Brassinosteroids Mitigate Cadmium Effects in Arabidopsis Root System without Any Cooperation with Nitric Oxide

The heavy metal cadmium (Cd) affects root system development and quiescent center (QC)-definition in Arabidopsis root-apices. The brassinosteroids-(BRs)-mediated tolerance to heavy metals has been reported to occur by a modulation of nitric oxide (NO) and root auxin-localization. However, how BRs counteract Cd-action in different root types is unknown. This research aimed to find correlations between BRs and NO in response to Cd in Arabidopsis’s root system, monitoring their effects on QC-definition and auxin localization in root-apices. To this aim, root system developmental changes induced by low levels of 24-epibrassinolide (eBL) or by the BR-biosynthesis inhibitor brassinazole (Brz), combined or not with CdSO4, and/or with the NO-donor nitroprusside (SNP), were investigated using morpho-anatomical and NO-epifluorescence analyses, and monitoring auxin-localization by the DR5::GUS system. Results show that eBL, alone or combined with Cd, enhances lateral (LR) and adventitious (AR) root formation and counteracts QC-disruption and auxin-delocalization caused by Cd in primary root/LR/AR apices. Exogenous NO enhances LR and AR formation in Cd-presence, without synergism with eBL. The NO-signal is positively affected by eBL, but not in Cd-presence, and BR-biosynthesis inhibition does not change the low NO-signal caused by Cd. Collectively, results show that BRs ameliorate Cd-effects on all root types acting independently from NO.

Mechanism of Intermittent Deep Tillage and Different Depths Improving Crop Growth From the Perspective of Rhizosphere Soil Nutrients, Root System Architectures, Bacterial Communities, and Functional Profiles

Long-term conventional shallow tillage reduced soil quality and limited the agriculture development. Intermittent deep tillage could effectively promote agricultural production, through optimizing soil structure, underground ecology system, and soil fertility. However, the microecological mechanism of intermittent deep tillage promoting agriculture production has never been reported, and the effect of tillage depth on crop growth has not been explored in detail. In this study, three levels of intermittent deep tillage (30, 40, and 50 cm) treatments were conducted in an experimental field site with over 10 years of conventional shallow tillage (20 cm). Our results indicated that intermittent deep tillage practices helped to improve plant physiological growth status, chlorophyll a, and resistance to diseases, and the crop yield and value of output were increased with the deeper tillage practices. Crop yield (18.59%) and value of output (37.03%) were highest in IDT-50. There were three mechanisms of intermittent deep tillage practices that improved crop growth: (1) Intermittent deep tillage practices increased soil nutrients and root system architecture traits, which improved the fertility and nutrient uptake of crop through root system. (2) Changing rhizosphere environments, especially for root length, root tips, pH, and available potassium contributed to dissimilarity of bacterial communities and enriched plant growth-promoting species. (3) Functions associated with stress tolerance, including signal transduction and biosynthesis of other secondary metabolites were increased significantly in intermittent deep tillage treatments. Moreover, IDT-30 only increased soil characters and root system architecture traits compared with CK, but deeper tillage could also change rhizosphere bacterial communities and functional profiles. Plant height and stem girth in IDT-40 and IDT-50 were higher compared with IDT-30, and infection rates of black shank and black root rot in IDT-50 were even lower in IDT-40. The study provided a comprehensive explanation into the effects of intermittent deep tillage in plant production and suggested an optimal depth.

THE EFFECT OF PRE-PLANTING TREATMENT OF SEEDLINGS WITH BACTERIAL STRAINS ON THE VEGETATIVE REPRODUCTION OF GARDEN STRAWBERRIES

In field experiments of the strawberry queen bee, it was found that pre-planting treatment of the root system of seedlings with bacterial biopreparation Phytop 8.67, at a concentration of 1×105 CFU/ml, as well as its tank mixture with humic preparation Phoenix, 0.05% gave the greatest efficiency – stimulation of vegetative reproduction of plants by 3.9-4.9 rosettes /plant (by 24-32 %) relative to control was observed. At the same time, it should be noted that the effect of the tank mixture Phytop 8.67, 1×105 CFU/ml + Phoenix, 0.05 % statistically significantly (P<0.05) exceeded all other options for stimulating vegetative reproduction of plants.

