Plant Growth Index Research Articles

Correlation of the expression of metal tolerance protein genes with zinc accumulation and distribution in Malus halliana seedlings under zinc toxicity stress

The micronutrient zinc plays an essential role in the physiological and metabolic processes in plants; however, it becomes very toxic when present in elevated amounts. To evaluate the correlation of metal tolerance proteins (MTP) with Zn accumulation and distribution in Malus halliana seedlings under zinc toxicity stress, seedlings with 8 true leaves were exposed to different Zn concentrations (4, 25, 50, 100 μmol·L−1) in a hydroponic culture system. We found that excessive Zn stress leads to a decrease in plant growth indexes and the accumulation and distribution of Zn in Malus halliana. With increasing levels of Zn stress, the Zn concentration in roots was significantly higher than in stems and leaves. At 100 μmol·L−1 Zn, the Zn concentration in roots, stems and leaves increased by 45.88, 26.51 and 25.43-fold when compare to CK, respectively. The increase of bioaccumulation factor (BAF) and the decrease of translocation factor (TF) all indicated that Zn was accumulated in the roots. Correlation and hierarchical clustering analysis found that the expression of MTP genes is closely associated with Zn concentrations. The MTP2, MTP11 and MTPC2-like genes were significantly negatively correlated with Zn concentration in roots and were resistant to excessive Zn concentration and sequestration. The expression of MTP1 had organ-specificity that was significantly higher in stems and leaves than that in roots. The expression of MTPC4-like was significantly positively correlated with Zn concentration under the treatment of 4 μmol·L−1 Zn, but the correlation decreased under the high concentration of Zn stress, which indicated that the expression of MTP gene was affected by Zn concentration.

Effects of silicon nanoparticles on growth and physiology of wheat in cadmium contaminated soil under different soil moisture levels.

Soil degradation with different stress conditions like accumulation of cadmium (Cd) contents in soil and drought stress has become one of the most dangerous issues that obstruct the sustainable agriculture production. Silicon nanoparticles (Si NPs) play beneficial roles in combating various biotic and abiotic stresses but their role under combined metal and drought stress is not studied. A pot study was designed to determine the effect of Si NPs on wheat (Triticum aestivum L.) growth and uptake of Cd grown in Cd contaminated soil with different water levels under ambient conditions. Four different levels of Si NPs (0, 25, 50, and 100 mg/kg) were applied in the soil before 1 week of wheat sowing and two water levels (70% and 35% soil water-holding capacity) were introduced after 50 days of seed sowing for the remaining growth period. The lowest biomass, yield, and photosynthesis were observed in the control plants while oxidative stress and the highest Cd concentrations in shoots, roots, and grains were observed in the control plants, and the drought stress further enhanced this effect on the plants. The Si NPs treatments improved the plant growth indicators and photosynthesis, and reduced the Cd concentrations in wheat tissues, especially in grains either without or with drought stress. The Si NPs reduced the oxidative stress in leaves as was indicated by the reduced production of hydrogen peroxide, electrolyte leakage, and malondialdehyde contents, and increase in superoxide dismutase and peroxidase activities. The improvement in wheat growth and a reduction in oxidative stress and Cd concentration in tissues were dependent on the levels of Si NPs and the effect was the highest with the highest level of NPs used.

Fertilizer Source and Irrigation Depth Affect Nutrient Leaching During Coleus Container Production

Abstract Nutrient leaching during nursery container production can have negative effects on plant growth and the environment. The objective of this study was to evaluate effects of fertilizer source at two irrigation depths on nutrient leaching during coleus [Plectranthus scutellarioides (L.) Codd] ‘Solar Sunrise' container production to develop best management practices. Coleus received no fertilizer, a controlled-release fertilizer (CRF), or a water-soluble fertilizer (WSF) applied at 0.30 kg N and P per m3 (0.02 lb per ft3) and were irrigated at 1.9 or 3.8 cm.day−1 (0.7 or 1.5 in.day−1) for 56 days after planting (DAP). Leachate was analyzed every 7 DAP for inorganic N and dissolved total P (DTP). At 56 DAP, root biomass, leaf quality, and plant growth index were similar between CRF and WSF treatments at both irrigation depths. Highest inorganic N and DTP losses occurred within 21 DAP. Application of WSF resulted in higher cumulative N and DTP losses compared to CRF applications. Coleus irrigated at 3.8 cm.day−1 and fertilized with WSF resulted in higher DTP losses compared to CRF applications regardless of irrigation depth. Reducing irrigation reduced inorganic N leaching for each fertilizer source. Application of CRF provided consistent growth while curbing nutrient losses across both irrigation depths compared to WSF. Index words: controlled-release fertilizer, water-soluble fertilizer, nursery producers, best management practices. Chemicals used in this study: Micronutrients mix (Micromax®); controlled-release fertilizer (Osmocote® Classic); water-soluble fertilizer (Grower's Special). Species used in this study: Coleus [Plectranthus scutellarioides (L.) Codd] ‘Solar Sunrise'.

