Root Sugar Content Research Articles

THE EFFECTS OF POTASSIUM APPLICATIONS ON DROUGHT STRESS IN SUGAR BEET: PART I. SUGAR BEET QUALITY COMPONENTS

This is the first in a series of papers describing the effects of potassium applications on drought stress in sugar beet. Drought stress is the stress to which there is the most exposure in agricultural areas. In this research, the effect of potassium applications under drought stress on some quality parameters of sugar beet, which is a strategic plant, was investigated. In the experiment, irrigation levels were kept at 33%, 66% and 100% of field capacity. Different doses (10-20-40-80 mg kg-1) of potassium were applied to the plants. The plants were grown in the growth chamber under controlled conditions (day/night 16/8 hours, 25/15 0C, 60-70% humidity). A comparison of the plants irrigated at the level of 100% of the field capacity and stressed plants showed that the root sugar content decreased by 53.18% and 65.1%, and shoot sugar content by 20.8% and 17.8% respectively at 66% and 33% irrigation levels. Root white sugar content (58.61 mg g-1) was obtained at the dose of 10 mg kg-1 potassium level, while the lowest (32.61 mg g-1) was obtained at the dose of 80 mg kg-1 potassium level. Shoot protein content has increased significantly with an increasing level of potassium under drought (33% and 66%) condition. The root α-amino nitrogen content decreased under drought stress with increasing potassium concentrations while it increased in non-stressed plants. According to the results obtained from the experiment, the potassium applied to the plants under drought stress led to the increase of the root sugar, root white sugar content and shoot protein content the reduction of root α-amino nitrogen content. Therefore, it can be said that potassium may play a critical role in reducing the negative effect of drought stress in sugar beet.

Effects of manganese on physiological characters of grapevine cultivars under salinity stress

Salinity is one of the most important environmental factors which have a significant effect on the growth and fertility. Manganese is an essential element that plays a key role as a nutrient in many plant metabolic processes. The present study was carried out to investigate the effects of manganese (1ppm) on Yaghoti and Ghara uzum - two cultivars of grapevine - which were planted and grown under salt stress (0, 50 and 100mmol L-1 NaCl) using greenhouse and hydroponics methods. Results on saline concentration showed led to a significant decrease in length, fresh and dry weight, photosynthesis pigments content, K+ and nitrate content, and K+/Na+ ratio of the plants. It also caused a significant increase in Na+ and Cl- ion concentration and soluble sugar content in shoots and roots of both cultivars. Ghara uzum was more sensitive than Yaghoti to salinity stress. Applying manganese to the medium, resulted in low level of salinity toxicity and sodium ion accumulation in the shoots for Ghara uzum cultivar. For Yaghoti, however, the application of manganese did not reduce the sodium ion accumulation in the shoots, but increased the salinity toxicity. Our findings suggest that Ghara uzum and Yaghoti cultivars had different responses to salinity, manganese and their interaction.

Negative effects of calcium on magnesium and potassium benefit for adaptability of Chinese prickly ash (Zanthoxylum bungeanum) grown on poor soils

The aim of this study was to provide information about how calcium (Ca), magnesium (Mg) and potassium (K) respond to changes in the sugar concentrations and carbon isotopic compositions (δ13C) of Chinese prickly ash under field condition, therefore, to show why negative effect of Ca on Mg and K would be beneficial for adaptability of Chinese prickly ash grown on poor soils. Chinese prickly ash samples were collected in the six areas with different mean annual precipitation. Drought stress was evaluated via carbon isotope signatures. Additionally, concentrations of Mg, Ca, K and sugar concentrations in foliage, roots and soils were analyzed. Increased soil available Ca concentrations did significantly inhibit foliar Mg partitioning, implying that Ca did negatively affect Mg partitioning. Changes of foliar Mg concentrations were strongly controlled by variations of balance between soil available Ca and Mg. Thus, an accurate assessment of plant nutrient status should be useful for precision nutrient management in the fields. Magnesium deficiency did significantly induce foliar sugar accumulation, therefore, there were negative relationships between Mg concentrations and δ13C values in foliage. In addition, increased sugar concentrations did significantly increase δ13C values, implying that drought or water stress induced the accumulation of sugar in foliage. Linear and power function regression analysis revealed that negative effects of Ca on Mg and K should be responsible for accumulation of soluble sugar in foliage, which may enhance a plant’s adaptability on poor soils.

