Root system architecture and seed weight relations in forage pea (Pisum sativum ssp. arvense L. Poir.)

ABSTRACT: Forage pea (Pisum sativum ssp. arvense (L.) Poir.) is an important legume crop for fresh and dry herbage production with high input costs as irrigation and fertilization. Selection and breeding of accessions for improved drought tolerance, water, and mineral uptake efficiency become a necessity, rather than a choice. This study evaluated a set of forage pea accessions for the seedling root system architecture diversity and seed reserve utilization, under controlled conditions. Eight cultivars and an elite breeding line were evaluated for the first time in a plexiglass system. The number and lengths of the roots in each depth zone (0, 5, 10, 15+ cm) were evaluated and significant diversity was identified. The cultivar Livioletta had the highest number of roots and total root length. There was a significant correlation between seed weight, seed reserve utilization ratio, and root system vigor. Accessions with the highest seed reserve utilization had the highest total root length and numbers. Seedling root system vigor seems to be effective in predicting the fate of the accessions through maturity. The results suggested a possibility of “seedling root selection” for forage crop breeding.

Characterization of Root System Architecture Traits in Diverse Soybean Genotypes Using a Semi-Hydroponic System

Phenotypic variation and correlations among root traits form the basis for selecting and breeding soybean varieties with efficient access to water and nutrients and better adaptation to abiotic stresses. Therefore, it is important to develop a simple and consistent system to study root traits in soybean. In this study, we adopted the semi-hydroponic system to investigate the variability in root morphological traits of 171 soybean genotypes popularized in the Yangtze and Huaihe River regions, eastern China. Highly diverse phenotypes were observed: shoot height (18.7–86.7 cm per plant with a median of 52.3 cm); total root length (208–1663 cm per plant with a median of 885 cm); and root mass (dry weight) (19.4–251 mg per plant with a median of 124 mg). Both total root length and root mass exhibited significant positive correlation with shoot mass (p ≤ 0.05), indicating their relationship with plant growth and adaptation strategies. The nine selected traits contributed to one of the two principal components (eigenvalues > 1), accounting for 78.9% of the total genotypic variation. Agglomerative hierarchical clustering analysis separated the 171 genotypes into five major groups based on these root traits. Three selected genotypes with contrasting root systems were validated in soil-filled rhizoboxes (1.5 m deep) until maturity. Consistent ranking of the genotypes in some important root traits at various growth stages between the two experiments indicates the reliability of the semi-hydroponic system in phenotyping root trait variability at the early growth stage in soybean germplasms.

Interactive Impact of Biochar and Arbuscular Mycorrhizal on Root Morphology, Physiological Properties of Fenugreek (Trigonella foenum-graecum L.) and Soil Enzymatic Activities

Arbuscular mycorrhizal fungi (AMF) inoculation and biochar amendment has been reported to improve the growth of several crop plant; however, their role in stress amelioration individually as well as in combination has not been worked out. Limited information is available about the synergistic use of biochar and Arbuscular Mycorrhizal Fungi (AMF). Here, we investigated the synergistic effect of biochar and AMF on plant development, root architecture, the physiological performance of fenugreek (Trigonella foenum-graecum), and soil enzymatic activities. Biochar and AMF were shown to have a considerable effect on plant height, according to the data (53.3 and 66.6%, respectively), leaf number (22.5 and 45.1%), total root length (19.8 and 40.1%), root volume (32.1 and 71.4%), chlorophyll a content (26.0 and 17.8%), chlorophyll b content (50.0 and 28.9%), total chlorophyll content (30.0 and 18.1%), and carotenoid content (60.0 and 48.0%) over the control treatment. There was a considerable increase in plant height when biochar and AMF were combined together by 80.9%, total root length by 68.9%, projected area by 48.7%, root surface area by 34.4%, root volume by 78.5%, chlorophyll a content by 34.2%, chlorophyll b content by 68.4%, total chlorophyll content by 44.5%, and carotenoid content by 84.0% compared to the control. Our results recommend that the combination of biochar and AMF is advantageous in fenugreek growth, microbial biomass, and soil enzyme activities.