Controlled-release Fertilizers Improved Croton Growth and Reduced Nitrogen Leaching

Fertilizer management is an essential step in the production process, as it allows the plant to use its productive capacity to the fullest extent possible. Researchers have tested maximum nutrient use with reduced losses to the environment aiming to increase productivity with fewer environmental impacts. This study compared the effects of controlled-release fertilizers (CRFs) with water-soluble fertilizer (WSF) and clear water (control) on the growth and nutrient uptake of croton (Codiaeum variegatum L.) and nitrogen leaching. The experiment was conducted with three replications and six treatments: two rates (1.5 g and 3.0 g per liter of substrate) of two CRFs [Osmocote Plus (15% N, 3.93% P, and 9.96% K) and Basacote (15% N, 3.49% P, and 9.96% K)], WSF, and clean water as control. All CRFs were applied before planting and WSF was supplied as nutrient solution through automated moisture sensor activated irrigation system. Plant growth (number of leaves, leaf area, stem height, root volume, and shoot and root dry weights) and total nutrient contents in the leaf tissue were evaluated every 30 days. Electrical conductivity (EC), pH, nitrate, ammonium, and total nitrogen contents were measured in the leached solution. Indeed, results showed that CRFs at a low rate provided similar development and quality of croton plants compared with WSF. Plant growth indicators were similar until 90 days after transplanting (DAT). After that, at 150 DAT, the highest values to number of leaves and leaf area occurred with WSF and with the lowest CRF rate as compared with the other treatments and control. The highest root volume was found with the WSF, which resulted in larger roots compared with the other treatments. These results showed WSF can be replaced by CRFs at low rates on croton growth. Moreover, according to the visual scale, the best treatments were WSF and Basacote at the low rate, where plants were bright, with multicolored leaves with prominent orange shades. However, CRFs maintained pH and EC within the recommended range for the growth of croton and reduced the nitrogen leaching from the pots.

Effect of basic oxygen furnace slag on succession of the bacterial community and immobilization of various metal ions in acidic contaminated mine soil

As an immobilizing agent for metal ions, basic oxygen furnace slag may affect bacterial community succession, thus further promote metal ion immobilization in acidic contaminated soil. In this work, pot experiments were conducted to study the effects of adding 10 g/kg (S10) and 15 g/kg (S15) slag on soil properties, plant growth, bacterial community succession and various metal ion immobilization in acidic mine soils contaminated by Pb, Zn, Cu, Cr and Cd. The results showed that after 93 days of potting, the soil pH, electrical conductivity, total nitrogen and organic carbon content increased significantly (P < 0.05), and the dry weight of Poa pratensis L. increased significantly (P < 0.05) in S10 and S15 compared with in original soil group. With slag addition and plant growth, the diversity and richness indices of bacterial communities greatly improved, and at the genus level, the abundance of metal-tolerant bacteria and bacteria beneficial to plant growth increased, while the abundance of acidophiles decreased. After adding slag to the soil, the various metals were immobilized because slag could not only immobilize metal ions through ion exchange and coprecipitation, but also benefit plant growth and bacterial community succession which further promote the immobilization of metal ions.

A study of the treatment of high-salt chromium-containing wastewater by the photocatalysis-constructed wetland combination method.

