Milk-ripe Stage Research Articles

Biological Control of Ustilaginoidea virens Using Chelerythrine Suspension

Background High efficiency, low toxicity, and environmentally safe pesticides are increasingly being sought and developed to ensure sustainable development and high-yield agricultural production. Chelerythrine has strong inhibitory effects against the mycelial growth of crop pathogens such as Fusarium oxysporum, Anthrax, and grey mold. Our previous studies have shown that chelerythrine inhibits fungus spore germination by up to 86.7% and induces the apoptosis of Ustilaginoidea virens cells. The application of chelerythrine as a green biological pesticide would not only enhance agricultural production but also enhance ecological protection. Materials and Methods The formulation of a chelerythrine suspension concentrate was selected. According to the ratio of experimental design requirements to preparation sample, six groups were set up in the field assay; the first spraying was performed approximately 7 days before the rice rupture period, and the second spraying was performed after 10 days. The control effect was investigated at the milk-ripe stage. The present study preliminarily investigates the safety of chelerythrine as a pesticide using the oral acute toxicity test for mice. Results In the present study, the effect of chelerythrine as the main ingredient in suspension concentrate formulations and its field effect on rice false smut (RFS) was investigated. The pesticide in the suspending agent was sprayed twice and had superior effects with regard to the prevention and control of RFS in the field. The control effect was 95.88% at an application rate of 192 mL/ha, with low residue, environmentally safe, and low resistance characteristics. An acute toxicity test following intragastric administration in mice showed that the LD50 of chelerythrine suspension was 1580 mg·kg−1, which was much lower than those of other low-toxicity commercial pesticides. Conclusion Chelerythrine suspension was a low-toxicity agent and exhibited the characteristics of an environmentally friendly plant pesticide. The application of chelerythrine suspension could facilitate the achievement of the goal of pesticide reduction efficiency.

Unequal carbon and nitrogen translocation between ramets affects sexual reproductive performance of the clonal grass Leymus chinensis under nitrogen addition

Sexual reproduction is crucial for population continuity in clonal plants. The effect of nutrient translocation between ramets on sexual reproduction of clonal plants under nitrogen addition remains unclear. In this study, we focused on clonal fragments of Leymus chinensis reproductive ramets with different number of vegetative ramets connected to tillering nodes. A series of pot experiments was conducted under nitrogen addition, including 13C and 15N bidirectional labelling of vegetative ramets and reproductive ramets at the milk-ripe stage, determination of the 13C and 15N amount translocated, and assessment of the quantitative characteristics, nitrogen and carbon concentrations of reproductive ramets and vegetative ramets. Nitrogen addition promoted the translocation of 13C while inhibiting 15N between vegetative ramets and reproductive ramets. With an increase in the number of connected vegetative ramets, the 13C translocated by reproductive ramets and the 15N translocated by reproductive and vegetative ramets gradually increased. The translocation of 13C and 15N between vegetative and reproductive ramets was bidirectional and unequal. The translocated amount of 13C and 15N from reproductive ramets to vegetative ramets was always higher than that from vegetative ramets to reproductive ramets. Nitrogen addition did not prominently affect the sexual reproductive performance of L. chinensis, whereas the number of connected vegetative ramets both positively and negatively affected sexual reproductive performance. Ramet biomass is an important driver of nutrient acquisition by L. chinensis ramets. We demonstrate for the first time that unequal nutrient translocation between ramets affects sexual reproductive performance in L. chinensis. The findings contribute to an enhanced understanding of the reproductive strategies of clonal plant populations in future environments.