Non-structural carbohydrate concentrations of Fagus sylvatica and Pinus sylvestris fine roots are linked to ectomycorrhizal enzymatic activity during spring reactivation

We evaluated whether changes in fine root non-structural carbohydrate reserves of Fagus sylvatica and Pinus sylvestris trees influence potential enzymatic activities of their ectomycorrhizal symbionts from winter towards spring reactivation, and whether these changes influence potential soil enzymatic activities. We analyzed sugar and starch concentrations in the fine roots of Fagus sylvatica and Pinus sylvestris and potential activities of ß-glucosidase, ß-xylosidase, and cellobiohydrolase (as proxies for carbon-degrading enzymes) as well as leucine aminopeptidase and chitinase (as proxies for nitrogen-degrading enzymes) of their dominant ectomycorrhizal symbionts as well as in the soil. Sugar concentrations in the fine roots were significantly positively correlated with enzymatic activities of the ectomycorrhizal symbionts. In Pinus sylvestris, both carbon- and nitrogen-degrading enzyme activities showed significant positive correlations with fine root sugar concentrations. In Fagus sylvatica, fine root sugar concentrations were explicitly positively correlated with the activity of nitrogen-degrading enzymes. The chitinase activity in the soil was found to be strongly positively correlated with the enzymatic activity of the ectomycorrhizal symbionts as well as with fine root sugar concentrations. Fine root carbohydrate concentrations of Fagus sylvatica and Pinus sylvestris trees and enzymatic activities of their associated ectomycorrhizal fungi are connected. The specific nutrient demand of the tree species during spring reactivation may affect ectomycorrhizal enzymatic activity via carbon mobilization in the fine roots of Fagus sylvatica and Pinus sylvestris. Moreover, our results suggest that trees indirectly contribute to the degradation of fungal necromass by stimulating ectomycorrhizal chitinase activity in the soil.

Impact of Irrigation and Fertigation on the Yield and Quality of Sugar Beet (Beta vulgaris L.) in a Moderate Climate

In Poland, under conditions of the moderate climate and transition between maritime and continental climates, the average rainfall totals of the growing season are in the range of 350–400 mm; however, they are distinguished by great temporal and spatial variability. Climatological studies demonstrate that the drought frequency is approximately 30%. Therefore, under such conditions, irrigation has a supplementary and intervention nature and is applied only when dry periods occur. The aim of this study was to determine the impact of sprinkler irrigation and increased nitrogen fertilization on the yield and quality of sugar beet roots and yield of sugar. The average increase of the yield under irrigation was 18.1 t·ha−1 which constituted a 22.8% increase in the yield. Furthermore, there was a marked tendency of a higher sugar content in the roots of irrigated plants. The absolute, relative, and unit average sugar beet root yield increases obtained under the influence of sprinkler irrigation and the lack of a significant diversity in the sugar content in roots confirm that irrigation contributed to an appropriate pace of plant growth and development. The increased rate of nitrogen fertilization (N2) of 160 kg N·ha−1 plus an additional 40 kg N·ha−1 resulted in the significantly greater root yields compared to the control (N1) (160 kg N·ha−1), i.e., an average of 7.6 t·ha−1 (9%). Based on the crop-water production function, the maximum root yields were obtained for the N1 rate at a total precipitation and irrigation amount of 382 mm, compared with 367 mm for the N2 rate.