In this study, iron ore slag as the photocatalyst was introduced into a constructed wetland simulation system. A comparative experiment of the constructed wetland method and photocatalysis-constructed wetland combination method that treats the high-salt chromium-containing wastewater was carried out. The best hydraulic retention time (HRT) of the photocatalysis-constructed wetland combination system was studied. The effects of these two methods on biochemical oxygen demand (BOD5), chemical oxygen demand (COD) removal and Cr(VI) reduction rate of the high-salt chromium-containing wastewater were analysed after 14 periods. The results showed that under the optimal HRT of 4 hours, the COD and BOD5 of the wastewater reduced by 47% and 31%, and the reduction rate of Cr(VI) was 83% separately in the constructed wetland system. The COD and BOD5 of the wastewater reduced by 83% and 42%, and the reduction rate of Cr(VI) was 96% separately in the photocatalysis-constructed wetland combination method system. At the same time, the changes in plant parameters under these two systems were studied, and the results showed that the addition of photocatalyst and hydrogen peroxide to constructed wetlands did not affect the normal indicators of plant growth. The results showed that the photocatalysis-constructed wetland combination method not only reduced the treatment time greatly, but also improved the quality of the treated wastewater significantly.

Combined of salicylic acid and Pseudomonas fluorescens CHA0 on the expression of PR1 gene and control of Meloidogyne javanica in tomato

Root-knot nematodes (Meloidogyne spp.) are among the most dangerous herbal parasites which destroy 8.8 to 14.6 percent of agricultural products annually. This study examined inducing resistance to tomato against Meloidogyne javanica, as well as time-dependent changes in the expression of PR1 gene, after applying salicylic acid (SA) and Pseudomonas fluorescens CHA0 (Pf) in the leaf tissue of healthy and infected tomatoes. Combined application of SA and Pf improved the plant growth and reduced root-galling, the number of eggs and egg-masses and reproduction factor. The results of the experiment of gene expression revealed that in all of the treatments, the expression of PR1 gene changed at different time points. The expression of PR1 gene in infected plants, 24 h after inoculation with nematode, was 98% higher than that of the control plants and 48 h after nematode inoculation, was about 58% less than that of control plants. The maximum expression of PR1 gene in nematode infected plants treated with Pf + SA was observed eight days after soil drench application of Pf that was 48 h after treatment with SA and 24 h after nematode inoculation and nine days after application of Pf, downregulation of the PR1 gene occurred. This study revealed that SA and Pf improved the plant growth indices and reduced the infection of Meloidogyne javanica in tomato plants and also it was observed that the expression of PR1 gene was significantly reduced in treatments with Pf and SA, as compared to their combination.

Justification of the method for phytoremediation of degraded and contaminated lands by composite vermicompost briquettes

The object of research is the effectiveness of the use of vermicompost products of vermicultivation in the practice of phytoremediation of degraded and technogenic contaminated lands. One of the problematic aspects in solving the scientific problem of reclamation of lands degraded as a result of technogenic activity is the long-term stage of biological restoration of the disturbed landscape. For a more efficient and quick reclamation, it is advisable to create a phytocenosis from tree-shrub vegetation, resistant to negative environmental influences. Well-tested biotechnologies of vermicultivation create the prerequisites for the use of waste products of the colonies of the worms of the genus Eisenia in the form of composite vermicompost briquettes for the needs of land phytoremediation, and it is proved in the study.The analysis of literary sources using modern technologies of vermicultivation and the use of vermicompost products for the needs of agriculture and land phytoremediation is carried out. The growth process of the biomass of worms of the Eisenia fetida species and the accumulation of vermicompost over time depending on the temperature of the medium are studied. The results of laboratory bioindication experiments with composite briquettes, consisting of vermicompost, loam and seeds of wild cereals, are presented. It is determined that the ratio of vermicompost and loam in the composition of composite briquettes, which is the most optimal for plant growth indicators, is 60:40 and 40:60 by mass, which makes it possible to justify the phytomeliorant working mixtures for biological land reclamation technologies.Laboratory studies have shown the promise of using vermicompost as a product of vermicultivation in the form of composite briquettes in the practice of phytoremediation of disturbed lands.

Chemical characterization and phytotoxicity assessment of peri-urban soils using seed germination and root elongation tests.