Starch molecular structures in relation to properties of ratoon rice produced by different ratooning practices

The development of forage-grain ratoon rice (RR) pattern could ensure food security and promote silage production. Herein three indica rice varieties were used to investigate the influence of different forage clipping stages (heading, milk-ripe, wax-ripe, and full-ripe) on starch molecular structures and RR properties. The apparent amylose contents (AAC) of starches increased, but pasting viscosities, gelatinization temperatures and starch sizes decreased with the postponement of clipping stages due to the retardation of endosperm development. The starches showed A-type crystalline structure with increased in vitro digestibility; however relative crystallinity decreased by 13.45 % to 23.89 %. The short fa (DP 6–12) chains of amylopectin increased while long fb3 (DP ≥ 37) chains decreased (p < 0.05). The proportions of amylose chains with DP 100–2000 increased but those with DP 2000–20,000 decreased. Rice grain strength was positively correlated with fb3 chains while negatively correlated with fa chain. The hardness of cooked RR was positively correlated with AAC while negatively correlated with fb2 (DP 25–36). RR clipping at milk-ripe stage had the highest grain strength and moderate texture properties. The elucidation of structure-property relationships is helpful for RR utilization and development of suitable cultivation conditions for RR production.

Clonal dominant grass Leymus chinensis benefits more from physiological integration in sexual reproduction than its main companions in a meadow.

The bioecological characteristics of plants determine their status and role in the community. The advantages of dominant species in the community compared with companion species in terms of physiological and ecological characteristics remain unclear. When both dominant and companion species in grassland plant communities are clonal, these plants are able to share resources within clones (physiological integration). However, it is unclear how the clonal dominant and companion species differ in the effect of their physiological integration on sexual reproduction. We chose Leymus chinensis, the dominant species of the most widespread meadow plant communities in the semiarid and arid regions of northern China, and its main companion species L. secalinus, Calamagrostis ripidula, C. pseudophragmites, and C. epigeios and conducted a series of in situ field experiments in a homogeneous environment, including the determination of the phenotypic characteristics of reproductive ramets with connected (allowing physiological integration) and disconnected (preventing integration) tillering nodes for each species, as well as 15N leaf labeling of ramet pairs at the milk-ripe stage. In the clonal populations of the five grasses, physiological integration between vegetative ramets and reproductive ramets interconnected by tillering nodes significantly increased the leaf, stem, inflorescence and ramet biomasses of reproductive ramets, and relative changes in ramet biomass were greatest in L. chinensis. 15N labeling showed that vegetative ramets supplied nutrients to reproductive ramets through tillering nodes; the amount of translocated 15N per unit of reproductive ramet biomass was highest in L. chinensis. Overall, our results indicate that in the five clonal grasses, physiological integration between functionally different ramets under tillering node connections had a significant positive effect on sexual reproduction, indicating interspecific consistency in the contribution of physiological integration to sexual reproduction between the dominant and companion species, but this positive effect was greater in the dominant species L. chinensis than in the four main companion species. Therefore, differences in the physiological integration ability between the dominant and main companion species, identified for the first time in this study, may explain, at least partly, the dominance of L. chinensis in the community.

Влияние основных приемов и способов возделывания ярового ячменя на площадь ассимиляционной поверхности и индекс листовой поверхности посевов в почвенно-климатических условиях Курской области

Purpose: to determine the influence of the cultivar, seeding rate and application of mineral fertilizers when cultivating spring barley on the assimilation surface area of one plant and the leaf surface index of crops according to the crop growth phases in the soil and climatic conditions of Kursk region. Materials and methods. The studies were conducted in 2022 and 2023 in the field experience at Federal Agricultural Kursk Research Center in grain-fallow crop rotation. The experimental scheme includes the study of three cultivars – Suzdalets, Prometheus, Despina. The second factor is seeding rates: 3, 4, 5, 6 million units of viable seeds per 1 ha. The third factor is the levels of mineral fertilization: control without fertilizers and N₃₀P₃₀K₃₀. Results. It was found that the assimilation surface area of one spring barley plant in the seedling stage depended to a greater extent on the cultivar (by 40 %), and it also increased under the influence of mineral fertilization (by 16 %). The leaf area index of spring barley in the seedling stage depended by 89 % on the seeding rate. During the tillering stage, the leaf area depended by 72 % on the year conditions. Research during the crop blooming stage revealed that the main factor influencing the assimilation surface area and leaf area index was the year of study (31 and 44 %, respectively), the cultivar factor provided 23 and 27 % of the indicator variation, respectively, and the mineral fertilization – 20 and 30 %, respectively. During the milk-ripe stage, due to the leaves dying off, a decrease in the photosynthetic parameters of spring barley is observed. Conclusion. It has been determined that the assimilation surface area of one plant and the leaf area index are very dynamic indicators and largely depend on the year of research, the cultivar and the mineral fertilization. During the initial period of crop growth, the leaf area index is affected by the seed application rate.

