Shoot Growth Rate Research Articles

Enhanced pollution removal from canal water by coupling aeration to floating treatment wetlands

Floating treatment wetlands (FTWs) are natural solutions for purifying polluted water, providing a green surface area and improving city landscape. This study investigated if the efficiency of FTWs can be improved by aeration for treating contaminated canal water. The three used plant species were Canna generalis, Phragmites australis, and Cyperus alternifolius. The experiment was carried out in three FTWs with aeration and three without aeration to compare the removal for COD, NH4 +-N, E. coli, PO4 3−-P, and Fe. In the aerated FTWs, air blowers were installed to run at two different air flow rates of 2.5 L min−1 (Batch 1) and 1.0 L min−1 (Batch 2). Aeration increased the dissolved oxygen concentrations in each tank, which came over 6.5 mg L−1 in both batches. This study sheds light on the positive impact of aeration has on COD and NH4 +-N removal: these are nearly three-fold higher compared to non-aeration conditions and reached approximately 99% (1.7-log reduction) for E. coli removal. Additionally, the plant growth rate in the aerated FTWs was higher than in the non-aerated ones. The average shoot growth rate of Phragmites australis was 0.76 cm d−1 for the aerated FTW which was two-fold higher compared to the non-aerated one.

Effects of Water and Nitrogen Regulation on Apple Tree Growth, Yield, Quality, and Their Water and Nitrogen Utilization Efficiency.

Apple tree productivity is influenced by the quantity of water and nutrients that are supplied during planting. To enhance resource utilization efficiency and optimize yields, a suitable strategy for supplying water and nitrogen must be established. A field experiment was conducted using a randomized block group design on five-year-old apple trees in Ningxia, with two irrigation lower limit levels (55%FC (W1) and 75%FC (W2)) and four N application levels (0 (N1), 120 (N2), 240 (N3), and 360 (N4) kg·ha-1). Our findings showed that leaf N content increased with a higher irrigation lower limit, but the difference was not statistically significant. However, the leaf N content significantly increased with increasing N application. The growth pattern of new shoots followed logistic curve characteristics, with the maximum new shoot growth rate and time of new shoot growth being delayed under high water and high nitrogen treatments. Apple yield and yield components (weight per fruit and number of fruits per plant) were enhanced under N application compared to no N application. The maximum apple yields were 19,405.3 kg·ha-1 (2022) and 29,607 kg·ha-1 (2023) at the N3 level. A parabolic relationship was observed between apple yield and N application level, with the optimal range of N application being 230-260 kg⸱ha-1. Apple quality indicators were not significantly affected by the irrigation lower limit but were significantly influenced by N application levels. The lower limit of irrigation did not have a significant impact on the quality indicators of the apples. Water and N utilization efficiencies improved with the W2 treatment at the same N application level. A negative relationship was observed between the amount of nitrogen applied and the biased productivity of nitrogen fertilizer. The utilization of nitrogen fertilizer was 127.6 kg·kg-1 (2022) and 200.3 kg·kg-1 (2023) in the W2N2 treatment. The apple yield was sustained, the quality of the fruit improved, and a substantial increase in water productivity was achieved with the W2N3 treatment. The findings of this study can be used as a reference for accurate field irrigation.

Seasonal coordination of aboveground vegetative and reproductive growth and storage in apple trees subjected to defoliation, flower and fruit thinning

Key messageThe growth rates of current-year shoots, fruits and trunks in apple trees peak sequentially during the growing season. The period of most intense growth coincided with the lowest NSC reserves.Vegetative and reproductive growth and storage are major carbon sinks in fruit trees; however, little is known about their mutual seasonal coordination. In this study, we monitored growth dynamics of trunks, fruits and current-year shoots together with the concentration of non-structural carbohydrates (NSC) in trees subjected to defoliation, early season flower thinning, mid-season fruit thinning and their respective combinations across the season. We found that defoliation had a negative effect on both trunk radial growth and annual fruit yield. Flower and fruit thinning caused lower fruit number per tree, but the individual fruits were larger resulting in a similar annual fruit yield among the treatments. Shoot extension growth was not significantly affected by the defoliation and flower and fruit thinning treatments. The concentration of non-structural carbohydrates was also similar across treatments. Modelled daily growth rates of shoots, fruits and trunks peaked sequentially one after another throughout the growing season with a delay of 15 and 18 days, respectively. The period of most intense growth of tree’s organs corresponded well with the lowest NSC reserves and a temporary depletion of starch in 1-year-old branches. Taken together, our study illustrates a tight temporal coordination of major carbon sinks and improves our understanding of sink/source relations of commercially important apple trees.

