Net Assimilation Rate Research Articles

Assessing the Role of Crop Rotation in Shaping Foliage Characteristics and Leaf Gas Exchange Parameters for Winter Wheat

Properly designed crop rotation enriches the diversity of the agroecosystem, which has a favorable effect on the environmental properties and crop yield. The experiment assessed winter wheat cultivated under the following crop rotations: A. winter rape + catch crop − spring barley − field pea − winter wheat; B. winter rape − winter wheat + catch crop − field pea − winter wheat; C. winter rape + catch crop − field pea − winter wheat − winter wheat; D. winter rape − winter wheat + catch crop − spring barley − winter wheat. The aim of the study was to investigate: (i) whether the cultivation of wheat in crop rotations following forecrops of rape, pea, barley, and wheat will affect its foliage and photosynthesis; (ii) how the photosynthetic process will affect the wheat yield. At the stem elongation stage (BBCH 36) and at the heading stage (BBCH 58), the following were investigated: foliage features, photosynthetic parameters, and the above-ground biomass; while at the BBCH 89 stage, the grain yield was investigated. It was demonstrated that photosynthesis was most intense under crop rotation A (the highest stomatal conductance, transpiration, intercellular CO2 concentration, and net assimilation rate ranged from 13.1–29.7 μmol CO2∙m−2·s−1). This was reflected in the above-ground biomass volume (1245–1634 g m−2) and grain yield (4.58–7.65 t ha−1). The cultivation of wheat following wheat under crop rotation C and following barley under D had a negative effect on both the foliage and photosynthetic parameters.

Foliar application of putrescine alleviates terminal drought stress by modulating water status, membrane stability, and yield- related traits in wheat (Triticum aestivum L.).

Drought stress is one of the major limitations to the growth and yield productivity of cereal crops. It severely impairs the early growing and grain -filling stages of wheat. Therefore, cost- effective and eco-friendly approaches for alleviating drought stress in cereal crops are in high demand. Polyamines, such as putrescine, have a significant effect on improving crop yield under drought- stress conditions. Therefore, the current study was executed with the aim of exploring the significance of putrescine in alleviating drought stress and improving yield- related traits in wheat. Two distinct wheat cultivars (Fakhar-e-Bhakkar and Anaj-2017) were treated with the foliar application of different concentrations (control, 0.5, 1.0, and 1.5 PPM) of putrescine (put) under two moisture conditions (well- watered and terminal drought stress). The results demonstrate that the imposition of terminal drought stress significantly reduces different physiological and yield- related traits of both wheat cultivars. The reduction of relative water content (RWC%), membrane stability index (MSI), leaf area, tillers per plant, biomass yield, number of spikelets per spike, 100-grain weight, grain yield per plant, and straw yield was greater in Anaj-2017 than in Fakhar-e-Bhakkar cultivar. The results further explain that the foliar application of increased concentrations of putrescine from 0.0 to 1.0 PPM gradually improved physiological and yield traits, whereas these traits declined with the application of putrescine at the highest dose (1.5 PPM). The exogenous application of 1.0 PPM putrescine improved the relative water content (19.76%), specific leaf area (41.47%), and leaf area ratio (35.84%) compared with the controlled treatment. A higher grain yield (28.0g plant-1) and 100-grain weight (3.8g) were obtained with the foliar application of 1.0 PPM putrescine compared with controlled treatments. The findings of this study confirm the protective role of putrescine against terminal drought stress. It is therefore recommended to use putrescine at a concentration of 1.0 PPM, which could help alleviate terminal drought stress and attain better wheat yield.

Physiological and Nutritional Responses of Ungrafted Merlot and Cabernet Sauvignon Vines or Grafted to 101-14 Mgt and 1103P Rootstocks Exposed to an Excess of Boron