The peri-urban soil is exposed to pollutants because of its proximity to the city, which may influence the quality of agricultural products. In this study, the occurrence of 16 trace elements (TEs), 16 polycyclic aromatic hydrocarbons (PAHs), and 33 contaminants of emerging concern (CECs) was analyzed in two soil sites of the peri-urban area of Barcelona (Spain) (S2 and S3) and a pristine site (S1). Levels of Pb (S2 164 and S3 150 mg kg-1) are around 2.5 times higher than the guideline values. Values for Cu (178 mg kg-1) in S2 are 1.8-fold higher, whereas for Zn, levels are slightly above the threshold in S2 (208 mg kg-1) and S3 (217 mg kg-1). The total concentrations of PAHs are significantly below the limits: 24 ng g-1 dw (S1), 38 ng g-1 dw (S2), 49 ng g-1 dw (S3), whereas only some CECs are detected with low concentrations. We also developed a simple and rapid method to assess soil pollution. Here, we use two plant growth indexes (seed germination rate and root elongation at the initial stage) of three seeds (lettuce, tomato, and cauliflower) to assess soil chemical contamination on agriculture. In the peri-urban soil, the concentration of Pb was 2.5 times higher than the guideline values, whereas for Cu and Zn, values were slightly above their limits, while only few PAHs and CECs were detected. Results for principal component analysis suggest that root elongation is a more sensitive measurement endpoint than germination rate, especially for lettuce. The germination rate of tomato relied on the nitrate in the soil and decreased sharply in the site with pollution of Cu and As. Under the specific conditions of this study, cauliflower should not be recommended to assess environmental pollution due to its low sensitivity to pollutants. In conclusion, this is a low-cost, simple, and rapid method for evaluating the effects of chemical pollution of agriculture soils on seed growth.

Multi-walled carbon nanotubes improved growth, anatomy, physiology, secondary metabolism, and callus performance in Catharanthus roseus: an in vitro study.

This study was conducted to monitor the physiological and molecular responses of Catharanthus roseus (rose periwinkle) to multi-walled carbon nanotube (MWCNT) incorporation into the culture medium. The seeds were grown on hormone-free MS medium supplemented with 0, 50, 100, and 150 mgL-1of MWCNT. The supplementations of culture medium with MWCNTs led to significant increases in plant growth indexes such as leaf width, leaf area, leaf fresh weight, root length, and total plant biomass). Slight increases were also observed in chlorophyll a (Chla), Chlb, and carotenoid contents (mean = 18.6%) in MWCNT-treated seedlings. Protein concentrations increased by an average of 34% relative to the control. The application of MWCNT resulted in twofold increases in the catalase and peroxidase activities. A similar trend was also observed in the phenylalanine ammonia lyase activities (by an average of 36.5%), soluble phenols (by 23%), and alkaloids (by 1.7-fold). Moreover, upregulations (mean = 37-fold) in the transcriptions of the DAT gene resulted from the MWCNT supplementations. Exposure to MWCNT improved cell sizes and xylem conducting tissue in treated seedlings. The applications of MWCNTs also stimulated the callus initiation and performance, implying their effects on proliferation and possible differentiation. This study has provided evidence of role MWCNT play in improving plant performance and production of pharmaceutical secondary metabolites.

The effect of Rhizophagus irregularis on salt stress tolerance of Elaeagnus angustifolia roots

We assessed the effects of arbuscular mycorrhizal fungi (AMF) Rhizophagus irregularis inoculation on salt stress tolerance in roots of the drought-tolerant plant Elaeagnus angustifolia. We studied a plant growth index, spore density and hyphal length density of AMF, the Na+ contents and ultrastructure of root cells, as well as rhizosphere soil enzyme activities of mycorrhizal and non-mycorrhizal E. angustifolia seedlings under different salt stress. Under salt stress, growth of E. angustifolia with mycorrhizal inoculation was higher than that of non-inoculated treatments. The spore density and hyphal length density decreased significantly under salt stress in rhizosphere soil of mycorrhizal E. angustifolia seedlings (p < 0.05). The root cells of E. angustifolia seedlings inoculated with R. irregularis at 300 mmol L−1 salt had more organelles, greater integrity, and lower root Na+ contents than those of non-inoculated seedlings. In addition, the results showed notably higher activities of catalase, phosphatase, urease and saccharase in rhizosphere soil of the mycorrhizal seedlings in response to salinity compared to those of the non-mycorrhizal seedlings. Therefore, AMF inoculation could enhance salt stress tolerance in roots of E. angustifolia.