Screening of Salt-Tolerant Thinopyrum ponticum Under Two Coastal Region Salinity Stress Levels.

To accelerate the exploitation and use of marginal soils and develop salt-tolerant forage germplasm suitable for the coastal regions of China, seven lines of decaploid tall wheatgrass [Thinopyrum ponticum (Podp.) Barkworth and D. R. Dewey, 2n = 10x = 70] were transplanted under low (.3%) and high (.5%) salt conditions for a comprehensive analysis at the adult-plant stage. Differences were observed among these materials, especially in terms of grass yield, agronomic characteristics, and physiological and biochemical indices. Line C2 grew best with the highest shoot total fresh and dry weights under all conditions except for the milk-ripe stage in Dongying in 2019. The total membership value of C2 also reflected its excellent performance after transplanting. As superior germplasm, its relatively high antioxidant enzyme activities and chlorophyll a/b ratio suggested C2 may maintain normal metabolic and physiological functions under saline conditions. Furthermore, decaploid tall wheatgrass as a forage grass species has a high nutritive value beneficial for animal husbandry. Accordingly, line C2 may be used as excellent germplasm to develop salt-tolerant cultivars in the Circum-Bohai sea.

Evaluation of the Tolerance Ability of Wheat Genotypes to Drought Stress: Dissection through Culm-Reserves Contribution and Grain Filling Physiology

Drought stress is one of the limiting factors for grain filling and yield in wheat. The grain filling and determinants of individual grain weight depend on current assimilation and extent of remobilization of culm reserves to grains. A pot experiment was conducted with eight wheat cultivars at the Pot House to study the grain filling and the contributions of reserves in culm, including the sheath to grain yield under drought stress. Drought stress was enforced by restricting irrigation during the grain-filling period. The plants (tillers) were harvested at anthesis, milk-ripe, and maturity. The changes in dry weights of leaves, culm with sheath, spikes, and grains; and the contribution of culm reserves to grain yield were determined. Results revealed that drought stress considerably decreased the grain filling duration by 15–24% and grain yield by 11–34%. Further, drought-induced early leaf senescence and reduced total dry matter production indicate the minimum contribution of current assimilation to grain yield. The stress reduced the contribution of culm reserves, the water-soluble carbohydrates (WSCs), to the grains. The accumulation of culm WSCs reached peak at milk ripe stage in control, varied from 28.6 to 84 mg culm−1 and that significantly reduced in the range from 14.9 to 40.6 mg culm−1 in stressed plants. The residual culm WSCs in control and stressed plants varied from 1.23 to 8.12 and 1.00 to 3.40 mg g−1 culm dry mass, respectively. BARI Gom 24 exhibited a higher contribution of culm WSCs to grain yield under drought, while the lowest contribution was found in Kanchan. Considering culm reserves WSCs and their remobilization along with other studied traits, BARI Gom 24 showed greater drought tolerance and revealed potential to grow under water deficit conditions in comparison to other cultivars.

Genotypic variation of wheat (Triticum aestivum L.) in grain filling and contribution of culm reserves to yield

To study the genotypic variation in the rate of grain filling and contribution of culm reserves to yield in wheat, an experiment was conducted consisting 12 popular cultivars of Bangladesh, viz., BARI Gom21 (Shatabdi), BARI Gom22 (Shufi), BARI Gom23 (Bijoy), BARI Gom24 (Prodip), BARI Gom25, BARI Gom26, Akbar (BAW 43), BARI Gom18 (Protiva), BARI Gom19 (Sourav), BARI Gom20 (Gourab), Agrani (BAW38), and Kanchan (BAW28). Tillers were sampled from anthesis to maturity to determine the changes in dry weights of different parts to examine the contribution of culm reserves to grain yield. The results in the experiment revealed that the grain yield varied from 2.61 to 5.35 ton/ha with the mean of 4.18 ton/ha. Among the cultivars BARI Gom24, BARI Gom26, BARI Gom19, and BARI Gom23 appeared as high yielders while Kanchan, Agrani, BARI Gom20, BARI Gom22 as the low yielders. Generally, high yielding cultivars showed higher total dry mass accumulation compared to low yielding ones. Moreover, high yielding cultivars also showed higher water soluble carbohydrates (WSCs) contents in culm at milk ripe stage than the low yielders. In general, contribution of culm WSCs to grain yield was more in high yielders than low yielders and it ranged from 2 to 29% of total grain weight. So, higher contribution of culm reserves resulted in higher grain yield of wheat.

