Abies pinsapo across an N deposition gradient affects foliar traits and photosynthetic rate. We measured the maximum net assimilation rates (Amax) and the foliar nitrogen (N) and phosphorus (P) concentrations in A. pinsapo needles of five age classes. The leaf mass per area and photosynthetic N and P use efficiencies (PNUE and PPUE, respectively) were also estimated. The results from the N-saturated stand (Sierra Bermeja, B) differed from the comparable N-limited stands under investigation (Yunquera, Y, and Sierra Real, SR). The trees from Y and SR exhibited a reduction in the N content in older needles, whereas the foliar N concentration at the B site increased with needle age. N and P were positively correlated at Y and SR, but not at B, suggesting that the overload of N in the trees at site B has exceeded the homeostatic regulation capacity of the N-saturated stand in terms of foliar stoichiometry. A max and PNUE were correlated positively with P and negatively with the N/P ratio at the three study sites. The foliar N concentration was positively correlated with A max at Y and SR. However, this relationship was negative for the B site. These findings suggest that the nutritional imbalance caused by increased chronic deposition of N and an insufficient supply of P counteracts the potential increase in net photosynthesis induced by the accumulation of foliar N.

Effects of experimental warming on phenology, growth and gas exchange of treeline birch (Betula utilis) saplings, Eastern Tibetan Plateau, China

Mountain birch (Betula utilis) is the most important treeline species in alpine forests of southwestern China. In order to understand the effects of future warming on treeline birch, this study was conducted to examine the effects of experimental warming on leaf phenology, growth and gas exchange of B. utilis saplings using the open top chamber (OTC) method in a treeline ecotone of eastern Tibetan Plateau. The OTCs enhanced daily mean air temperature by 2.9 K throughout the growing season. Conversely, soil moisture within the OTCs on average declined by 3% over the experimental period. Experimental warming did not affect the timing of bud break, although treeline birch saplings growing in the OTCs manifested later leaf abscission, resulting in longer leaf life span. Artificial warming significantly accelerated the leaf and shoot growth rates of treeline birch saplings, resulting in larger leaf area and longer shoot elongation late in the growing season. Moreover, experimental warming significantly reduced the leaf fluctuating asymmetry (FA) and tended to increase specific leaf area (SLA). Moreover, elevated temperatures significantly enhanced the transpiration rate (E), stomatal conductance (g s), maximum net assimilation rate (A max), dark respiration rate (R d) and apparent quantum yield (AQY) but did not influence the light compensation point (LCP) and light saturation point (LSP) of treeline birch saplings. Taken together, our results indicated that short-term experimental warming markedly altered structural/functional leaf traits and enhanced photosynthetic capacity of treeline birch saplings; such positive responses in treeline birch would be favorable for the growth of this species under future warmer world.

Nondestructive determination of nitrogen and chlorophyll content in olive tree leaves and the relation with photosynthesis and fluorescence parameters

For Tunisian olive tree orchards, nitrogen deficiency is an important nutritional problem, in addition to the availability of water. Establishment of relationships between nutrients such as nitrogen and ecophysiological parameters is a promising method to manage fertilisation at orchard level. Therefore, a nitrogen stress experiment with one-year-old olive trees (Olea europaea L. ‘Koroneiki’ and ‘Meski’) was conducted with trees respectively subjected to four nitrogen supply regimes (23.96 meq l−1, 9.58 meq l−1, 4.79 meq l−1 and 0 meq l−1 NO3 −1). The current paper focuses on the use of the SPAD-502 portable chlorophyll (Chl) meter, a nondestructive method for fertilisation management under nitrogen stress conditions of olive trees. Maximum net photosynthetic assimilation rates, chlorophyll fluorescence parameters and the SPAD Chl index were therefore measured simultaneously and the Chl and nitrogen content of the leaves were analysed. Significant correlations were established in the olive tree leaves between SPAD-502 readings on the one hand and Chl content, nitrogen content, photosynthetic assimilation rate, and Chl fluorescence parameters (ΦPSII and ETR) on the other hand.