Species traits related to the invasion of woody plants in Patagonian deciduous forests.

The comparison of ecological, phenological, morphological and developmental traits between exotic invasive species and coexisting native species contributes to understand the driving mechanisms of successful invasions. This study aimed to examine which of these traits are related to the invasion of woody plants in the understory of deciduous North Patagonian forests of Argentina. We compared the phenology, shoot growth rate, number of leaves, biomass allocation, leaf herbivory, and recruitment type of two exotic deciduous trees, Crataegus monogyna and Sorbus aucuparia, with those of four coexisting native woody species (one deciduous, one semi-deciduous, and two evergreen species). Spring shoot growth took place several weeks earlier in both exotic species and in the deciduous native species than in the other native species; growth rates were higher in the exotics. Compared to coexisting native species, both exotic species developed shoots that were as long as or longer, had lower biomass allocation to leaves and higher allocation to roots, suffered lower leaf damage by herbivores and exhibited higher seed than vegetative recruitment. This study supports the idea that a combination of phenological, growth rate and mass allocation traits allow exotic species to preempt resources, thus favouring invasion processes.

Condicionamento de sementes com qualidade de luz e extrato de Cyperus rotundus L. modula a germinação e o crescimento inicial de plântulas de Moringa oleifera

Improving plant germination is essential to guarantee better quality seedlings. Thus, this research aimed to evaluate whether the seed priming with light quality (LIQ) and the aqueous extract of Cyperus rotundus (AEC) tuber could modulate the germination and initial growth of Moringa oleifera L. seedlings. The experimental design was a completely randomized in the 4x4 factorial scheme, composed of four LIQ conditions (white, blue, red, and distant red light) and four AEC concentrations (0, 25, 50 and 100%). Seed priming with red light reduced the average emergence time, while blue, red, and extreme red lights associated with 50% of aqueous extract of C. rotundus increased shoot initial length and photosynthetic pigment accumulation. Seed priming with blue light resulted in seedlings with a shorter final shoot length. However, application of 100% of aqueous extract of C. rotundus reversed this. The white light in combination with concentrations of 50 and 100% of AEC promoted a higher relative shoot growth rate of seedlings. The research revealed that seed priming with light quality and aqueous extracts of C. rotundus tubers modulates the germination and initial growth of M. oleifera seedlings. More work needs to be done to determine the responsible compounds in AEC that is responsible for priming growth as phytohormones.

Размножение in vitro перспективных сортов картофеля для возделывания в условиях Республики Коми

The paper deals with the results of clonal micropropagation of promising potato varieties for cultivation in the conditions of the Komi Republic. The study material is three potato varieties (Zyryanets, Pechorsky, Vychegodsky), characterized by the high resistance to late blight and abiotic stress factors in the conditions of the Komi Republic. The primary explants were weakly germinated eyeholes, as well as cuttings and shoot tips isolated from 14- and 30-day-old potato plants which underwent surface sterilization and then were cultivated in the Murashige–Skoog nutrient medium containing various hormones. The Pechorsky variety was identified to have the high growth index and specific growth rate of shoots in vitro. This variety can be included in studies on cell and genetic engineering aimed at creating potato forms with the complex resistance.

The effect of methyl jasmonate on growth, stevioside and rebaudioside A production in Stevia rebaudiana shoot culture using mist bioreactor

Steviol glycosides (SG) from Stevia rebaudiana have been used as natural sweeteners to substitute sucrose. SG production naturally needs large biomass. Therefore, it requires large area of cultivation. In vitro cultivation can be used as an alternative to propagate Stevia, as well as for increasing the production of SG. In this experiment, we conducted Stevia propagation in bioreactor and induced SG production through methyl jasmonate (MeJa) elicitation. The objective of this study was to evaluate the effect of MeJA on plant growth and SG contents in Stevia shoot cultivated using mist bioreactor. Elicitation was carried out by MeJa spraying for 30 min every 6 h. In treatment A, we used 10 μM MeJa for 72 h and 100 μM MeJa for 24 h for treatment B. The results showed that treatment A gave higher increase in shoot growth (485%), biomass production (547%), and relative growth rate (0.13) compared to treatment B. There was no significant difference in stevioside content among treatments (A and B) and controls, meanwhile treatment B produced rebaudioside A (0.0113 mg/g) higher than treatment A (0.0062 mg/g). We concluded that treatment A was better in inducing growth and treatment B could be used to increase rebaudioside A.