The aim of this study is to analyze the effect of excess boron (B) on the nutrient uptake, growth, and physiological performance of grapevines. Merlot and Cabernet Franc grapevines, either own-rooted or grafted onto 1103P and 101-14 Mgt rootstocks, were exposed in a hydroponic pot experiment to 0.5 mM boron for sixty days. Twenty-five days following the beginning of B treatment, the first symptoms of boron toxicity appeared, including leaf edge and margin yellowing, subsequent necrosis, and cupping of leaf blades. At harvest, sixty days after the start of the experiment, B concentration of the treated vines increased in all parts of the vine in the following order: Leaves > Roots > Trunks > Shoots. Leaf Boron concentration in treated vines ranged from 980.67 to 1064.37 mg kg−1 d.w. Boron excess significantly reduced the concentrations of all macro and micronutrients studied in this experiment. The total leaf chlorophyll (Chl) concentration decreased from 35.46 to 44.45%, thirty and sixty days, respectively, from the beginning of the boron treatments. In addition, an excess amount of boron resulted in a dramatic decrease in net CO2 assimilation rate, stem water potential, and PSII maximum quantum yield, irrespective of vine type (own-rooted or grafted). At the end of the experimental period, the total leaf phenolic content increased by 71.73% in Merlot and by 71.16% in Cabernet Franc due to Boron stress. The tressed vines grafted onto 1103P showed increased shoot and root dry weights, leaf chlorophyll content, CO2 assimilation rates, and Fv/Fm ratio compared to vines grafted onto 101-14 Mgt. It was found that rootstocks play an important role in B toxicity. The results showed that the leaf accumulation of boron was delayed to a greater extent by 1103P rootstock compared to 101-14 Mgt, resulting in the earlier appearance of leaf toxicity symptoms in vines grafted onto 101-14 Mgt rootstock compared to 1103P.

Increasing the growth and yield of shallot (Allium cepa L. Aggregatum group) by using Methyl Jasmonic Acid (MeJA) concentrations under drought condition

Drought is one of the limiting factors for plant production, and there is a continuous demand for drought tolerant plants. Shallots are considered a shallow-rooted crop and have been reported to have little tolerance to drought conditions. One of the efforts to increase plant tolerance to drought conditions is through the addition of Methyl Jasmonic Acid (MeJA). MeJA is involved in several physiological and biochemical procedures in plant growth and development. Application of MeJA can increase the plant tolerance to drought conditions through chlorophyll synthesis, stomatal conductivity, transpiration, net photosynthetic rate and biomass production. This research was conducted in a complete randomized block design with three replications to determine the response of shallot plants to the application of MeJA (0 µM, 25 µM, 50 µM and 100 µM) under drought conditions, which was simulated through the frequency of watering (once daily, every other day, once in three days). Soil water content calculated before the watering treatment was 24.45%, 20.34% and 18.45% for watering once daily, every other day, once in three days, respectively. The results showed that the addition of MeJA played a role in enhancing the growth and productivity of shallot plants under normal and drought conditions. Application of 50 µM of MeJA could increase the Water Use Efficiency, maintain the Relative Water Content, increase the width of stomatal aperture, and increase the leaf area and Leaf Area Index. This also led to increasing Net Assimilation Rate and Plant Growth Rate. Application of 50 µM of MeJA gave in increasing bulb productivity and reached 7.86 ton.ha-1, which was 58.2 % higher than that of in control (without MeJA application). Application of MeJA to shallot plants exhibited avoiding type of physiological tolerance.

Water stress influence of Rajendrasonia and Pitamber turmeric varieties

Turmeric varieties viz., Rajendrasonia and Pitamber were subjected to water stress by irrigating at different intervals. Impact of water stress on morphological, physiological and yield parameters of both the varieties were investigated. In this study irrigation treatments divided into three groups. Group A, control receives water weekly once. For every two weeks once group B was irrigated and for every three weeks once group C was irrigated. Plants which are under heavy water stress showed gradual reduction in morphological, physiological and yield parameters, i.e. plant height, number of leaves, leaf area, leaf area index, Net Assimilation rate, Relative Growth rate , fresh and dry weight of rhizome. Pitamber and Rajendrasonia growth parameters, physiological and yield parameters were slightly affected in moderate stress compared to control. In heavy stress condition the two varieties severely affected compared to control and moderate stress. Among the two selected varieties Pitamber was less affected in all parameters except in leaves number, tuberous roots length and in dry weight in moderate and heavy stress.