Influence of Seasonal Dynamics on Carbohydrate, Lipid, and Protein Contents in Phaseolus vulgaris Pods

The carbohydrate, lipid, and protein contents of Phaseolus vulgaris L. pods during the milk-ripe and fruit-ripening stages were studied and their compositions and physicochemical parameters were established. The content of water-soluble polysaccharides decreased while that of pectinic substances increased during fruit ripening. The monosaccharide composition of the polysaccharides included acidic and neutral monosaccharides in various ratios. The compositions of neutral lipids (NL), their fatty acids (FAs), glycolipids (GLs), and protein amino acids were established. The NL were two times less; GL, 1.5 times less during fruit ripening than during the milk-ripe stages in P. vulgaris pods. The fatty acids of the two stages were dominated by saturated components, predominantly 16:0 acid. The nonessential amino acids in both stages were dominated by aspartic and glutamic acids; essential, isoleucine and leucine.

Identifying key regulatory genes of maize root growth and development by RNA sequencing

Root system architecture (RSA), the spatio-temporal configuration of roots, plays vital roles in maize (Zea mays L.) development and productivity. We sequenced the maize root transcriptome of four key growth and development stages: the 6th leaf stage, the 12th leaf stage, the tasseling stage and the milk-ripe stage. Differentially expressed genes (DEGs) were detected. 81 DEGs involved in plant hormone signal transduction pathway and 26 transcription factor (TF) genes were screened. These DEGs and TFs were predicted to be potential candidate genes during maize root growth and development. Several of these genes are homologous to well-known genes regulating root architecture or development in Arabidopsis or rice, such as, Zm00001d005892 (AtERF109), Zm00001d027925 (AtERF73/HRE1), Zm00001d047017 (AtMYC2, OsMYC2), Zm00001d039245 (AtWRKY6). Identification of these key genes will provide a further understanding of the molecular mechanisms responsible for maize root growth and development, it will be beneficial to increase maize production and improve stress resistance by altering RSA traits in modern breeding.

Development of a Rapid Approach for Detecting Sharp Eyespot Resistance in Seedling-Stage Wheat and Its Application in Chinese Wheat Cultivars.

Sharp eyespot, caused by Rhizoctonia cerealis, has become one of the most severe diseases affecting global wheat production in recent decades. Quick and efficient screening methods are required to accelerate the development of cultivars for sharp eyespot resistance in wheat breeding. Here, a two-step colonized wheat kernels (TSCWK) method for the inoculation and classification of sharp eyespot resistance in seedlings was established in a greenhouse. After preliminary verification of the reliability of the method in two replicates, 196 wheat cultivars were assessed for sharp eyespot resistance, and significant correlations were identified among the four replicates (r = 0.78 to 0.84; P < 0.01). Furthermore, the 196 cultivars were scored for sharp eyespot resistance at the milk-ripe stage using traditional toothpick inoculation in the field. Correlation and linear regression analysis showed that the application of this approach at the seedling stage showed good consistency with the traditional field method. Moreover, the scoring of 442 cultivars using the TSCWK method indicated that most cultivars from the Huanghuai valley were susceptible to R. cerealis, suggesting an urgent need to improve sharp eyespot resistance in this region. Additionally, the relative resistance index of sharp eyespot decreased in the surveyed cultivars of the region with time. This study offers a rapid and effective approach for the identification of wheat sharp eyespot resistance and provides valuable germplasm for improving sharp eyespot resistance in wheat breeding.