Features of the formation of sugar beet hybrids productivity

Purpose. To reveal the features of the formation of sugar beet hybrids productivity depending on fertilizer options and harvesting time. Methods. Field, laboratory.Results. Biological differences in the growth and development and the mass of root crops formation allowed high yielding hybrids to respond to the use of supplemental mineral nutrition properly, and therefore, high productivity rates were also obtained on fertilized variants. When harvesting root crops in September, the ‘Romul’ hybrid in the control variant formed 54.0 t/ha of root crops, and with fertilizer N150P150K150 and N300P300K300 – 74.2 t/ha. The delay in harves­ting did not lead to a significant increase in the productivity of the investigated sugar beet hybrids. Thus, in the third decade of October, sugar beets on average formed 48.8–67.9 t/ha of root crops, and root crops had an average of 18.3–20.7% sugar. The best performance was provided by the hybrid ‘Sofiia’, so the control sugar content was 22.0%, and with the fertilizer N150P150K150 – 20.5% and N300P300K300 – 19.5%. The use of fertilizers N150P150K150 and N300P300K300 contributed to higher yields of root crops with lower sugar content, which corresponded to data obtained by other scientists.Conclusions. When harvesting in the third decade of September and being fertilized with N150P150K150, hybrids formed: ‘BTsChS 57’ – 66.8, ‘Heroi’ – 66.2, ‘Romul’ – 72.0, ‘Quarta’ – 66.0 t/ha of root crops, with fertilizer in a dose of N300P300K300 – 68.8; 68.1; 74.2 and 68.0 t/ha, respectively. It was proved that at the harvesting period in the third decade of October, ‘BTsChS 57’, ‘Heroi’, ‘Sofiia’ and ‘Romul’ were the best. In addition, the introduction of the mineral nut­rition in dose N300P300K300 did not provide a yield increase that could recoup additional mineral nutrition compared to the dose N150P150K150. In terms of sugar content of the sugar beet root crops, the hybrids ‘Heroi’ – 21.4%, ‘Sofiia’ – 21.8%, ‘Ukrainskyi ChS72’ – 21.3% and ‘Romul’ – 21.4% were the best at harvesting in the third decade of September; and in the third decade of October the maximum level of sugar content in root crops was in hybrids ‘Sofiia’ – 22.0% and ‘Umanskyi’ – 21.9%. The use of mineral fertilizers led to a decrease in the sugar content in roots by about 1.3–2.5% compared with unfertilized control options. Such a reaction of plants is caused by a sufficient level of soil supply with mineral nutrition compounds.

Effects of abscisic acid on soluble sugar content of Perilla frutescens seedlings under cadmium stress

The experiment aimed to study the effects of abscisic acid on soluble sugar content of Perilla frutescens seedlings under cadmium stress. The leaves of P. frutescens were foliage sprayed with different concentrations (0, 1, 5, 10, 20 μmol·L−1) of ABA under cadmium stress (10 mgkg−1). The results showed that the soluble sugar content in root, stem and shoot increased with the ABA concentration increasing at first, and then decreased. The soluble sugar content in leaf decreased with the ABA concentration increasing. The soluble sugar content in root and stem peaked when the ABA concentration was 5 pmol-L−1, which increased by 8.11% and 19.87% compared to the ABA concentration was 0 pmol-L−1, respectively. And the soluble sugar content in leaf peaked when the ABA concentration was 1 pmol-L−1, which increased by 1.04%. In conclusion, appropriate concentration of ABA could increase the soluble sugar content of P. frutescens under cadmium stress, and alleviated the stress of cadmium on P. frutescens seedlings to some extent.

Productivity of sugar beet sterility maintainers on selective agricultural backgrounds with regulated abiotic factors

Aim. To determine the variability productivity components of the sterility maintainers against the selective agricultural background; to differentiate the lines according to the environmental parameters of plasticity and stability; to select the best lines for obtaining highly adaptive heterotic hybrids. Methods. Breeding material testing against agricultural backgrounds with different combinations of controlled abiotic factors and the method of Eberhard-Russell. Results. The average yield increased by 0.4 t/ha on LGS+NNB and by 1.1 t/ha on LGS+RNB. LGS+RNB reduced sugar content in roots. The highest sugar content values were recorded in O-type 1 line on LGS+NNB (18.6%) and in the O-type 2 line on NGS+NNB (19.4%). O-type lines were differentiated according to the response to the change of abiotic factors. Conclusions. O-type lines are characterized by a specific response to the controlled abiotic factors. O-type 4 and O-type 6 lines can be attributed to intensive type. O-type 3 and O-type 5 lines are considered stable for both signs. O-type 1 and O-type 2 lines showed relative stability by yield and an intensive response to the variability of the medium by sugar content. Keywords: sterility maintainers, yield, sugar content, genotype effect, the coefficient of plasticity.