Initial development of maize plants grown with different combinations of nitrate and ammonium

Corn is one of the main commodities of Brazilian agribusiness, due to its wide use, whether for human or animal consumption or in the chemical and biofuel industries. Thus, this work was carried out to evaluate the influence of different proportions of nitrate and ammonium in the initial development of corn plants. The experiment took place in a greenhouse, by direct sowing, where the seeds were placed at a depth of 1 cm in plastic pots with a capacity of 6 dm3 containing a mixture of previously sieved and washed with vermiculite, in a 2:1 ratio. Five proportions of nitrate and ammonium ions (NO3- :NH4+) were used: T1=100:0, T2=75:25, T3=50:50, T4=25:75 and T5=0:100, through nutrient solutions. After 35 days of cultivation, the following were evaluated: plant height, number of leaves, culm diameter, chlorophyll a, b, total and a/b ratio, root length, leaf fresh matter mass, dry matter mass of leaves, culm, roots, total dry mass, and root dry mass/shoot dry mass ratio, leaf area, specific leaf area, leaf area ratio, and leaf mass ratio. Nitrate as the only source of nitrogen provided a smaller increase in the chlorophyll a index of maize plants, which is the most important chlorophyll in the capture of light in the antenna complex. It is not recommended to cultivate corn plants with only nitrate or ammonium; however, it was observed that high doses of nitrate combined with low doses of ammonium in the culture medium provided satisfactory performance for most variables.

Effect of coconut husk organic fertilizer from liquid organic fertilizer waste on growth and yield eggplant (Solanum melongena L.)

The objective of the study was to determine the effect of using coconut husk organic fertilizer from liquid organic fertilizer waste on the growth and yield of eggplant. The factors of the experiment were; P0 = 0 tons ha-1coconut husk organic fertilizer from liquid organic fertilizer waste, P1 = 7 tons ha-1coconut husk organic fertilizer from liquid organic fertilizer waste, P2 = 14 tons ha-1 coconut husk organic fertilizer from liquid organic fertilizer waste, P3 = 21 tons ha-1coconut husk organic fertilizer from liquid organic fertilizer waste arrange as a randomized block design factorial. The results show that the doses of coconut husk organic fertilizer from liquid organic fertilizer waste 21 tons ha-1 gives a higher fruit weight of 69.97 tons ha-1. The lowest result is without the provision of coconut husk organic fertilizer from liquid organic fertilizer waste with a weight of 52.87 tons ha-1. In addition, there is a significant relationship between the rate of plant growth and the rate of net assimilation (r= 0.90**) and the weight of fruit weight per hectare (r= 0.51**). This study revealed that the application of coconut husk organic fertilizer from liquid organic fertilizer waste at high doses could increase the growth and yield of eggplant.

The morphophysiological mechanisms of light-induced net primary production of Amazonian tree species

We investigated the morphophysiological mechanisms indicative of resource uses behind net primary production in seedlings of three valuable forest species of socio-economic value in the Amazon:mahogany (Swietenia macrophylla), Brazil nut (Bertholletia excelsa) and Laurel (Cordia alliodora). The hypotheses tested were: (i) the three species will grow better under mild to high light but with different magnitudes of response; and (ii) the three species will show different mechanisms to reach a better growth under mild to high light We measured biomass production and a set of morphophysiological leaf traits and calculated the relative growth rates (diameter and height) of seedlings subjected to low(0.9), moderate (11.3) and high (45.0 mol m-2 day-1) irradiance for 80 days. For all species, biomass and growth increase with irradiance and the magnitude of the effect were species-dependent. The changes in total biomass by irradiance varied 1.5-fold (B. excelsa) and twofold (S. macrophylla). Light-induced changes in biomass partitioning and morphophysiological traits varied among species. S. macrophylla and C. alliodora significantly increased root/aboveground mass ratio (R/A) under high irradiance. Gas exchange increased with irradiance for C. alliodora and B. excelsa. The non-structural carbohydrates of C. alliodora and S. macrophylla were greater in high (total soluble sugars) and moderate (starch) light environments. The traits associated with total biomass were starch, stomatal conductance and transpiration for B. excelsa; leaf area ratio, leaf area root mass ratio, total soluble sugars and starch for C. alliodora; and RIA, leaf area ratio, and leaf area root mass ratio for S. macrophylla. The species obtained a high total biomass under mild to high irradiance but following different morphophysiological mechanisms. We discussed the potential to use these mechanisms in silvicultural systems designed to supply the plants with intermediate to high levels of light, for example enrichment planting in secondary forests or reforestation on degraded areas.

