The Role of Outer Membrane Protein(s) Harboring SLH/OprB-Domains in Extracellular Vesicles’ Production in Synechocystis sp. PCC 6803

Cyanobacteria are a group of photosynthetic prokaryotes that contribute to primary production on a global scale. These microorganisms release vesicles to the extracellular environment, spherical nanosized structures, derived essentially from the outer membrane. Even though earlier works in model Gram-negative bacteria have hypothesized that outer membrane stability is crucial in vesicle formation, the mechanisms determining vesicle biogenesis in cyanobacteria remain unknown. Here, we report on the identification of six candidate genes encoding outer membrane proteins harboring SLH/OprB-domains in the genome of the model cyanobacterium Synechocystis sp. PCC 6803. Using a genetics-based approach, one gene was found to encode an essential protein (Slr1841), while the remaining five are not essential for growth under standard conditions. Vesicle production was monitored, and it was found that a mutant in the gene encoding the second most abundant SLH/OprB protein in Synechocystis sp. PCC 6803 outer membrane (Slr1908) produces more vesicles than any of the other tested strains. Moreover, the Slr1908-protein was also found to be important for iron uptake. Altogether, our results suggest that proteins containing the SLH/OprB-domains may have dual biological role, related to micronutrient uptake and to outer membrane stability, which, together or alone, seem to be involved in cyanobacterial vesicle biogenesis.

Removal of Biomass and Nutrients by Weeds and Direct-Seeded Rice under Conservation Agriculture in Light-Textured Soils of North-Western India

The escalating scarcity of irrigation water, transplantation of rice on light-textured soils and labour cost acted as major drivers for the transition towards direct-seeded rice (DSR) cultivation from the conventionally flooded transplanting system. Despite these advantages, DSR is a challenge in light texture soil due to heavy weed infestation and a slight decline in crop yield. The weeds compete for nutrients and have an adverse effect on the growth and yield of crops. Hence, to assess the removal of macro and micronutrients by weeds and direct-seeded rice, a field experiment was carried out on sandy loam soil for two consecutive Kharif seasons (2018 and 2019). Three treatments from rice, namely: DSR under zero tillage (DSR-ZT), DSR under conventional tillage (DSR-CT) and DSR under reduced tillage (DSR-RT) were taken as main plots with three tillage treatments in wheat, namely: Conventional tillage without rice straw (CTW-R), Zero tillage without rice straw (ZTW-R) and Zero tillage with straw as mulch using Happy Seeder (ZTW+R) as subplots, replicated thrice. Among the rice establishment methods, DSR-RT showed an edge in terms of rice grain and straw yield (6.18 and 8.14 Mg ha−1, respectively) as well as macro- and micronutrient uptake by rice. Under management practices, ZTW+R proved as an efficient strategy in terms of yield and nutrient uptake by crops. The contribution of weeds towards biomass production was maximum under the ZTW-R (9.44%) treatment followed by DSR-ZT (7.72%). The nutrient budgeting showed that macro- and micronutrient removal by weeds was minimum under reduced tillage (24.51 and 50.35%, respectively), whereas it was 21.88 and 44.87% when wheat was grown under conventional tillage without rice straw. In overall, the research study concluded that weeds on an average remove 25.65 % macronutrients (N, P, K) and 51.47% of micronutrients (Zn, Cu, Fe and Mn) in DSR under rice-wheat cropping system.

Effect of Integrated Potassium Application on Growth, Yield and Micronutrient Uptake by Forage Maize (Zea mays L.)

A pot experiment was conducted during kharif season of 2019 to carry out the study on “Interactive effect of potash (K2O), potassium mobilizing bacteria (KMB) and FYM on forage yield, nutrient uptake by forage maize and soil fertility in a loamy sand soil of middle Gujarat”. Application of K2O @ 60 kg ha-1, KMB and FYM recorded significantly the highest plant height of forage maize at harvest over respective control. Crop fertilized with K2O @ 60 kg ha-1 and KMB gave significantly the highest green forage and dry matter yield. The results indicated that application of K2O @ 60 kg ha-1, potassium mobilizing bacteria recorded significantly the highest uptake of N, P, K, Fe and Zn by crop at harvest. Significantly the highest uptake of N, K and Cu were found with application of FYM @10 t ha-1. Significantly the highest K uptake by maize as well as higher P and Zn uptake by maize were observed due to interaction effect of K × KMB (60 kg K2O ha-1 with KMB). In case of N and Cu uptake by maize were noted the Significantly higher due to interaction effect of K × KMB (30 kg K2O ha-1 with KMB) and K × KMB × FYM (60 kg K2O ha-1 with KMB and FYM), respectively. The integrated use of potassium fertilizers along with KBM or in combination with FYM significantly improved the maize grain and nutrient uptake.