Effects of Abscisic Acid on Soluble Sugar Accumulation of Cyphomandra betacea Seedlings under Cadmium Stress

In this study, the effects of different concentrations (0, 1, 5, 10, and 20 μmol/L) of abscisic acid (ABA) on soluble sugar accumulation in Cyphomandra betacea seedlings under cadmium stress were studied. The results showed that spraying 10 and 20 μmol/L ABA could effectively increase the content of soluble sugar in roots, stems, leaves and aerial parts of C. betacea seedlings. Spraying 1 and 5 μmol/L ABA reduced the soluble sugar content in roots, stems, leaves and aerial parts of C. betacea seedlings. Therefore, the use of 20 μmol/L ABA can increase the accumulation of soluble sugar in C. betacea seedlings.

Effects of Living Pterocypsela laciniata and Its Straw on Soluble Sugar Content in Grape Seedlings under Selenium Stress

The pot experiment was conducted to study the effects of soluble sugar content of grape seedlings under selenium stress by intercropping and the application of straws in soil. There were five treatments: grape seedlings monoculture; intercropping with Pterocypsela laciniata and applying leaf, stem and root straws of P. laciniata in soil with grape seedlings, respectively. By analyzing, the results displayed that the soluble sugar content in root and stem was markedly lower than that in leaf and shoot. In five treatments, intercropping was significantly increased the soluble sugar content compared with the control. It promoted the growth and the nutrient substance of P. laciniata. On the contrary, applying root, stem and leaf straws of P. laciniata in soil reduced the soluble sugar content of grape seedlings. Obviously, applying P. laciniata straws could not improve the growth of P. laciniata. The content of soluble sugar was always ranked as: grape seedlings intercropping with P. laciniata seedlings > grape seedlings monoculture > applying the leaf straw of P. laciniata in soil with grape seedlings > applying the stem straw of P. laciniata in soil with grape seedlings > applying the root straw of P. laciniata in soil with grape seedlings. In a word, intercropping with P. laciniata seedling was a best treatment for improving the growth of grape seedlings compared to applying P. laciniata straws.

Changes of non-structural carbohydrates in Caryopteris mongolica seedlings during the process of drought-induced mortality

The changes and distribution of non-structural carbohydrate (NSC, including soluble sugar and starch) content in different organs of one-year-old Caryopteris mongolica seedlings were investigated under suitable water condition (CK), slow-dying drought stress, and fast-dying drought stress. There was no significant difference in soluble sugar content of all organs between slow-dying drought stress and CK. With the extended duration of drought, the soluble sugar content in stem increased firstly and then decreased, while starch and NSC contents decreased. The soluble sugar content in coarse roots decreased, while starch and NSC contents increased. The soluble sugar content in leaves increased, while starch and NSC contents of leaves decreased. The NSC content of leaves, stems, coarse roots and fine roots were 6.2%, 7.8%, 8.3% and 7.4% at the death time (80 days), respectively. Under fast-dying drought stress, soluble sugar content in all organs was higher than that in CK, while starch and NSC contents were lower than that in CK. With the increasing time, soluble sugar content of roots decreased, while starch and NSC contents increased. The soluble sugar, starch and NSC contents in stems increased. The soluble sugar content of leaves increased, while starch and NSC contents decreased. The NSC content of leaves, stems, coarse roots and fine roots were 5.9%, 6.6%, 8.9% and 7.7% at lethal time (30 days), respectively. Under different drought stress, non-structural carbohydrates among different organs of C. mongolica seedlings showed different dynamics. Under slow-dying drought stress, NSC gave priority to allocate energy for maintaining physiological metabolism of organs. Under fast-dying drought stress, NSC mainly maintained plant metabolism in the form of soluble sugar, regulated osmotic potential, promoted water absorption, and coped with drastic drought stress.

Effect of the Architecture of Fiber-Optic Probes Designed for Soluble Solid Content Prediction in Intact Sugar Beet Slices.