The early heading growth stage of rice plants in using the SRI method by giving liquid organic fertilizer of coconut husk and banana stems

Coconut husk and banana stem waste can be used as a source of organic material for plants which is utilized in the form of liquid organic fertilizer. This study aims to determine the interaction between types of liquid organic fertilizer and the concentration of liquid organic fertilizer. This research was carried out in Sungai Bangek, Balai Gadang Village, Koto Tangah District, Padang City from June until September 2022. The design used was a split plot in a randomized block design. The main plot is liquid organic fertilizer with 2 levels of coconut husk and banana stem while the subplot is liquid organic fertilizer concentration consisting of 7 levels (0, 50, 100, 150, 200, 250, 300 ml/liter). The data were analyzed through variance analysis using the F test and if significant, it was continued with Duncan New Multiple Range Test (DNMRT) with a significance level of 5%. The data is processed with Stat8 software. The observed variables consisted of plant height, the number of tillers, leaf area index, relative growth rate, and net assimilation rate. The results obtained on the growth variable have not shown significant results in every observed observation. There was a very strong correlation between the number of tillers and the leaf area index which had a unidirectional relationship. There was a fairly strong correlation between the leaf area index and net assimilation rate which has an opposite relationship.

Relationship of Improving Triticale Stored Seed Field Emergence by α-Amylase Enzyme on some Growth Characteristic and Biological Yield

A field experiment was carried out at the Research Station of the Field Crops Department - College of Agriculture - Tikrit University for the season 2021-2022. The experiment aimed to test the stimulating efficiency of stored triticale seed (Farah variety) by using water and alpha-amylase (α-amylase) enzyme. The experiment was carried out using a split plots arrangement, and the treatments were distributed according to a randomized complete block design in three replications. The main plots contained seed storage treatments for 6 months, 1.5, and 2.5 years, and the subplots treatments included seed stimulation treatments with distilled water, and concentrations of 1 and 2 mg L-1 in addition to the control treatment (dry seeds). The results showed a significant decrease in the percentage of emergence, crop growth rate (CGR), net assimilation rate (NAR), biological yield, and harvest index by increasing the storage period which did not affect the chlorophyll index in leaves significantly. Stimulation with the concentration of 1 mg L-1 recorded the best improvement in the characteristics of emergence percentage (88.77%), crop growth rate (0.02395 gm day-1), and harvest index (38.80 %). Stimulated seeds with a concentration of 2 mg L-1 gave the highest biological yield of 15.108 tons ha-1. However, it did not differ significantly from the stimulation treatment of 1 mg L-1. Stimulation factors did not affect the net assimilation rate and chlorophyll index. The interaction between factors was not significant according to the analysis of variance with the exception of the trait of biological yield, and the best interaction was between storage treatment for 6 months and concentration of 1 mg L-1 in most of the traits under study.

Impact of rice husk biochar date on the growth and production of edamame (Glycine max L. Merrill) in Ultisol

Edamame is one of the food crops that are in great demand by the public. Limited fertile land causes edamame cultivation to be expanded by using marginal land. Therefore, it is necessary to improve soil quality by using biochar rice husk biochar can be used as a soil enhancer which has a positive effect on soil properties. This study aims to obtain the best dose of biochar in edamame cultivation on Ultisol. This research was carried out from February to May 2022 in the field and in the Plant Physiology Laboratory, Faculty of Agriculture, Andalas University. This study consisted of 6 treatments with 4 replications arranged according to a Completely Randomized Design (CRD). The treatment was biochar, namely 0 tons/ha, 5 tons/ha, 10 tons/ha, 15 tons/ha, 20 tons/ha and 25 tons/ha. The data obtained from the observations were analyzed statistically with the F test at a 5% significance level. If it is significantly different, then further test is carried out Duncan’s New Multiple Range Test (DNMRT) further test at a 5% significance level. The results showed that the best dose of 20 tons/ha of rice husk biochar on relative growth rate, net assimilation rate and root crown ratio. but had no effect to plant height, the number of pods per plant and weight of 100 seeds.