Cross-Talks Between Macro- and Micronutrient Uptake and Signaling in Plants

In nature, land plants as sessile organisms are faced with multiple nutrient stresses that often occur simultaneously in soil. Nitrogen (N), phosphorus (P), sulfur (S), zinc (Zn), and iron (Fe) are five of the essential nutrients that affect plant growth and health. Although these minerals are relatively inaccessible to plants due to their low solubility and relative immobilization, plants have adopted coping mechanisms for survival under multiple nutrient stress conditions. The double interactions between N, Pi, S, Zn, and Fe have long been recognized in plants at the physiological level. However, the molecular mechanisms and signaling pathways underlying these cross-talks in plants remain poorly understood. This review preliminarily examined recent progress and current knowledge of the biochemical and physiological interactions between macro- and micro-mineral nutrients in plants and aimed to focus on the cross-talks between N, Pi, S, Zn, and Fe uptake and homeostasis in plants. More importantly, we further reviewed current studies on the molecular mechanisms underlying the cross-talks between N, Pi, S, Zn, and Fe homeostasis to better understand how these nutrient interactions affect the mineral uptake and signaling in plants. This review serves as a basis for further studies on multiple nutrient stress signaling in plants. Overall, the development of an integrative study of multiple nutrient signaling cross-talks in plants will be of important biological significance and crucial to sustainable agriculture.

Waste to resource: use of water treatment residual for increased maize productivity and micronutrient content

Soil degradation, which is linked to poor nutrient management, remains a major constraint to sustained crop production in smallholder urban agriculture (UA) in sub-Saharan Africa (SSA). While organic nutrient resources are often used in UA to complement mineral fertilizers in soil fertility management, they are usually scarce and of poor quality to provide optimum nutrients for crop uptake. Alternative soil nutrient management options are required. This study, therefore, evaluates the short-term benefits of applying an aluminium-based water treatment residual (Al-WTR), in combination with compost and inorganic P fertilizer, on soil chemical properties, and maize (Zea mays L.) productivity and nutrient uptake. An eight-week greenhouse experiment was established with 12 treatments consisting of soil, Al-WTR and compost (with or without P fertilizer). The co-amendment (10% Al-WTR + 10% compost) produced maize shoot biomass of 3.92 ± 0.16 g at 5 weeks after emergence, significantly (p < 0.05) out-yielding the unamended control which yielded 1.33 ± 0.17 g. The addition of P fertilizer to the co-amendment further increased maize shoot yield by about twofold (7.23 ± 0.07 g). The co-amendment (10% Al-WTR + 10% C) with P increased maize uptake of zinc (Zn), copper (Cu) and manganese (Mn), compared with 10% C + P. Overall, the results demonstrate that combining Al-WTR, compost and P fertilizer increases maize productivity and micronutrient uptake in comparison with single amendments of compost and fertilizer. The enhanced micronutrient uptake can potentially improve maize grain quality, and subsequently human nutrition for the urban population of SSA, partly addressing the UN’s Sustainable Development Goal number 3 of improving diets.

Effect of Boron on Nutritional Quality of Groundnut Grown in Coastal Sandy Soils

Aim: To study the effect of boron on quality parameters and micronutrient uptake of groundnut in coastal sandy soils. Study Design: The experiment laid out in randomized block design with three replications. Place of Study: At College Farm, Agricultural College, Bapatla, Guntur. Methodology: After the preliminary layout, the TAG-24 variety of groundnut was used as a test crop, with a spacing of 30 cm x 10 cm in the experimental site. Plant samples were collected at 45, 90 DAS, and harvest. Plant samples were shade dried and kept in hot air oven at 75°C until a constant weight was obtained. Samples were powdered and then analysed for micronutrients using standard chemical procedures. Results: Protein content, boron content and uptake of micronutrients viz., iron, zinc, manganese, copper and boron were significantly improved with the application of boron in groundnut. Oil content and oil yield were not significantly influenced by the application of boron. The highest value of all these parameters were recorded in T4 (RDF + soil application of Borax @ 12.5 kg/ha). Conclusion: Application of boron along with RDF improved the nutritional quality of groundnut in coastal sandy soils.

EFFECT OF DIFFERENT BORON SOURCES AND LEVELS ON MACRO AND MICRONUTRIENT UPTAKE AND POST-HARVEST AVAILABILITY IN SALINE SODIC SOIL

The study was conducted to assess the effect of different boron sources and levels of macro and micronutrient uptake andpostharvest availability in saline sodic soil. Four levels of B (0, 0.5, 1.0 and 1.5 mg kg-1) was supplied through three different sources, namely borax, sodium octaborate and magnesium boro humate complex. A total of twelve treatment combinations were laidin factorial CRD design with three replications. Cotton var. LRA5166 was chosen as the test crop. The results revealed that application of 1.5 mg B kg-1 as magnesium boro humaterecorded the highest NPK uptake of 3.05, 0.99 and 2.55 g pot-1, respectively and the highest mean Zn, Fe, Mn and Cu uptake of 8.78, 13.69, 5.93 and 1.84 mg pot-1, respectively.The available NPK and other micronutrient status in post-harvest soil were invariably not influenced by the source and levels of the boron sources.