Phenotypic Plasticity in Sexual Reproduction Based on Nutrients Supplied From Vegetative Ramets in a Leymus chinensis Population.

Phenotypic plasticity is considered a major mechanism that allows plants to adapt to heterogeneous environments. The physiological integration between the interconnected rhizomes or stolons of clonal plants influences the plasticity of such plants in heterogeneous environments. However, the determinants of plasticity of reproductive ramets in clonal plants in homogeneous environments are unclear. Here, we chose Leymus chinensis, a perennial rhizomatous grass, and conducted a series of field experiments in situ, including grading sampling of reproductive ramets and different connection forms of vegetative ramets labeled with 15N at four reproductive stages. Reproductive ramet biomass, inflorescence biomass, seed number, seed-setting percentage, reproductive allocation, and reallocation significantly increased with an increase in the number of vegetative ramets connected to tillering nodes, and the plasticity indexes of these six phenotypic characteristics showed similar increasing trends. The amount of nutrients supplied from the connected vegetative ramets to the reproductive ramets was significantly affected by the transfer direction, reproductive stage, and position order of the vegetative ramets. Throughout the sexual reproduction stage, nutrients were preferentially transferred to the acropetal reproductive ramet in L. chinensis populations. The amount of nutrients supplied from the connected vegetative ramets to the reproductive ramets at the milk-ripe stage, when sexual reproduction was most vigorous, was significantly larger than that at other reproductive stages. The amount of nutrients supplied from the spacer vegetative ramet to the acropetal reproductive ramet was significantly larger than that to the basipetal reproductive ramet. The closer the vegetative ramet was to the reproductive ramet, the more nutrients were supplied; the amount of nutrients supplied was significantly negatively related to the position order of the vegetative ramet. We identified the determinant of plasticity in sexual reproduction in clonal plants in a homogeneous environment: physiological integration between ramets within clones. Our results are vital for better understanding the adaptation of populations and even the evolution of species of clonal plants.

Characteristics of yield components and population quality in high-nitrogen- utilization wheat cultivars

<p indent="0mm">In the rice-wheat rotation system, 24 and 23 wheat cultivars were separately planted in Yangzhou and Suining of Jiangsu province in 2016–2017 and 2017–2018. According to nitrogen utilization rate (NUR), these cultivars were clustered into three groups, i.e., NUR-H (NUR ≥ 50%), NUR-M (NUR 40%–50%), and NUR-L (NUR ≤ 40%), to identify the differences in grain yield, yield components, and population quality, which would provide a reference for cultivar selection for high-yield and high-efficiency in wheat production. Yangmai 25 and Ningmai 21 in Yangzhou and Huaimai 35 in Suining showed NUR-H phenotypes in consecutive two years. Grain yield of the NUR-H cultivars was more than <sc>6500 kg</sc> hm^–2 in Yangzhou and <sc>7000 kg</sc> hm^–2 in Suining, which were significantly higher than those of NUR-M and NUR-L groups. NUR-H group had more spikes, and it grains per spike and 1000-grain weight were not significantly different from those of the other groups. Grain yield and spikes number were significantly positively correlated with NUR among different cultivars. More stem and tiller number, higher percentage of fertile tillers and higher leaf area index (LAI) at the milk-ripening stage were shown in the NUR-H group. A higher dry matter accumulation at stages of booting, anthesis, and maturity, after anthesis, and in the vegetative organs at maturity were found in the NUR-H group. However, there were no differences in dry matter remobilization and harvest index among different cultivars. Number of stems and tillers at booting and anthesis, LAI at the milk-ripe stage, and dry matter accumulation at each stage after anthesis, and in the vegetative organs at maturity were significantly positively correlated with NUR in the all cultivar in two sites. A vigorous tillering capacity at the early growing phase and a higher LAI and photosynthetic production at the late growth stages could be observed in NUR-H cultivars, resulting in more photosynthate for grain-filling. Furthermore, the critical parameters of cultivar screening for high-yield and high-efficiency in wheat following rice were proposed, that is <sc>16,000–20,000 kg</sc> hm^–2 dry matter accumulation at maturity and <sc>4100–6700 kg</sc> hm^–2 dry matter accumulation after anthesis.