Conservation crop establishment and foliar sulphur nutrition improve growth, photosynthetic efficiency and productivity of rainfed pearl millet

The study was undertaken to evaluate the effect of foliar sulphur (S) nutrition through Ammonium Thiosulphate (ATS) under conservation management on the growth, photosynthetic efficiency and productivity of rainfed pearl millet in dryland and rainfed ecologies of New Delhi in 2021 and 2022 crop years. The pearl millet established under conservation management (ZTCRret) achieved significantly higher crop growth rate (CGR) and relative growth rate (RGR) as a result of improved photosynthesis efficiency in terms of net assimilation rate (NAR) and a higher rate of productive tiller production (RPTP). The productivity of rainfed pearl millet under ZTCRret was improved by 26.6 and 13.5 % during 2021, and by 27.6 and 12.7 % over zero tillage (ZTCRrem) and conventional tillage (ConTil), respectively. The application of a recommended dose of S at 30 kg ha-1 resulted in a dramatic improvement in growth indices and photosynthetic efficiency over control and ATS doses upto 0.5% twice. Foliar application of ATS at 0.5% once and successively higher doses were found to improve the growth and productivity of pearl millet over S control, however, the dose of ATS at 1.0% twice could only achieve statistically similar levels of CGR and RGR to RDS that led to the higher RPTP with higher photosynthetic efficiency which resulted in non-significant yield difference. Therefore, the pearl millet established under zero tilled and crop residue retained plots supplemented with foliar feeding of ATS at 1.0% at 20 DAS (4-6 leaves stage) and 50 DAS (flowering stage) can be practiced under rainfed ecologies without significant yield loss.

Influence of Phosphorus and Zinc Application on Leaf Area Ratio (LAR) of Cowpea (Vigna unguiculata (L.) Walp) Varieties in the Scrub Savanna of Nigeria

Currently there is increasing attention to evaluate the possible Relative Growth Rate (RGR) of plant species, and to evaluate whether the disparities are principally caused by structural or by physiological characters. Leaf area ratio (LAR) of plant is defined as leaf area per unit total plant biomass and net assimilation rate. Phosphorus (P) and Zinc (Zn) are the most important factors affecting LAR of cowpea (Vigna unguiculata L. Walp). Two field trials were conducted at the Faculty of Agriculture and Agricultural Engineering Research Farm of Abubakar Tafawa Balewa University, Bauchi, North Eastern, Nigeria, between 2006 and 2007. The experiments consisted of fifty-four (54) treatments consisting of six varieties by three SSP levels by three Zinc levels. The objective of this study was to examine whether there are disparities in the LAR of cowpea varieties at different P and Zn levels or none? Bauchi is located at 100 22’, N latitude and 900 47’ E longitude at about 109.45m above sea level. Results indicated that year, varieties, P and Zn were found to have significant (P<0.05) effect on LAR. Kanannado recorded the highest LAR than other five varieties. The differences in LAR observed in the varieties may be attributed to the differences in phenotypes and climatic factors such as rainfall, sunshine and availability of nutrients. The increase in LAR indicated an encouraging influence on crop growth rate, dry matter and yield. Application of SSP at 50kgha-1 to Kanannado and IT89KD-288 was observed to be more valuable for enhancement of LAR and hence recommended for growers in the study area.

Effect of herbicides on plant growth and seed yield and quality of soybean (Glycine max L. Merr.)

Weeds create a great problem for soybean production and to overcome this problem a large number of weedicides are being applied prevalently worldwide. Gradually increasing the use of chemical herbicides, not only creating resistance against these chemicals among the weeds and polluting the environment, but also influencing the main crop and deteriorating the produce quality. To focus this problem a two-year experiment was laid down during ‘kharif’, at Norman E. Borlaug Crop Research Centre of G.B. Pant University of Agriculture and Technology, Pantnagar, Uttarakhand, to evaluate the detrimental effect of herbicides on soybean plant growth and seed quality. The study come up with the results that the growth parameters during 60-90 DAS (days after sowing) viz., crop growth rate (CGR 0.235 g/day), relative growth rate (RGR 0.014 g/ g/ day) and net assimilation rate (NAR 2.250 g/cm2/day) decreased due to higher weed competition in weedy plot. Weed competition also significantly reduced yield parameters like number of branches (3.8) and pod per plant (25.4), seed per pod (2.4), seed yield (386 kg/ ha), seed index (11.8 %), and straw yield (1611 kg/ha). The highest seed yield (2665 kg/ha) was recorded with application of diclosulam (as pre-emergence) followed by one hand weeding, which was statistically equal with the treatment in which diclosulam followed by haloxyfop (as post-emergence) was applied. These herbicides also significantly alter the fatty acid composition of soybean seed oil.