Shoot Growth and Virus Elimination by Antiviral Agents in Node Cultures of Three Rose Cultivars

Background and objective: This study was carried out to examine the effects of antiviral agents on shoot growth and virus elimination during node culture in rose 'Deep Purple', 'Natal Briar' and 'Pink Beauty' infected with TRSV and ArMV.Methods: Three varieties of roses confirmed to be infected with TRSV and ArMV through ImmunoStrip® Tests were node-cultured, and the medium was treated with antiviral agents ribavirin and vidarabine at 0, 10, 20, and 40 mg⋅L<sup>-1</sup> . After 60 days of culture, shoot growth and virus infection rates were evaluated.Results: In 'Deep Purple', vidarabine treatment inhibited shoot growth and survival rate more than ribavirin, and had no effect on virus elimination. Treatment of 20 mg⋅L<sup>-1</sup> ribavirin was no significant difference in shoot growth and survival rate compared to control, and TRSV and ArMV infection rates were lowered to 25% and 0%, respectively. In 'Natal Briar', treatment of 10-20 mg⋅L<sup>-1</sup> ribavirin showed no statistical difference in shoot growth compared to the control, but the infection rates of TRSV and ArMV were 100%. The shoot growth and survival rate were greatly suppressed in treatment of 10 mg⋅L<sup>-1</sup> vidarabine, but both TRSV and ArMV infection rates were 50%. In 'Pink Beauty', the higher the treatment concentration of ribavirin and vidarabine, the more the shoot growth was suppressed. Ribavirin had no effect on TRSV elimination, and 20 mg⋅L<sup>-1</sup> vidarabine treatment showed that both TRSV and ArMV infection rates were 50%.Conclusion: Depending on the type and concentration of the antiviral agent, the elimination effects of viruses were different for each variety of rose. It was most effective to treat 20 mg⋅L<sup>-1</sup> ribavirin in 'Deep Purple', 10 mg⋅L<sup>-1</sup> vidarabine in 'Natal Briar', and 20 mg⋅L<sup>-1</sup> vidarabine in 'Pink Beauty' in media for TRSV and ArMV elimination.

Effect of Mowing on Wheat Growth at Seeding Stage.

Winter wheat is used as forage at the tillering stage in many countries; however, the regrowth pattern of wheat after mowing remains unclear. In this study, the growth patterns of wheat were revealed through cytological and physiological assessments as well as transcriptome sequencing. The results of agronomic traits and paraffin sections showed that the shoot growth rate increased, but root growth was inhibited after mowing. The submicroscopic structure revealed a decrease in heterochromatin in the tillering node cell and a change in mitochondrial shape in the tillering node and secondary root. Analysis of the transcriptome showed the number of differentially expressed genes (DEGs) involved in biological processes, cellular components, and molecular functions; 2492 upregulated DEGs and 1534 downregulated DEGs were identified. The results of the experimental study showed that mowing induced expression of DEGs in the phenylpropanoid biosynthesis pathway and increased the activity of PAL and 4CL. The upregulated DEGs in the starch and sucrose metabolism pathways and related enzyme activity alterations indicated that the sugar degradation rate increased. The DEGs in the nitrogen metabolism pathway biosynthesis of the amino acids, phenylpropanoid biosynthesis metabolism, and in the TCA pathway also changed after mowing. Hormone content and related gene expression was also altered in the tillering and secondary roots after mowing. When jasmonic acid and ethylene were used to treat the wheat after mowing, the regeneration rate increased, whereas abscisic acid inhibited regrowth. This study revealed the wheat growth patterns after mowing, which could lead to a better understanding of the development of dual-purpose wheat.