Assessing Yield Response and Relationship of Soil Boron Fractions with Its Accumulation in Sorghum and Cowpea under Boron Fertilization in Different Soil Series

Boron (B) is an essential micronutrient in the growth of reproductive plant parts. Its deficiency and/or toxicity are widespread in arid and semi-arid soils with low clay contents. This study was planned to determine the response of sorghum (Sorghum bicolor L., non-leguminous crop) and cowpea (Vigna sinensis L., leguminous crop) to boron (0, 2, 4, and 16 µg g−1) on four distinct soil series from Punjab, Pakistan i.e., Udic Haplustalf (Pindorian region), Typic Torrifluvent (Shahdra region), Halic Camborthid (Khurianwala region), and Udic Haplustalf (Gujranwala region). Overall, there was a significant difference (p < 0.05) in yield between the sorghum (3.8 to 5.5 g pot−1 of 5 kg dry soil) and cowpea (0.2 to 3.2 g pot−1 of 5 kg dry soil) in response to B application. The highest yield was observed in both sorghum and cowpea either in control or at 2 µg g−1 B application in all four soils. Cowpea showed the same yield trend in all four soils (i.e., an increase in yield at 2 µg g−1 B application, followed by a significant decrease at the higher B levels). In contrast, sorghum exhibited greater variability of response on different soils; Udic Haplustalf (Pindorian region) produced the greatest yield at low levels of B application. However, Halic Camborthid produced its lowest yield at that level. Boron concentration in shoots increased with the levels of B application, particularly in sorghum. In cowpea, the plant growth was extremely retarded—and most of the plants died at higher levels of B application even if a lower concentration of B was measured within the shoot. Hot water-extractable B was the most available fraction for cowpea (R2 = 0.96), whereas the easily exchangeable B was most available for sorghum (R2 = 0.90). Overall, these results have implications for micronutrient uptake for both leguminous and non-leguminous crops.

Calcium, Magnesium and Micronutrient Uptake in Watercress (Nasturtium officinale) under Arsenic and Salinity Stress Conditions

Heavy metals are elements that mainly have a 5-22 gr.cm-3 specific gravity. Some of these metals are essential micronutrients for plant growth (Such as Zinc (Zn), Copper (Cu), Manganese (Mn), Nickel (Ni) and Cobalt (Co)). Some other heavy metals, have a high toxicity properties such as Lead (Pb), Cadmium (Cd) and Mercury (Hg). In order to investigate the potential of watercress (Nasturtium officinale) in the uptake of elements from nutrient solutions with different salinities, a factorial experiment was conducted in a completely randomized design with three replications in the greenhouse. In this experiment, different levels of arsenic were zero, 5, 10, 20, 40, 40, 80 and 160 mg.L-1, which were obtained from sodium arsenate source and added to Epstein’s nutrient solution to obtain the mentioned concentrations. The salt concentration of the nutrient solution was 0, 10, 20, 40 and 80 mM which was prepared from sodium chloride source and added to Epstein solution. After making nutrient solutions with different salinity and concentrations, watercress was cultivated. The ANOVA results showed that the interaction of salinity and arsenic levels on the calcium, magnesium, iron, manganese, zinc and copper concentrations in watercress was significant at the level of one percent probability. The highest concentrations of these elements were obtained in the levels without salinity and arsenic and the lowest values were obtained in the 80 mM salinity levels and 160 mg.l-1 arsenic.

Carbon Nanodots Derived from Kitchen Waste Biomass as a Growth Accelerator for Fenugreek Plant

Herein, we report the utilization of kitchen waste biomass as a source of carbonaceous material for carbon nanodots synthesis and its application as a plant growth regulator in agricultural crops. The water soluble carbon dots (CDs) were synthesized by pyrolysis of kitchen derived waste tea residue (WTR) and used in the field of agriculture nanotechnology. Herein, we have explored the effect of different concentrations of WTR-CDs (10, 30 and 50 mg/L) on growth of FG with respect to various plant growth parameters. It was observed that the WTR-CDs has positive effect on all plant growth parameters investigated and also assist for micronutrient uptake which is confirmed by AAS and zeta potential measurement. UV light, Fluorescence spectroscopy, and confocal fluorescence microscopy examination were employed for the understanding of uptake and transport route of WTR-CDs in FG plant through absorption of WTR-CDs by root as well as seed coat along with water. Therefore, the growth of FG was a significant increase in quality of the plant which appears to be effective and no serious side effects were seen during the study.