A natural variation in the promoter of GRA117 affects carbon assimilation in rice.

GRA117 is crucial in the process of carbon assimilation in rice as it regulates the development of chloroplasts, which in turn facilitates the Calvin-Benson cycle. Carbon assimilation is a critical process for plant growth, and despite numerous relevant studies, there are still unknown constraints. In this study, we isolated a rice mutant, gra117, which exhibited seedling albinism, delayed chloroplast development, decreased chlorophyll content, reduced yield, and seedling stress susceptibility, as compared to WT. Our further investigations revealed that gra117 had a significantly lower net photosynthetic carbon assimilation rate, as well as reduced levels of Rubisco enzyme activity, RUBP, PGA, carbohydrate, protein content, and dry matter accumulation. These findings provide evidence for decreased carbon assimilation in gra117. By mapping cloning, we discovered a 665bp insertion in the GRA117 promoter region that decreases GRA117 transcriptional activity and causes the gra117 phenotype. GRA117 encodes PfkB-type fructokinase-like 2, which is subcellularly localized in chloroplasts and is widely expressed in various rice tissues, particularly at high levels in leaf tissues. GRA117 transcription is regulated by the core region 1029bp before the start codon. Our quantitative RT-PCR and Western blot assays showed that GRA117 promotes the expression and translation of photosynthetic genes. RNA-Seq analysis revealed that GRA117 plays a significant role in photosynthetic carbon fixation, carbon metabolism, and chloroplast ribosome-related pathways. Our study supports that GRA117 promotes the Calvin-Benson cycle by regulating chloroplast development, ultimately leading to enhanced carbon assimilation in rice.

Variation in Leaf Pigment Complex Traits of Wetland Plants Is Related to Taxonomy and Life Forms

The leaf pigment complex traits of 44 wetland plant species from the Middle Urals (Russia) were studied to analyze their diversity in relation to taxonomy and life forms. The chlorophyll content per dry weight (ChlDW) and leaf area (ChlArea), the ratio of chlorophylls a and b, and CO2 uptake rates (ADW) were determined. ChlDW varied by 10-fold from 2.20 to 21.9 mg g−1 among the wetland plant species. The influence of taxonomy at the level of classes on the variation of the pigment complex traits was revealed. Dicots had greater ChlDW and had a greater proportion of chlorophylls in the light-harvesting complex (ChlLHC) than monocots. In dicots, ChlLHC was positively correlated with leaf area ratio (r = 0.63, p < 0.01), and the effect of life forms on the content and ratio of pigments was determined. In monocots, chlorophyll content was positively correlated with ADW (r = 0.75, p < 0.001) and plant height (r = 0.66, p < 0.001). In monocots, the effect of families on the pigment content was observed. The lack of differences in ChlArea between the different systematic groups and life forms indicates a similar ability of the leaf area unit to absorb a solar energy.

Assimilate Partitioning and Photosynthetic Parameters of Rice (Oryza sativa L.) in Response to Salicylic Acid Application

Salicylic acid (SA), a signaling molecule is known to affect various physiological processes like growth and development, photosynthesis, absorption and translocation of assimilates etc. Therefore, an experiment was conducted to study the effect of salicylic acid on assimilate partitioning and yield of rice. The experiment comprised of 14 treatments replicated thrice in Randomized Complete Block Design (RCBD). Foliar application of SA @ 50, 100, 150 & 200 µg ml-1 was done at boot leaf stage (BL), one week after boot leaf stage (1WABL) and at BL + 1WABL. Treatment of water spray and unsprayed (control) were also included. Findings reveal that application of 100 µg ml-1 SA at BL + 1WABL resulted in the highest grain yield, which was statistically similar to 150 µg ml-1 SA at BL + 1WABL. The higher productivity under respective treatments can be ascribed to higher crop growth rate, relative growth rate, net assimilation rate and improvement in partitioning of dry matter from vegetative parts to grains due to improved vascularization. Also there was improvement in photosynthetic efficiency in terms of total chlorophyll content; carotenoid content and Hill reaction activity under SA treated plots. Thus, the productivity enhancement in rice can be achieved through 2 foliar sprays of salicylic acid @ 100 µg ml-1 each at boot leaf stage + one week after boot leaf stage.