Sugar beet is the second biggest world contributor to sugar production and the only one grown in Europe. One of the main limitations for its competitiveness is the lack of effective tools for assessing sugar content in unprocessed sugar beet roots, especially in breeding programs. In this context, a dedicated near infrared (NIR) fiber-optic probe based approach is proposed. NIR technology is widely used for the estimation of sugar content in vegetable products, while optic fibers allow a wide choice of technical properties and configurations. The objective of this research was to study the best architecture through different technical choices for the estimation of sugar content in intact sugar beet roots. NIR spectral measurements were taken on unprocessed sugar beet samples using two types of geometries, single and multiple fiber-probes. Sugar content estimates were more accurate when using multiple fiber-probes (up to R2 = 0.93) due to a lesser disruption of light specular reflection. In turn, on this configuration, the best estimations were observed for the smallest distances between emitting and collecting fibers, reducing the proportion of multiply scattered light in the spectra. Error of prediction (RPD) values of 3.95, 3.27 and 3.09 were obtained for distances between emitting and collecting fibers of 0.6, 1.2 and 1.8 µm respectively. These high RPD values highlight the good predictions capacities of the multi-fiber probes. Finally, this study contributes to a better understanding of the effects of the technical properties of optical fiber-probes on the quality of spectral models. In addition, and beyond this specificity related to sugar beet, these findings could be extended to other turbid media for quantitative optical spectroscopy and eventually to validate considered fiber-optic probe design obtained in this experimental study.

Low Non-structural Carbon Accumulation in Spring Reduces Growth and Increases Mortality in Conifers Defoliated by Spruce Budworm

Spruce budworm (Choristoneura fumiferana) outbreaks are important disturbance events in the boreal forests of northeastern North America, causing major growth loss and widespread tree mortality. The physiological mechanisms leading to tree mortality remain poorly understood and two important functional traits, tree-ring width and concentration of stored carbohydrate, can serve as indicators of tree vitality during defoliation. This study aims to test the hypothesis that storage starch is an indicator of tree vitality by (1) exploring the link among reductions in storage, growth and mortality, and (2) identifying starch or sugar threshold to predict the risk of mortality. We use balsam fir and black spruce, two main host species of spruce budworm. We sampled 81 trees across seven experimental sites in eastern Quebec, Canada, and assessed defoliation intensity, tree-ring growth, and tree vitality. Soluble sugar and starch concentrations in needles, twigs, and roots were measured from spring to autumn. Under conditions of increased defoliation, carbon allocation to reserves and radial growth decreased in a similar manner for both species. Starch concentration within twigs and needles in May and June was the best indicator of carbon status in defoliated trees. We observed the highest reductions in growth two to three years prior to mortality concurrently with reductions in starch in May and June. When starch concentrations were lower than 28 mg·g-1dw in needles, the probability of balsam fir mortality exceeded 50%. At this level of starch, reserves and newly produced carbon are insufficient to support tree growth and vitality.

The Potassium Transporter SlHAK10 Is Involved in Mycorrhizal Potassium Uptake.

Most terrestrial plants form a root symbiosis with arbuscular mycorrhizal (AM) fungi, which receive fixed carbon from the plant and enhance the plant's uptake of mineral nutrients. AM symbiosis improves the phosphorous and nitrogen nutrition of host plants; however, little is known about the role of AM symbiosis in potassium (K+) nutrition. Here, we report that inoculation with the AM fungus Rhizophagus irregularis improved tomato (Solanum lycopersicum) plant growth and K+ acquisition and that K+ deficiency has a negative effect on root growth and AM colonization. Based on its homology to a Lotus japonicus AM-induced K+ transporter, we identified a mycorrhiza-specific tomato K+ transporter, SlHAK10 (Solanum lycopersicum High-affinity Potassium Transporter10), that was exclusively expressed in arbuscule-containing cells. SlHAK10 could restore a yeast K+ uptake-defective mutant in the low-affinity concentration range. Loss of function of SlHAK10 led to a significant decrease in mycorrhizal K+ uptake and AM colonization rate under low-K+ conditions but did not affect arbuscule development. Overexpressing SlHAK10 from the constitutive cauliflower mosaic virus 35S promoter or the AM-specific Solanum melongena Phosphate Transporter4 not only improved plant growth and K+ uptake but also increased AM colonization efficiency and soluble sugar content in roots supplied with low K+ Our results indicate that tomato plants have a SlHAK10-mediated mycorrhizal K+ uptake pathway and that improved plant K+ nutrition could increase carbohydrate accumulation in roots, which facilitates AM fungal colonization.