The effects of different compositions of growth media on the development of microplants of the Solnechny potato variety

The results of studying the effect of nutrient media of various compositions on the growth of improved micro-plants of potatoes of the Solnechny variety grown under laboratory conditions in vitro are presented. Six compositions of the nutrient medium were studied: standard Murashige-Skuga medium modified for micropropagation (considered as a control), modified Murashige-Skuga medium with a reduced content of mineral components (up to 1/2 and up to 1/3), modified Murashige-Skuga medium with an increased content of agar-agar (10 g/l), modified Murashige-Skuga medium with a reduced content of agar-agar (4 g/l), Murashige-Skuga medium modified with the addition of 3 mg/L giberrellinic acid and 1 mg/L indoliacetic acid. The following parameters of cultivated plants were taken into account: plant length, root presence, number of internodes, total plant mass, leaf mass, root mass, leaf plate surface area. The use of modified nutrient media with a reduced content of mineral components led to an increase in plant length (by 28-30%), stem mass (by 25%) due to leaf mass (by 18%) and stem mass (by 31%) and the total surface area of leaf plates (by 12%). In the variant using a medium with 1/3 mineral components an increase in the mass of the root system was observed (by 20%). When growing plants on a modified nutrient medium with a high content of agar-agar, a decrease in the length of plants (by 6%), a decrease in the mass of the scion (by 12%) due to a decrease in the mass of the stem (by 15%) was observed. Plants grown on a modified nutrient medium with a reduced content of agar-agar were distinguished by a larger mass of the root system (by 10%), scion (by 17%) (due to an increase in leaf mass (by 27%), as well as the total surface area of leaf plates (by 22%). When growth regulators (giberrellin and indoliacetic acid) were added to the modified nutrient medium, a significant increase in plant height (by 70%), a decrease in the mass of the root system (by 50%) and leaves (by 46%), and an increase in the mass of the stem (by 23%) were observed. The total leaf surface area was 28% lower than the control values. For accelerated micropropagation of improved potato plants of the Solnechny variety and preparation of plants for transplanting to aerohydroponic systems in order to produce mini-tubers, the following modified nutrient media are optimal options: with a reduced number of mineral components (1/2 and 1/3) and with a reduced content of agar-agar.

Parameterization of Mangrove Root Structure of Rhizophora stylosa in Coastal Hydrodynamic Model

Mangroves are able to attenuate tsunamis, storm surges, and waves. Their protective function against wave disasters is gaining increasing attention as a typical example of the green infrastructure/Eco-DRR (Ecosystem-based Disaster Risk Reduction) in coastal regions. Hydrodynamic models commonly employed additional friction or a drag forcing term to represent mangrove-induced energy dissipation for simplicity. The well-known Morison-type formula (Morison et al. 1950) has been considered appropriate to model vegetation-induced resistance in which the information of the geometric properties of mangroves, including the root system, is needed. However, idealized vegetation configurations mainly were applied in the existing numerical models, and only a few field observations provided the empirical parameterization of the complex mangrove root structures. In this study, we conducted field surveys on the Iriomote Island of Okinawa, Japan, and Tarawa, Kiribati. We measured the representative parameters for the geometric properties of mangroves, Rhizophora stylosa, and their root system. By analyzing the data, significant correlations for hydrodynamic modeling were found among the key parameters such as the trunk diameter at breast height (DBH), the tree height H, the height of prop roots, and the projected areas of the root system. We also discussed the correlation of these representative factors with the tree age. These empirical relationships are summarized for numerical modeling at the end.

WUSCHEL-related homeobox family genes in rice control lateral root primordium size

The development of a plastic root system is essential for stable crop production under variable environments. Rice plants have two types of lateral roots (LRs): S-type (short and thin) and L-type (long, thick, and capable of further branching). LR types are determined at the primordium stage, with a larger primordium size in L-types than S-types. Despite the importance of LR types for rice adaptability to variable water conditions, molecular mechanisms underlying the primordium size control of LRs are unknown. Here, we show that two WUSCHEL-related homeobox (WOX) genes have opposing roles in controlling LR primordium (LRP) size in rice. Root tip excision on seminal roots induced L-type LR formation with wider primordia formed from an early developmental stage. QHB/OsWOX5 was isolated as a causative gene of a mutant that is defective in S-type LR formation but produces more L-type LRs than wild-type (WT) plants following root tip excision. A transcriptome analysis revealed that OsWOX10 is highly up-regulated in L-type LRPs. OsWOX10 overexpression in LRPs increased the LR diameter in an expression-dependent manner. Conversely, the mutation in OsWOX10 decreased the L-type LR diameter under mild drought conditions. The qhb mutants had higher OsWOX10 expression than WT after root tip excision. A yeast one-hybrid assay revealed that the transcriptional repressive activity of QHB was lost in qhb mutants. An electrophoresis mobility shift assay revealed that OsWOX10 is a potential target of QHB. These data suggest that QHB represses LR diameter increase, repressing OsWOX10. Our findings could help improve root system plasticity under variable environments.