Potential of Kappaphycus alvarezii (seaweed) extract as biostimulant on the growth of mangrove propagules (Rhizophora mangle L.) through foliar application

This study investigated the potential of seaweed extract of Kappaphycus alvarezii as biostimulant in 3% concentration on the relative growth rate, net assimilation rate, and root to shoot ratio of mangrove propagules of Rhizophora mangle L. through different day- intervals of foliar application under field experiment. There were two factors included: factor A- types of treatment (A1- water, A2- seaweed extract, A3- commercial biostimulant); and, factor B- different day-interval of application (B1- 4 days, B2- 8 days, B3- 12 days). It was revealed that 3% concentration of seaweed extract of K. Alvarezii had no significant effect on the rate growth rate, net assimilation rate, and root to shoot ratio of mangrove propagules of R. Mangle L. Moreover, seaweed extract of K. alvarezii as biostimulant in 3% concentration had no significant difference to the commercial foliar biostimulant and to the different day- intervals of application. This study recommends to explore higher concentration of seaweed extract from K. Alvarezii on propagules of R. Mangle L. and other mangrove species in a greenhouse setting.

Assessing the effects of cultivar and nitrogen application rate on seedling vigor and early‐season canopy growth in cotton

AbstractCultivar variation in seed characteristics can affect seedling vigor, and nitrogen (N) availability influences early‐season growth in some instances. However, interactions between cultivar and N application rate for early‐season growth have received limited attention. Thus, the objectives of this research were to quantify the effects of cultivar, N‐application rate, and their interaction on early‐season growth, predict seedling vigor from plant morphology, and identify associations between early‐season crop growth rates (CGR) and other growth indices. To this end, a 2‐year (2018 and 2019) field study was conducted using six cotton cultivars having different seed characteristics and six different N‐application rates. In both years, all single‐plant and whole‐crop growth indices were affected by cultivar but not early‐season N‐application rates. A function was developed that was strongly predictive (R2 = 0.78) of seedling dry weight and utilized only plant height and mainstem node assessments. Leaf area index was a strong and consistent predictor of early‐season CGR, whereas net assimilation rate was only associated with CGR in one of the 2 years. Thus, it is concluded that of the two factors assessed in the current study, cultivar is the dominant driver of seedling vigor up to 35 days after planting. Additionally, leaf area development is a more consistent driver of early‐season CGR than average assimilation rates of the canopy. In contrast, an application of N at planting did not affect seedling vigor or early‐season canopy growth in cotton.

Análise da ação exógena de auxinas e citocininas na superação da restrição radicular em ficus Benjamin verde e variegado

Abstract Green and variegated Benjamin fig (Ficus benjamina) often suffer from root restriction when grown in pots. While exogenous cytokinin applications have proven effective in reversing this stress, the possibility that exogenous auxins, either alone or in combination with cytokinin, may also be helpful has received little attention. In this work, we analyse the response of green and variegated Ficus benjamina rooted cuttings growing in small pots to exogenous supply of auxin and cytokinin at different concentrations, either in single or combined applications. Our results show that both benzyl aminopurine (BAP) and indole acetic acid (IAA), at the highest concentration tested (100 mg L-1) increased leaf development and plant biomass accumulation in green and variegated Ficus genotypes. However, exogenous IAA and BAP appeared to elicit differential plant morpho-physiological responses. While BAP tended to enhance leaf appearance more than IAA did, the latter promoted leaf expansion in a steadier manner than BAP, thus resulting in plants with less, but larger, leaves than those treated with cytokinin. Despite these differences in plant architecture, regression analysis suggests that hormonal-induced growth promotion was solely attributable to enhanced carbon assimilation. Rather unexpectedly, IAA promoted net assimilation and photosynthesis rates at least as effectively as cytokinin. Possible mechanisms involved in growth and development promotion by exogenous application of both hormones are discussed. Auxin treatment may help overcome root restriction in Ficus as effectively as cytokinin in terms of growth promotion, although differences in plant architecture may arise as compared with plants sprayed with the latter hormone.