Effects of Chitosan on Soluble Sugar Content in Prunus davidiana Seedlings

A pot experiment was conducted to study the effects of different concentrations of chitosan solutions (0, 1, 2, 4, 6 g/L) on soluble sugar content in Prunus davidiana seedlings. The result showed that there was no significant difference of the soluble sugar content in roots, stems, leaves and shoot in P. davidiana seedlings between at 1 g/L concentration and the control. All concentration treatments were reduced the soluble sugar content in roots and stems of P. davidiana seedlings compared with the control. On the contrary, all concentration treatments were improved the soluble sugar content in leaves and shoot of P. davidiana seedlings compared with the control and the concentration treatment of 2 g/L and 4 g/L was at a higher level. All concentration treatments were improved the content in relative conductivity of blade in P. davidiana seedlings and the concentration treatment of 4 g/L was at a higher level. On the contrary, all concentration treatments were reduced the content in soil conductivity. Therefore, the chitosan solutions concentration of 2 g/L and 4 g/L concentration was beneficial to soluble sugar content in P. davidiana seedlings. On the contrary, high concentration of chitosan solutions was not good for soluble sugar content.

Effects of Biochar on Soluble Sugar Content in Peach Seedlings

A pot experiment was conducted to study the effects of different biochar types [addition of rape straw biochar (RB), addition of paddy straw biochar (PB), addition of wheat straw biochar (WB) and addition of corn straw biochar (MB)] on the soluble sugar content and plant height of peach seedlings. The result showed that the soluble sugar content in roots and leaves of peach seedlings treated with biochar was lower than the control. However, the soluble sugar content in stems was higher than control compared with the control. In the soluble sugar content in the aboveground part, there was no significant difference between the treatment of adding biochar and the control except for the treatment of PB. All the treatment of adding biochar increased the plant height of peach seedlings except the treatment of MB than the control and the treatment of RB and PB were at a higher level. Compared to control, all biochar addition treatments increased stem diameter of peach seedlings and the treatment of RB and PB were at a higher level. Therefore, the treatment of RB and PB was beneficial to the growth of peach seedlings.

The response of drought-tolerant sugar beet to salinity stress under field and controlled environmental conditions

Thirty-four sugar beet drought-tolerant half-sib families were screened in greenhouse experiment under saline (16 dSm−1) and normal conditions, and a subset of 10 tolerant genotypes were selected for evaluating of yield-related traits, Na+, K+, and α-amino-N nitrogen contents under saline field condition (12 dSm−1). Drought-tolerant genotypes showed a different tolerance level under salt stress. Significant correlation was observed between EP2s and STIEP2 in greenhouse with root yield (RY) in saline field condition. It should be possible that a simple measurement at 16 dSm−1 in the greenhouse can be used as main part of sugar beet salt-tolerant breeding program. In total, genotypes SBSI-DR I-HSF14-P.23 (# 16) and 436B-HSF9-P.27 (# 26) were recognized as salt- and drought-tolerant genotypes with low Na+ and K+ contents in root and high white sugar content (WSC) and RY in field. A larger panel of genotypes to validate this kind of association is necessary.

Supplementation of Nitrogen and its Influence on Free Sugars, Amino Acid and Protein Metabolism in Roots and Internodes of Wheat

Effect of different doses of nitrogen (N) (90, 120, 150 and 180 kg Nha–1) on the activities of aminotransferases and alkaline inorganic pyrophosphatase (AIP) in relation to the accumulation of proteins, amino acids and sugars in roots and internodes at 15 and 40 days post anthesis (DPA) stages was studied in six wheat genotypes namely HD 2967, GLU 1101, PBW 343, BW 9022, PH-132–4840 and PBW 550. Supra-optimal N doses (150 kg Nha–1 and 180 kg Nha–1) accentuated glutamate oxaloacetate transaminase (GOT), glutamate pyruvate transaminase (GPT) and alkaline inorganic pyrophosphatase activities in correspondence with an increase in amino acid, protein and sugar content in both roots and internodes in all the six genotypes. Activities of analyzed enzymes were significantly high at 15 days post anthesis (DPA) stage and thereafter declined at maturity (40 DPA) in parallel with decrease in amino acid contents. Maximum activity of GOT, GPT and AIP was observed in HD 2967 and GLU 1101 genotypes along with higher build up of proteins and amino acids which resulted in higher grain yield. Activity of GPT was comparatively high over GOT, indicating its major role towards protein synthesis. Grain filling processes in terms of proteins and amino acids were positively correlated with GOT and GPT activities while sugars were correlated to AIP. Thus, nitrogen acquisition and assimilation resulted in favoured utilization of N in form of amino acid and proteins accumulation while sugar content was also stimulated. Due to immense activities of aminotransferases and higher contents of amino acids and proteins in GLU 1101 and HD 2967 genotypes at optimal dose and higher dose of N, these genotypes hold future potential for developing new cultivars with better grain quality characteristics.