Water Conserving Irrigation Practices, Plant Growth, Seasonal Crop Coefficients, and Nutrition of Container-Grown Woody Ornamentals

Irrigation practices for container nursery crops often result in over-application and can lead to leaching of nutrients and reduced growth. Our objectives were to: (1) compare growth and foliar nutrient content for plants under daily water use (DWU) based irrigation treatments, (2) determine DWU of 14 woody ornamental taxa, and (3) classify taxa into irrigation functional groups based on crop coefficients (KC). Irrigation was applied daily to 8 taxa in 2009 and 2010 using a control of 19 mm and three irrigation treatments: (1) replacing 100% plant DWU (100DWU) each day, (2) alternating 100% DWU with 75% DWU in a 2-day cycle (100-75DWU), and (3) a 3-day cycle replacing 100% DWU the first day and 75% DWU on the second and third days (100-75-75DWU). In 2009, seasonal average DWU ranged between 8.8 and 17.3 mm depending on taxa and treatment. Most DWU-based treatments resulted in less water applied than the control, yet plant growth was not reduced, and for one taxon (Hydrangea paniculata ‘Limelight’) the 100DWU increased plant growth index. Lower foliar P and K concentrations were found for several taxa in control versus DWU treatments. In 2010, DWU for the season ranged between 2.1- and 22.0-mm d−1 depending on taxa and treatment. Growth was lower only for 100-75-75DWU Hydrangea paniculata ‘Limelight’ compared to other treatments and there were no differences in foliar nutrient content.

Leaf Tissue Nutrient Sufficiency Ranges of Four Heuchera Cultivars by Chronological Age

Coral bells (Heuchera sp.) are popular herbaceous perennials grown for their colorful foliage and venation and their aesthetic appeal in mixed containers and landscapes. Commercial coral bell production requires greenhouse or nursery growers to optimize production inputs such as managing mineral nutrition, thereby maximizing plant growth potential and foliage color. The objective of this study was to determine the optimum fertilizer concentrations, identify leaf tissue nutrient sufficiency ranges by chronological age, and to expand leaf tissue nutrient standards of coral bells grown in soilless substrates during container production. Coral bells (H. hybrida ‘Black Beauty’, ‘Cherry Cola’, ‘Marmalade’, and ‘Peppermint Spice’), varying in leaf color, were grown under one of six constant liquid fertilizer concentrations [50, 75, 100, 200, 300, or 400 mg·L−1 nitrogen (N)] with a constant level of water-soluble micronutrient blend in a greenhouse. Fertilizer concentrations for optimal plant growth and development were determined by analyzing plant height, diameter, growth index, and total dry mass, and were found to be 50 to 75 mg·L−1 N after a nine-week crop cycle. Recently mature leaf tissue samples were collected and analyzed for elemental content of 11 nutrients at 3, 6, and 9 weeks after transplant (WAT) from plants fertilized with 50 to 75 mg·L−1 N. The black- (‘Black Beauty’) and red- (‘Cherry Cola’) colored-leaved cultivars contained higher total N, phosphorus (P), potassium (K), calcium (Ca), sulfur (S), zinc (Zn), and boron (B) than the orange- (‘Marmalade’) and green- (‘Peppermint Spice’) colored-leaved cultivars. For instance, in mature growth, total N concentration for ‘Black Beauty’ and ‘Cherry Cola’ ranged between 3.45 to 3.63% and 3.92% to 4.18% N, respectively, whereas for ‘Marmalade’ and ‘Peppermint Spice’, ranges were between 2.98% to 3.25% and 2.78% to 3.23% N, respectively. Optimal leaf tissue concentration sufficiency ranges determined in this scientifically based study were narrower and often times higher than previously reported survey values for coral bells.

Satellite observed indicators of the maximum plant growth potential and their responses to drought over Tibetan Plateau (1982–2015)