Chilling Requirements to Relieve Bud Dormancy in Black-fruited Aronia Taxonomic Groups Is Related to Ploidy and Geographic Origin

The genus Aronia Medik., also known as chokeberry, is a group of deciduous shrubs in the Rosaceae family, subtribe Malinae. The two commonly accepted black-fruited Aronia species are black chokeberry [Aronia melanocarpa (Michx.) Elliott] and aroniaberry [Aronia mitschurinii (A.K. Skvortsov & Maitul)]. The geographic range of wild A. melanocarpa is the Great Lakes region and the northeastern United States, with a southerly extension into the higher elevations of the Appalachian Mountains. Wild A. melanocarpa found in New England are diploids, whereas plants throughout the rest of the range are tetraploids. A. mitschurinii is a cultivated hybrid between ×Sorbaronia fallax (C.K.Schneid.) C.K.Schneid. and A. melanocarpa and exists as a tetraploid. There is currently limited diversity of Aronia genotypes in the ornamental and fruit industries, and many of the current cultivars are not adapted to the southern United States and similar environs with limited chilling to break winter dormancy. The goal of this study was to determine 1) the chilling requirements for A. mitschurinii ‘Viking’ and 2) the range of chilling requirements for wild A. melanocarpa genotypes from different geographic origins. Two experiments were conducted in which plants were subjected to various chilling accumulation treatments and then moved to a greenhouse for observation of budbreak and subsequent growth. Expt. 1 was conducted at the University of Maryland at Wye, MD, and focused solely on the commercial cultivar A. mitschurinii ‘Viking’. Outdoor, ambient fall and winter temperatures were used to achieve the chilling treatments. In Expt. 1, we determined the optimal chilling requirements for A. mitschurinii ‘Viking’ to be greater than 900 h using the single temperature model. Expt. 2 was conducted at the University of Connecticut and focused on wild genotypes, plus A. mitschurinii ‘Viking’. A fixed temperature cold room was used to achieve chilling treatments. In Expt. 2, we found A. melanocarpa genotypes from southern regions in the United States required chilling accumulation of 600 h (single temperature model), compared with genotypes from northern regions that required more than 900 h of chilling accumulation. Tetraploid A. melanocarpa required 900 h of chilling to break bud, but diploid A. melanocarpa required 1200 h of chilling to break bud. Expt. 2 confirmed the 900-h chilling requirement for A. mitschurinii ‘Viking’. For both experiments, the rate of budbreak and shoot growth was positively correlated with increasing amounts of chilling.

Haplotype-Based Genome-Wide Association Analysis Using Exome Capture Assay and Digital Phenotyping Identifies Genetic Loci Underlying Salt Tolerance Mechanisms in Wheat.

Soil salinity can impose substantial stress on plant growth and cause significant yield losses. Crop varieties tolerant to salinity stress are needed to sustain yields in saline soils. This requires effective genotyping and phenotyping of germplasm pools to identify novel genes and QTL conferring salt tolerance that can be utilised in crop breeding schemes. We investigated a globally diverse collection of 580 wheat accessions for their growth response to salinity using automated digital phenotyping performed under controlled environmental conditions. The results show that digitally collected plant traits, including digital shoot growth rate and digital senescence rate, can be used as proxy traits for selecting salinity-tolerant accessions. A haplotype-based genome-wide association study was conducted using 58,502 linkage disequilibrium-based haplotype blocks derived from 883,300 genome-wide SNPs and identified 95 QTL for salinity tolerance component traits, of which 54 were novel and 41 overlapped with previously reported QTL. Gene ontology analysis identified a suite of candidate genes for salinity tolerance, some of which are already known to play a role in stress tolerance in other plant species. This study identified wheat accessions that utilise different tolerance mechanisms and which can be used in future studies to investigate the genetic and genic basis of salinity tolerance. Our results suggest salinity tolerance has not arisen from or been bred into accessions from specific regions or groups. Rather, they suggest salinity tolerance is widespread, with small-effect genetic variants contributing to different levels of tolerance in diverse, locally adapted germplasm.