The Optimal Image Date Selection for Evaluating Cultivated Land Quality Based on Gaofen-1 Images.

This study proposes a method for determining the optimal image date to improve the evaluation of cultivated land quality (CLQ). Five vegetation indices: leaf area index (LAI), difference vegetation index (DVI), enhanced vegetation index (EVI), normalized difference vegetation index (NDVI), and ratio vegetation index (RVI) are first retrieved using the PROSAIL model and Gaofen-1 (GF-1) images. The indices are then introduced into four regression models at different growth stages for assessing CLQ. The optimal image date of CLQ evaluation is finally determined according to the root mean square error (RMSE). This method is tested and validated in a rice growth area of Southern China based on 115 sample plots and five GF-1 images acquired at the tillering, jointing, booting, heading to flowering, and milk ripe and maturity stage of rice in 2015, respectively. The results show that the RMSEs between the measured and estimated CLQ from four vegetation index-based regression models at the heading to flowering stage are smaller than those at the other growth stages, indicating that the image date corresponding with the heading to flowering stage is optimal for CLQ evaluation. Compared with other vegetation index-based models, the LAI-based logarithm model provides the most accurate estimates of CLQ. The optimal model is also driven using the GF-1 image at the heading to flowering stage to map CLQ of the study area, leading to a relative RMSE of 14.09% at the regional scale. This further implies that the heading to flowering stage is the optimal image time for evaluating CLQ. This study is the first effort to provide an applicable method of selecting the optimal image date to improve the estimation of CLQ and thus advanced the literature in this field.

Relationship between photosynthesis, bleeding-sap mass, and bleeding components in maize hybrids and corresponding parents in northern China

Currently, the main maize production areas in northeastern China are facing soil fertility loss, which severely affects root growth and limits photosynthesis. It is widely acknowledged that physiological conditions of the root system are closely related to the photosynthetic capacity; therefore, we evaluated whether there are certain differences in root bleeding sap characteristics and photosynthetic capacity between the hybrids and their parents. The results showed that heterosis of the photosynthetic capacity occurred at the milk-ripe stage; however, heterosis of bleeding-sap mass (BSM) and organic biomass occurred during the whole growth period. Photosynthetic rate correlated positively with BSM and the bleeding components; a similar trend was also observed between BSM and bleeding components. These data suggested that appropriate water and fertilizer supply can improve the photosynthesis-related parameters and yield of maize.

Biology and Management of the New Zealand Endemic Wheat Bug, Nysius huttoni (Hemiptera: Lygaeidae)

Abstract The wheat bug, Nysius huttoni White, mainly reported as a pest of wheat and forage brassicas, is native to New Zealand. This pest has been accidentally introduced into The Netherland and Belgium during apple exports from New Zealand. The bug population is abundant in open sparse vegetations and hot-dry habitats, and feeds on dropping seeds. It damages wheat grains during milk-ripe stage by piercing through the glumes into the developing grains that can reduce gluten protein and reduce baking quality. Bugs also suck phloem fluid from seedlings, which can reduce plant establishment in forage brassicas. Early scouting and field monitoring are suggested before making pest management decisions. Seed treatment with neonicotinoids, permethrin, and chlorpyrifos spray in the standing crops are chemical methods of management in New Zealand. These conventional synthetic pesticides have nontarget effects on human health, the environment, and biodiversity. However, preventive measures such as the use of less-susceptible cultivars, and using potential trap crops is other important pest management options. Alyssum (Lobularia maritima L. Desv. Brassicales: Brassicaceae) and wheat (Triticum aestivum L. Poales: Poaceae) are two potential trap crops of wheat bug. Kale (Brassica oleracea L.) cultivars, such as Corka and Regal, and wheat (Triticum aestivum) cultivars, such as Batten, Domino, and Oroua, are less-susceptible cultivars. Understanding the biology and ecology of the pest, and utilizing preventative pest management measures such as the use of trap crops and less-susceptible cultivars, and integrating these with ‘soft’ chemicals make a suitable integrated pest management strategy for this pest.