The maximum plant growth potential in summer plays an important role in regulating annual carbon balance. However, indicators of plant growth at this stage are not well established. With high elevations on the Tibetan Plateau (TP), terrestrial ecosystems in this region are vulnerable to climate change and in particular, the frequently and intensified droughts as projected by ecosystem models. To better understand the maximum plant growth potential and its response to drought over the past three decades (1982–2015), we analyzed the impacts of drought, as indicated by the Standardized Precipitation-Evapotranspiration Index (SPEI), on two derived indicators of the maximum summer growth of plants, including the timing and the absolute value of the maximum Normalized Difference Vegetation Index (referred as the peak of growing season, POS and NDVImax, respectively). We found that both temporal and spatial patterns of SPEI, POS and NDVImax showed high spatial heterogeneity over TP. A higher SPEI led to a later POS for about 57% of regions but it reversed for the alpine sparse vegetation roughly account for 3.5% of all pixels, probably due to water availability of this plant functional type. For NDVImax, we found a significantly enhanced NDVImax in summer for a higher SPEI over ~70% of significant pixels, irrespective of differences among plant functional types. We further analyzed these correlations by temperature and precipitation gradients and found that an annual precipitation around 550 mm seemed to be a threshold separating the positive and negative impacts of drought on NDVImax. These results would be useful to better comprehend the impacts of drought on ecosystem response in a changing climate in future.

Phormidium Improves Seed Germination and Growth Parameters of Trifolium alexandrinum in Hexadecane-contaminated Soil

Petroleum is known as the main source of fuel and one of the most important environmental pollutants. Petroleum contaminated soil negatively influences plant growth and human health. Bioremediation of petroleum-contaminated soil could be achieved by adding cyanobacteria and photosynthetic microalgae in the soil. In the current study, the beneficial effects of cyanobacterium Phormidium sp. ISC108 treatment on seed germination and plant growth parameters were investigated on berseem clover plants exposed to 1% hexadecane- contaminated soil. For this purpose, after cultivation of berseem clover seeds in soil with 0 and 1% hexadecane, they were irrigated every two days by 3 ml Phormidium (OD600 = 0.7) and water for the cyanobacteria treatment and control, respectively. After 30 days, the biodegradability of hexadecane in the soil around the root was measured by gas chromatography mass-spectrometry (GC-MS). The results showed that Phormidium treatment accelerated germination of berseem clover seeds in both control and hexadecane- contaminated soil. Improvement of plant growth indices such as leaf area, plant fresh weight and leaf RWC due to cyanobacteria treatment was observed in hexadecane-contaminated soil. Hexadecane levels in the soil around the root of the plants irrigated by cyanobacteria were significantly decreased. In addition, the hexadecane degradation in the soil around the roots of berseem clover plant was increased in both control (water) treatment. In conclusion, due to positive effects of Phormidium treatment on seed germination, plant growth of berseem clover and hexadecane degradation, it can be effectively used to enhance plant capacity to cope with hexadecane toxicity in petroleum-contaminated soils.

Studies on Solanum torvum Swartz rootstock on cultivated eggplant under excess moisture stress

A field experiment on grafting two cultivars of brinjal, namely Surati Ravaiya Pink and Surati Ravaiya Purple onto the rootstock of Solanum torvum Swartz was conducted to elucidate the influence on plant survival and other horticultural parameters under excess moisture stress. The results revealed 24.59 and 17.18% higher plant survival in grafts of Surati Ravaiya Pink and Surati Ravaiya Purple over their respective counter parts. Plant growth indicators like plant height and stem diameter showed significant increase in grafts over normal plants. Grafted plants were quite early in flowering taking 38.60 and 34.53 days in Surati Ravaiya Pink and Surati Ravaiya Purple, respectively which corresponded significantly for earliness in picking by more than 5 days. Grafting also regulated heterostyly polymorphism positively and significantly in both the cultivars resulting in higher fruit set in grafted plants. Higher number of fruits per plant and enhanced cropping period were also important yield contributing traits achieved through grafting. The grafted plants showed tolerance to shoot and fruit borer exhibiting 22.79 and 17.86% infestation in Surati Ravaiya Pink and Surati Ravaiya Purple, respectively. Economic parameters analysis revealed higher net returns in grafted plants compared to non-grafted ones.