Enhanced selectivity and recovery of phosphate and nitrate ions onto coffee ground waste biochars via co-precipitation of Mg/Al layered double hydroxides: A potential slow-release fertilizer

In this study, the feasibility of Mg/Al layered double hydroxides (LDH) functionalized coffee ground waste biochars (LDHMgAl@CWGB) as a potential adsorbent to selectively recover phosphate (PO43−) and nitrate (NO3−) ions in aqueous phases and their consecutive uses as a slow-release fertilizer for stimulating the plant growth were identified. The higher adsorption capacity of PO43− and NO3− ions by LDHMgAl@CWGB (PO43− = 6.98 mgP/g, NO3− = 2.82 mgN/g) compared with pristine coffee ground waste biochars (CWGB; PO43− = 0.19 mgP/g, NO3− = 0.32 mgN/g) was mainly due to the incorporation of Mg/Al mixed oxides and Cl contents. Chemisorption and intra-particle mainly controlled the adsorptive recovery of PO43− and NO3− ions by CWGB and LDHMgAl@CWGB in aqueous phases and their adsorption toward CWGB and LDHMgAl@CWGB proceeded endothermically and spontaneously. The changes in the major adsorption mechanisms of PO43− and NO3− ions from ligand exchange (CWGB) to electrostatic surface complexation and anion-exchange (LDHMgAl@CWGB) supported the conclusion that the alternation of the surface features through Mg/Al LDH functionalization might improve selectivity and adsorption capacity of PO43− and NO3− ions onto CWGB under the co-existence of Cl−, SO42−, and HCO3− ions. Since PO43-- and NO3−-loaded LDHMgAl@CWGB exhibited much higher seed germination, root and shoot growth rates of garden cress seeds (Lepidium sativum L) than other liquid and solid matrices, including 5 mgP/L PO43− and 5 mgN/L NO3−, 10 mgP/L PO43− and 10 mgN/L NO3−, and LDHMgAl@CWGB, it can be postulated that PO43-- and NO3−-loaded LDHMgAl@CWGB could be practically applicable to the agricultural field as a slow-release fertilizer to facilitate the seed germination, root and shoot growth of the plants.

Seasonal dynamics of shoots growth in <i>Forsythia ovata</i> Nakai plants: Rhythmicity of apical and radial growth

The aim of the study was to establish the type (linear or non-linear) and shape (presence of extremes and trends) of the time dependences of apical and radial growth rates for shoots of two types (branching and formation) in woody plants. The object of the study was an introduced in the Middle Urals ornamental early-flowering shrub species Forsythia ovata Nakai. Seasonal dynamics of morphometric parameters of two types of shoots, which differ in intensity of growth and origin (developing from the apical or dormant buds of the skeletal branch respectively), was examined. Also, there was made an assessment of their relationship with air temperature and precipitation values. Apical and radial growth are accompanied by oscillations of increments. The duration of individual phases of oscillations is about 7 or more days, which makes it possible to attribute this phenomenon to infradian growth rhythms. The weak relationship between the characteristics of the observed oscillations and weather conditions indicates the predominantly endogenous nature of the observed morphogenetic processes. The growth of formation shoots begins 4 weeks later than branching shoots. This delay is apparently related to the time necessary for activation of dormant bud growth. Seasonal dynamics curves of rates and accelerations of the apical and radial shoot’s growth have the shape of previously unobserved oscillations with phases fading in amplitude and changing in duration. The growth ends 1–2 months before the environmental conditions become unfavorable. The oscillations of the growth rate of shoots are apparently associated with the action of two or more differently directed factors, which determine the increase in volume of different segments of the shoot. These factors include the different contribution of cell division and elongation to the change in the geometric dimensions of the apical meristem domains. The main differences in the seasonal dynamics of the apical and radial increments for both types of shoots are: the duration of growth (6–8 and 4 weeks, respectively), the number of extremes, the amplitude and the duration of individual phases of oscillations. Higher amplitudes of the growth rate oscillations in shoots formation compared with branching shoots, cause bigger values of the formation shoots total increments. The dynamic curves of the apical growth rates have two maxima, while those of the radial growth have only one. Each type of growth, despite the delay in the onset of the formation shoots, has the same total duration. The shapes of curves of seasonal changes in speeds and accelerations of shoot growth values are also similar for different types of shoots. These similarities indicate that shoots have the same “programs” of growth regulation, ultimately determined by the genotype. The rhythmic growth of both types of shoots during the season suggests the existence of the relationship in time between the rates of division and growth of cells located in functionally different groups of cells in the apical meristem zone.