Influence of different nitrogen forms application on rice photosynthesis: fluorescence with water-saving irrigation in black soil region of Songnen Plain, Northeast China

In order to study the response of the rice photosynthetic-fluorescence characteristics to the application of different nitrogen forms with water-saving irrigation, by using LI-6400XT-type photosynthetic apparatus and other equipment, the fluorescence parameters, stomatal resistance and photosynthetic-CO2 response curves of rice were measured at the critical stages under water-saving irrigation methods. Results showed that the change trend of ETR and photochemical fluorescence quenching coefficient (Qp) with different nitrogen forms were declining–rising–declining. Compared with CK (control treatment), ETR and Qp with NO3− treatment were better than the others, which indicated that this treatment was most advantageous to increasing ETR. The electron flow from PSII oxidation-lateral to PSII was enhanced. The potential quantum efficiency (Fv/Fm) was the lowest at tillering stage and the highest at heading stage. Compared with CK, at heading stage, Fv/Fm with NO3−, NH4+ NO3− and NH4+ treatments was increased by 1.68, 0.61 and 1.81%, respectively, while NO3− and NH4+ played a more important role in promoting the ability to capture light. The change trend of non-photochemical fluorescence quenching coefficient with different treatments was not obvious. During the growth period, the stomatal resistance (Rs) was changed dynamically, reaching the second peak at the jointing stage and the highest peak at the milk-ripe stage, and both were higher than CK. The Rs of different nitrogen forms was as NH 4 + > NH4+NO 3 − > NO3−, which showed that with different nitrogen forms, Rs of NO3− treatment was low, stomatal opening was correspondingly greater than the other nitrogen forms, and under the same moisture conditions, this treatment of stomatal opening was more beneficial for gas exchange and external CO2 flowing into the leaf cells, which could increase photosynthetic physiological response. By fitting the parameters of photosynthetic-CO2 response curve, it was concluded that the photorespiration rate (RP) was greater than CK, but it was different for three nitrogen treatments during different periods. Rice light saturation point and apparent carboxylation efficiency (α) of NO3− treatment during three growth periods were more uniform, indicating that this treatment had a higher utilization rate for low concentration of CO2. Maximum photosynthetic rate (Pmax) with NO3− and NH4+ treatments of the three growth periods was 29.396–31.208 and 28.969–31.371, respectively. The CO2 compensation point and curve angle (θ) had no stable trend during the whole growth period. Therefore, the nitrogen forms could influence the photosynthetic characteristics of the rice leaves, and the result can provide theoretical guidance and scientific basis for increasing the efficiency of nitrogen utilization.

Screening of barley genotypes for drought tolerance based on culm reserves contribution to grain yield

Grain filling determines the grain weight, a major component of grain yield in cereals. Grain filling in barley depends on current assimilation and culm reserves. A pot experiment was conducted at the Grilled House, Department of Crop Botany, Bangladesh Agricultural University, Mymensingh during October 2015–May 2016 to study the grain filling patterns and the contributions of culm reserves to grain yield under drought stress. The experiment consisted of two factors—barley cultivars (six cultivars) and drought stress treatments (control and drought stress). Drought stress was imposed by limiting the irrigation during grain filling period. The tillers were sampled at anthesis, milk-ripe and maturity to determine the changes in dry weights of different parts, viz., leaf lamina, culm with sheath, spikes, and grains; and to examine the contribution of culm reserves to grain yield. The result in this experiment revealed that the grain yield was reduced by 5–25% due to drought stress. The reduction in grain yield was attributable to reduce number of grains per spike and lighter grain weight due to the stress. Drought stress drastically reduced the grain filling duration by about 30% and the stress induced early leaf senescence. Photosynthesis rate and leaf greenness were also reduced in stress. The stress altered the contribution of culm reserves, water soluble carbohydrates (WSCs) in culms to grains. At milk ripe stage, accumulation reached its peak. It accumulated 29.0 to 70.0 mg and from 15.8 to 40.6 mg culm−1 in control and stressed plants, respectively. The residual culm WSCs ranged from 3.5 to 11.2 mg and 1.0 to 3.5 mg culm−1 under control and stress conditions, respectively. The highest contribution of culm WSCs to grain yield was observed in BARI barley2 and the lowest was in BARI barley5 both in control and stress condition. Among the cultivars studied, BARI barley2 produced higher yield with the higher contribution of culm reserves to grain yield under the drought stress.J. Bangladesh Agril. Univ. 16(1): 62-66, April 2018

Cytosolic APX2 is a pleiotropic protein involved in H2O2 homeostasis, chloroplast protection, plant architecture and fertility maintenance.