Sorghum Drought Tolerance is Associated with Deeper Root System and Decreased Transpiration Rate

Drought decreases grain yield of sorghum [Sorghum bicolor (L.) Moench], and understanding the mechanism(s) related to drought tolerance is critical for sustaining sorghum production. Variation in root and shoot traits associated with drought tolerance were analyzed to provide an integrated view of factors that underlie the drought tolerance of sorghum. The plants were grown in the root column up to the five-leaf stage, then exposed to either 0.9 fraction of transpirable soil water (FTSW) or 0.4 FTSW for five days. In another experiment, at the five-leaf stage, stress was imposed for 14 days. Various root and shoot traits associated with drought tolerance were recorded. The seminal root angle of IS13540 was lower (24.4) than IS23143 (42.6). Drought stress increased the maximum root length (40%) and total root length (58%) of IS13540 than its irrigated control. In contrast, the maximum root length and total root length were decreased in IS23143. Similarly, across the lines, drought stress decreased stomatal conductance (37%), transpiration rate (42%), photosynthetic rate (40%), photosystem II quantum yield (20%), photochemical quenching (44%), and total dry matter production (34%) than irrigated control. An increased transpiration rate was observed in IS23143 than IS13540 under irrigated and drought stress. In IS23143, the reduction in photosynthetic rate under drought may be a combination of stomatal and non-stomatal factors. However, in IS13540, the reduction is especially by the stomatal factors. It is evident that IS13540 is a drought-tolerant line, and tolerance is related to a deep prolific root system and reduced tran-spiration rate.

Estimation of the efficiency of rooting varieties of Berberis Thunbergia DC. by the method of green shearing

In this work, the results of evaluating the differences in the variants of the three-factor experiment on rooting of varieties of Barberry Thunberg (Berberis thunbergii DC.) By factors: varietal characteristics, the number of nodes and the use of a root formation regulator are considered. The study involved cuttings of the following varieties: ‘Dart’s Red Lädy’, ‘Kobold’, ‘Golden Ring’, ‘Harlequin’, ‘Rosetta’, ‘Red Chief’ and ‘Aurea’. 4- (indol-3-yl) butyric acid (trademark "Kornevin") was used as a root formation stimulator by the method of dusting. The green cuttings had 2 and 3 knots. The results of analysis of variance on the variability of the average total root length in green cuttings depending on varietal characteristics, dusting with a root formation stimulator and the number of nodes made it possible to establish that the ‘Red Chief’ variety had the maximum average total root length and was significantly different from all other varieties. The average total length of roots when using a root formation stimulator is significantly higher than in the control variant. Cuttings with three nodes reliably had a large average total root length. Based on the results obtained, it is assumed that the use of a root formation stimulator and rooting of cuttings with three nodes has a positive effect on the rooting processes of barberry cuttings. Keywords: BERBERIS THUNBERGII, THUNBERG BARBERRY, GREEN CUTTINGS, 4- (INDOL-3-YL) BUTYRIC ACID, KORNEVIN, KNOTS

Elevated carbon dioxide and temperature effects on rooting behaviour of grape cuttings

An experiment was laid out to study the impact of eCO2 (550ppm), eT (+3ºC) and their interaction (eCO2+eT) on rooting behaviour of cuttings of three grape varieties- Thompson Seedless, Bangalore Blue, and Dogridge in FATE and OTC facilities. Observations were recorded at 50 and 80 days after planting (DAP) and root growth data was recorded and analysed using WinRHIZO root scanner and its software. Analysis revealed that, among the selected grape varieties, Thompson Seedless cuttings has shown highest number of roots, root volume and dry biomass under eCO2 and eCO2+ eT conditions, while total root length and root length density were highest with Bangalore Blue. Under eT condition, Bangalore Blue showed highest number of roots, total root length and root length density, while root volume and dry biomass was highest with Thompson Seedless. The per se values of root parameters under all conditions and their response to eCO2 was lowest with Dogridge. Though eT condition reduced all the root parameters, their performance improved under eCO2+ eT indicating the presence of higher concentration of CO2 reduced the ill effects of high temperature. Overall, eCO2 and eCO2+eT conditions improved root parameters of grape varieties, while eT reduced them as compared to their performance under ambient condition and varietal variation is significant.