Ant13 Encodes Regulatory Factor WD40 Controlling Anthocyanin and Proanthocyanidin Synthesis in Barley (Hordeum vulgare L.)

Flavonoid compounds like anthocyanins and proanthocyanidins are important plant secondary metabolites having wide biological activities for humans. In this study, the molecular function of the Ant13 locus, which is one of the key loci governing flavonoid synthesis in barley, was determined. It was found that Ant13 encodes a WD40-type regulatory protein, which is required for transcriptional activation of a set of structural genes encoding enzymes of flavonoid biosynthesis at the leaf sheath base (colored by anthocyanins) and in grains (which accumulate proanthocyanidins). Besides its role in flavonoid biosynthesis, pleiotropic effects of this gene in plant growth were revealed. The mutants deficient in the Ant13 locus showed similar germination rates but a decreased rate of root and shoot growth and yield-related parameters in comparison to the parental cultivars. This is the seventh Ant locus (among 30) for which molecular functions in flavonoid biosynthesis regulation have been determined.

Effect of shading imposed by the algae Chaeotomorpha linum loads on structure, morphology and physiology of the seagrass Cymodocea nodosa

In shallow coastal waters, seagrass and macroalgae occur together but under eutrophic conditions, bloom-forming algae can take over seagrasses causing an irreversible regime shift. Understanding the effect of macroalgae loads on seagrass meadows at an early stage can help prevent the loss of these ecosystems and the services they provide. In the present study, in situ experiments were conducted for 90 days in Bekalta (eastern coast of Tunisia) to assess the response of the seagrass Cymodocea nodosa when challenged with shading induced by filamentous macroalgae Chaetomorpha linum. Structural, morphological and physiological variables were regularly measured during the experiment. Shaded plants showed a sharp decline in shoot density, growth rate, and above-ground biomass, the impact being more pronounced on the physiological traits. Besides, shading by C. linum induced a significant increase in the contents of leaf photosynthetic pigments and phenolic compounds, whereas causing a decrease in soluble protein and sugar concentrations. Thus, shading imposed by C. linum loads appeared to induce a phoadpatative response in C. nodosa concomitant with carbon mobilization.

Characterization of the Difference between Day and Night Temperatures on the Growth, Photosynthesis, and Metabolite Accumulation of Tea Seedlings

Currently, the effects of the differences between day and night temperatures (DIFs) on tea plant are poorly understood. In order to investigate the influence of DIFs on the growth, photosynthesis, and metabolite accumulation of tea plants, the plants were cultivated under 5 °C (25/20 °C, light/dark), 10 °C (25/15 °C, light/dark), and 15 °C (25/10 °C, light/dark). The results showed that the growth rate of the new shoots decreased with an increase in the DIFs. There was a downward trend in the photosynthesis among the treatments, as evidenced by the lowest net photosynthetic rate and total chlorophyll at a DIF of 15 °C. In addition, the DIFs significantly affected the primary and secondary metabolites. In particular, the 10 °C DIF treatment contained the lowest levels of soluble sugars, tea polyphenols, and catechins but was abundant in caffeine and amino acids, along with high expression levels of theanine synthetase (TS3) and glutamate synthase (GOGAT). Furthermore, the transcriptome data revealed that the differentially expressed genes were enriched in valine, leucine, and isoleucine degradation, flavone/flavonol biosyntheses, flavonoid biosynthesis, etc. Therefore, we concluded that a DIF of 10 °C was suitable for the protected cultivation of tea plants in terms of the growth and the quality of a favorable flavor of tea, which provided a scientific basis for the protected cultivation of tea seedlings.

Potassium Efficiency of Different Crops Grown on a Sandy Soil under Controlled Conditions

The objective of this work was to study K efficiency ofdifferent crops and determine the plant parameters affecting it. The studywas carried out using 14 different crops and cultivars grown on a sandysoil rich in humus, with two potassium fertilisation levels undercontrolled conditions. The studied crops showed different K efficiencyreflected in different dry matter yield production in unfertilised relative tofertilised treatments. All crops had, at low K supply, less than optimum Kconcentration in dry matter, indicating that the soil K concentration didnot meet the K requirement of the plants. Thus, the ability to produce highdry matter yield indicated superior adaptability to K deficiency. Theefficiency mechanisms employed by the different crops were low shootgrowth rate and/or high root length - shoot weight ratio and a high uptakerate per unit root, i.e. the influx, or low internal K requirement. Cropswith high influx had higher calculated concentration gradients, since theycaused further decrease of the concentration at the root surface. As such,they were able to create steeper concentration gradients between bulk soilsolution and root surface. This resulted in higher diffusive flux to theroots.