Rice cytoplasmic APX2 is a pleiotropic protein, densely distributed around chloroplasts. It plays key roles in H2O2 homeostasis and chloroplast protection, and is related to plant architecture and fertility regulation. Ascorbate peroxidases (APXs) catalyze the conversion of H2O2 into H2O. In this report, we systematically investigated the function of cytosolic APX2 using a T-DNA knockout mutant. Loss of OsAPX2 altered rice architecture including shoot height and leaf inclination, resulting in shoot dwarfing, leaf dispersion and fertility decline. Sixty-five differentially expressed proteins were identified in flag leaves of the milk-ripe stage, mainly involved in photosynthesis, glycolysis and TCA cycle, redox homeostasis, and defense. The absence of APX2 severely impacted the stability of chloroplast proteins, and dramatically reduced their expression levels. Subcellular localization showed that APX2 was enriched around each chloroplast to form a high concentration sphere, highlighting chloroplasts as key targets protected by the protein. Accumulation of H2O2 was suppressed in the KO-APX2 mutant, which may benefit from increased CAT activity and functional complementation of APX family members. Unexpectedly, the accumulation of soluble sugar, especially sucrose increased significantly, suggesting that APX2 was involved in regulation of sugar metabolism. Obviously, roles of the cytosolic APX2 are very profound and complex in rice. It can be concluded that the cytosolic APX2 is a pleiotropic protein and an important regulator in ROS homeostasis, chloroplast protection, carbohydrate metabolism as well as plant architecture and fertility maintenance.

Effects of harvest time and added molasses on nutritional content, ensiling characteristics and in vitro degradation of whole crop wheat.

ObjectiveWheat is an alternative to corn silage for ruminant feeding in northern China. This study examined the effects of harvest time and added molasses on nutritional content, ensiling characteristics and in vitro degradation of whole crop wheat (WCW).MethodsFresh WCW at the milk-ripe stage was harvested at 0700 h (i.e., in the morning [Mo]) and 1700 h (i.e., in the afternoon [Af]), and then immediately used to prepare silage and make hay. Commercial molasses was added to Af WCW at 0%, 2%, 4%, and 6% (fresh weight) proportions. The WCW treated with molasses was mixed thoroughly prior to ensiling.ResultsDry matter (DM), neutral detergent fiber, water soluble carbohydrate (WSC) content (p<0.01), accumulative gas production in 72 h (GP72h, 77.46 mL/g vs 95.15 mL/g) and dry matter disappearance in vitro (69.15% vs 76.77%) were lower (p<0.05), while crude protein (CP) content was higher for WCW silage (WCWS) compared to WCW (p<0.01). The propionic acid and butyric acid concentrations in WCWS from Mo WCW were 1.47% and 0.26%, respectively. However, the propionic and butyric acid concentrations were negligible, while the ammonia nitrogen/total nitrogen (NH3-N/TN, p<0.01) concentration was lower and the rate of gas production at 50% of the maximum (17.05 mL/h vs 13.94 mL/h, p<0.05) was higher for Af WCWS compared to Mo WCWS. The incubation fluid’s NH3-N concentration was lower in WCWS and Af WCW compared to Mo WCW (p<0.05). The CP and WSC content increased with increasing molasses levels (p<0.05). Furthermore, the pH (p<0.01) and time when gas production was 50% of the maximum (2.78 h vs 3.05 h, p<0.05) were lower in silage treated with 4% molasses than silage without molasses.ConclusionHarvesting wheat crops in the afternoon and adding molasses at 4% level to WCW optimally improved ensiling characteristics, leading to well-preserved silage.