Physiological effects of cadmium stress on Astragalus membranaceus seedlings and alleviative effects of attapulgite clay on cadmium stress

In this study we investigate the effects of cadmium stress on Astragalus membranaceus seedlings and the alleviative effects of attapulgite clay in growth substrate on cadmium stress to A. membranaceus seedlings. The results showed that the Y (Ⅱ) (effective photochemical quantum yield of PSⅡ photosynthetic), qP(photochemical quenching coefficient), ETR(the rate of non-cyclic electrontransport through PSⅡ), and chlorophyll content of the leaves were significantly decreased with the increase of cadmium concentrations, while the cadmium content, non-photochemical quenching(NPQ, qN) of the leaves and cadmium content, MDA content, plasma membrane permeability, and the damage degree of root apical membrane of the roots were significantly increased. Simultaneously, the activities of APX(ascorbate peroxidase), SOD(superoxide dismutase), POD(peroxidase), CAT(catalase), soluble protein content, and soluble sugar content of roots were increased first but then decreased with the increasing cadmium concentration. Under the condition of without Cd stress, the attapulgite clay into the growth substrate did not significantly affect above physiological indexes of leaves, but significantly increased SOD activity and soluble sugar content of roots and decreased the MDA content, damage degree of root apical membrane of roots, while other physiological indexes did not significantly change. Under cadmium stress, the presence of attapulgite clay in the growth substrate significantly alleviated the cadmium-induced decreases Y (Ⅱ), qP, ETR and chlorophyll content of leaves, and the CAT activity, soluble protein content, and soluble sugar content of roots. Under condition with cadmium stress, the presence of attapulgite clay significantly alleviated the cadmium-induced increases of leaves cadmium content, qN and NPQ, and the cadmium content, MDA content, plasma membrane permeability, damage degree of root apical membrane, SOD, POD, and APX activity of the roots. And, the alleviative effects of attapulgite clay on cadmium stress to A. membranaceus roots were more obvious with the increase of cadmium stress time. The above results showed that the addition of attapulgite clay into the growth substrate has certain alleviative effect on the cadmium stress to A. membranaceus seedlings.

ANN1 and ANN2 Function in Post-Phloem Sugar Transport in Root Tips to Affect Primary Root Growth.

Annexins are a multigene family of calcium-dependent membrane-binding proteins that play important roles in plant cell signaling. Annexins are multifunctional proteins, and their function in plants is not comprehensively understood. Arabidopsis (Arabidopsis thaliana) annexins ANN1 and ANN2 are 64% identical in their primary structure, and both are highly expressed in seedlings. Here, we showed that ann-mutant seedlings grown in the absence of sugar show decreased primary root growth and altered columella cells in root caps; however, these mutant defects are rescued by Suc, Glc, or Fru. In seedlings grown without sugar, significant up-regulation of photosynthetic gene expression and chlorophyll accumulation was found in ann-mutant cotyledons compared to that in wild type, which indicates potential sugar starvation in the roots of ann-mutant seedlings. Unexpectedly, the overall sugar content of ann-mutant primary roots was significantly higher than that of wild-type roots when grown without sugar. To examine the diffusion of sugar along the entire root to the root tip, we examined the unloading pattern of carboxyfluorescein dye and found that post-phloem sugar transport was impaired in ann-mutant root tips compared to that in wild type. Increased levels of ROS and callose were detected in the root tips of ann-mutant seedlings grown without Suc, the latter of which would restrict plasmodesmal sugar transport to root tips. Our results indicate that ANN1 and ANN2 play an important role in post-phloem sugar transport to the root tip, which in turn indirectly influences photosynthetic rates in cotyledons. This study expands our understanding of the function of annexins in plants.