Potassium Efficiency of Wheat and Sugar Beet Evaluated Under Field Conditions

This study was conducted to investigate the potassium (K)efficiency of wheat and sugar beet under field conditions and to identifythe varying mechanisms or factors behind their efficiency. Data wereobtained from a long term fertilizer experiment, on a K "fixing" sandyclay loam in Bavaria, southern Germany, in which K fertilization ratesvaried from 0 to 1000 kg K ha-1 year-1 with the last K application in 1986.In 2003, sugar beet and spring wheat were sown on March 13 th and April4 th , respectively. At 4 and 5 harvests for wheat and sugar beet,respectively, random samples of shoots, roots and soil of each speciesfrom the unfertilized (-K) and the highest fertilizer level of 1000 kg K ha-1(+K) treatments were analyzed. Sugar beet and wheat had similar Kefficiency producing 76 % and 80 % beet and grain yield on unfertilizedcompared with fertilized treatments, respectively. As compared to wheat,sugar beet had a higher internal K requirement, two times higher shootgrowth rate (GRs), 34% to 48 % of the wheat root length (RL), andconsequently a larger GR/RL, that is higher demand for K uptake on theroots. However, sugar beet showed an exceptionally high uptakeefficiency of the single roots or influx, which was 5 times higher inunfertilized treatments, as compared with wheat. Wheat K efficiency wasattributed to a higher utilization efficiency or lower internal requirement,slow growing shoots and a large root system. Further investigations arenecessary to study the mechanism by which sugar beet was able toachieve a higher influx than wheat.

Experimental thermocline deepening highlights the resilience of the seagrass Posidonia oceanica: An opportunity to investigate shoot adaptability

The deepening of the thermocline, correlated to the rising temperature, can contribute affecting seagrass performance in a changing climate scenario. Here, the effect of the thermocline deepening on the seagrass Posidonia oceanica has been investigated in Cyprus through a manipulative experiment that allowed also testing the effects of the irradiance, origin depth and translocation. P. oceanica shoots were collected from 31 m of depth and transplanted at 12 m under a shading net, simulating the 31 m light conditions. Morphology (i.e. leaf area, leaf necrosis, number of leaves) and physiology (i.e. growth rate) were evaluated. Thermocline and origin depth effects were found with an increase of leaf necrosis, while a translocation effect was highlighted by a decrease in leaf area. No differences in shoot growth rate due to treatments were found. This experiment indicated an overall wide morphological and physiological acclimation of P. oceanica cuttings in coping with future thermocline conditions and it indirectly provides information for restoration efforts.

Allelopathy of Ricinus communis and light spectrum variation decrease emergence and growth of Cyperus rotundus

Weeds negatively influence agricultural production. However, those losses depend on weed specie, its time of emergence, and period of interference on agricultural crops. Synthetic herbicides are commonly used to control these plants species; however, they may cause damage to the environment, human beings and animals health, and this problem justify the need to develop alternative bioherbicides. To evaluate the allelopathic potential of Ricinus communis (Castor bean) and light spectrum variation on the emergence and growth of Cyperus rotundus L., a trial was carried out in a protected environment with 15% of brightness reduction at the Center for Agricultural and Environmental Sciences at the Paraíba State University. Four aqueous extract concentrations of R. communis leaves were tested (0, 5, 10, and 15%) and four light spectrums variations (white, purple, blue, and red lights). Variables such as emergence, length, dry matter accumulation and growth rates of shoots and root of C. rotundus seedlings were assessed. Data were analyzed by normality test, analysis of variance, polynomial regression, and averages test. Soot and root emergence, length, and dry matter accumulation of C. rotundus seedlings were reduced due to the allelopathy caused by R. communis aqueous extract leaves (15% concentration) and under purple or red light spectrum radiation.