Regression Analysis to Estimate Morphology Parameters of Pepper Plant in a Controlled Greenhouse System

Regression analysis to predict growth indices of plant is essential for understanding the relationship between the total leaf area, production of fresh weight and dry matter, and expansion of the plant growth. An experiment was conducted to develop regression models for estimating leaf area, fresh weight, and dry weight from measurements of plant height at the vegetative phase of hot pepper (Capsicum annuum Linnaeus) grown in biodegradable pots in a greenhouse. Five models were evaluated and compared: linear regression model, two-order polynomial regression model (P. order 2), three-order polynomial regression model (P. order 3), four-order polynomial regression model (P. order 4), and power regression model. The models were compared using the coefficient of determination (R2), Pearson’s correlation coefficient (r), root mean square error (RMSE), relative standard error (RSE), and mean absolute percentage error (MAPE). Power regression involving plant height demonstrated the highest R-square among the other models with minimum error estimate for the expected leaf area (R2 > 0.96, r > 0.98, RMSE 0.98, r > 0.99, RMSE 0.97, r > 0.98, RMSE < 0.03, RSE < 0.02, and MAPE < 11.7) of the plant considering both the fit and degree of adjustment, and the interpretation of the model. This study creates scope for further experimentation on various species of crops by changing management practices under different environmental conditions to enhance knowledge and understanding of the growing patterns of plants.

Weed Suppression by Cover Plants in the Amazonian

The productivity of citrus plants has not reached its maximum potential due to the action of several factors that directly affect agricultural profitability. Among these factors, weed interference has a great importance since it causes a reduction in crop productivity. The aim of this study was to assess the effect of different cover crops on suppression of weeds in an orange orchard. The research was conducted in a commercial orange production area located in Rio Preto da Eva, AM, Brazil. The experimental design was a randomized block design with six treatments and four replications. Treatments were control, millet, jack bean, forage turnip, brachiaria, millet + jack bean. The evaluated characteristics were weed density, soil cover percentage, total weed dry matter, total cover plant dry matter and growth indices (leaf area index, leaf area ratio, and specific leaf area). Cover plants provided a good dry matter production and had a suppressive effect on weed growth, except for forage turnip. Brachiaria and jack bean presented the highest values of leaf area index and leaf area ratio.

Season Effects on Subsurface Constructed Wetlands Performance: Role of Radial Oxygen Loss of Phragmites australis

Radial oxygen loss (ROL) in plants plays an important role in the oxygen supply of subsurface‐flow constructed wetlands (SSF CWs). In this research, two types of microcosm, Phragmites australis‐planted wetlands (PA) and unplanted wetlands as the control (CT), are set up to investigate seasonal variations in ROL and their effects on pollutant removal. The chemical oxygen demand (COD) and NH4+‐N removal efficiency are detected, and the oxygen contributions produced by ROL are calculated for different seasons. The results show that the removal efficiency differences between PA and CT are significant in autumn and winter. The oxygen obtained from ROL is considerable in spring (120.12 ± 8.85% mg m−3 per day) and summer (1663.3 ± 36.4% mg m−3 per day), followed by autumn (494.32 ± 60.7% mg m−3 per day) and winter (27.95 ± 9.84% mg m−3 per day) and is positively correlated with the removal efficiency of COD (r = 0.786, p &lt; 0.01) and NH4+‐N (r = 0.758, p &lt; 0.01). Investigations of plant growth and physiological indexes showed that ROL is positively correlated with dry weight (DW), net photosynthetic rate (Pn), stomatal conductance (Gs), and especially root porosity (r = 0.731, p &lt; 0.01) and negatively correlated with plant height. These results indicate that the oxygen produced by ROL in CWs is considerable throughout the year, even in winter, and that root porosity has an important impact on seasonal variation in ROL.

Morphological and physiological response of Acer catalpifolium Rehd. Seedlings to water and light stresses

As a critically endangered species, Acer catalpifolium Rehd. is included in the wild plants with extremely small populations (WPESP) rescue and protection plan. Understanding of the responses of A. catalpifolium to various resource and environment conditions could help identify potentially suitable environments for its conservation. We used an orthogonal experiment design to evaluate the growth, morphological and physiological responses of A. catalpifolium and a widespread same-genus species A. mono to diverse water and light stresses. The results showed that a 75% soil water holding capacity and moderate shade are suitable for seedling growth. Drought and shade had significant negative effects on plant growth, biomass accumulation, and physiological functions. Lowering specific leaf areas (SLA), increasing root biomass allocation, and pigment content were the main strategies for enhancing water and light capturing abilities to acclimate to the limited ambient resources. The general plasticity index of plant growth, biomass, and physiological characteristics were higher in A. mono than in A. catalpifolium. We also explored the suitable light and water requirements for A. catalpifolium seedling growth. Our research would be useful for population regeneration and could aid in biodiversity conservation of Acer species.