Graphene promotes plant root growth by enhancing root respiration

To explore the effects of graphene on plant root growth and development, 25 mg/L graphene were used to treat the seedling roots of 48 plant species. These results showed that the total root length of the plants was decreased when cultured by hydroponics method. Whereas the total root length of plant species cultured by soil showed different growth effects, among which the ratio of promotion effect was 69.77%, the ratio of inhibition effect was 11.63% and the no-effect ratio was 18.60%. To gain insights into the molecular mechanisms by which graphene presents different growth effects on the root length, we performed RNA-seq for 32 plant roots treated with 25 mg/L graphene. We totally identified 90,259 DEGs in 32 plant species, among which 55,537 were graphene-induced and 34,722 were graphene-repressed. KEGG pathway enrichment analysis indicated that 43 pathways were assigned to these enriched differentially expressed genes in response to the graphene treatment. Top enriched pathways include starch and sucrose metabolism, glycolysis/gluconeogenesis, pyruvate metabolism, the citrate cycle (TCA cycle), phenylpropanoid biosynthesis, glutathione metabolism, endocytosis, peroxisome etc. The gene expressions of these pathway were induced or repressive in plant roots showing promotion or inhibitory effects, respectively. Accumulation of antioxidant enzyme as well as enhanced respiration might lead to the increasing plant root length. In addition, transcriptome and TEM data showed that graphene enters plant root cells by endocytosis. These results uncovered molecular level influences of graphene on plant roots development.

Effects of NaCl treatment on root system activity of the euhalophyte Aksora

For the purpose of study the relationship between the characteristics of the root system, activity and saline pressure of Aksora (Suaeda salsa Pall.) various concentrations of NaCl (0, 200, 400 and 600 mmol/L) were prepared. The effect of salt concentration on the biomass of Aksora (Suaeda salsa Pall.) root and the activity of the root system was studied. The results showed that as the NaCl concentration increased, the dry and fresh weight of the Aksora (Suaeda salsa Pall.) roots, the total length and surface area of the root increased and then gradually decreased. The highest values of dry weight, fresh weight and total length of the vascular system were observed at a concentration of 200 mmol / L NaCl, while at a concentration of 600 mmol/L NaCl, the dry weight, wet weight and total root length, and surface area signifi cantly decreased. These results indicate that refi nement of Aksora with higher concentrations of NaCl salt can increase the total length and absorption area of roots, thereby promoting root growth and adaptability to saline pressure. However, it has been found that with extrmely high salt concentrations inhibit root growth by reducing the total root length and absorption area. Key words: Aksora, vascular activity, NaCl, absorption zone.

Phenotypic Diversity for Root Traits and Identification of Superior Germplasm for Root Breeding in Watermelon

Root traits are an important component for productive plant performance. Roots offer immediate absorptive surfaces for water and nutrient acquisition and are thus critical to crop growth and response to biotic and abiotic stresses. In addition, roots can provide the first line of defense against soilborne pathogens. Watermelon crop performance is often challenged by inclement weather and environmental factors. A resilient root system can support the watermelon crop’s performance across a diverse range of production conditions. In this study, 335 four-day-old watermelon (Citrullus spp.) seedlings were evaluated for total root length, average root diameter, total root surface area, and total root volume. Total root length varied from 8.78 to 181 cm (20.6-fold variation), total surface area varied from 2 to 35.5 cm2, and average root diameter and total root volume had an 8- and 29.5-fold variation, respectively. Genotypes PI 195927 (Citrullus colocynthis) and PI 674448 (Citrullus amarus) had the largest total root length values. Accessions PI 674448 and PI 494817 (C. amarus) had the largest total root surface area means. Watermelon cultivars (Citrullus lanatus) had a relatively smaller root system and significantly fewer fibrous roots when compared with the roots of the other Citrullus spp. Positive genetic correlations were identified among total root length, total root surface area, and total root volume. This genetic information will be useful in future breeding efforts to select for multiple root architecture traits in watermelon. Germplasm identified in this study that exhibit superior root traits can be used as parental choices to improve watermelon for root traits.

Localized and Moderate Phosphorus Application Improves Plant Growth and Phosphorus Accumulation in Rosa multiflora Thunb. ex Murr. via Efficient Root System Development

Roots have high plasticity with the ability to adapt to heterogeneous nutrient distribution, but little is known about the effects of phosphorus (P) supply methods and levels on Rosa multiflora Thunb. ex Murr. root growth and nutrient accumulation. A pot study was conducted with two P supply methods (mixed and localized application) and three levels (P-deficient, P-moderate and P-adequate). The results showed that with localized application, P-deficient and P-moderate treatments significantly improved total root length, total surface area, total length of fine roots, shoot DW and total P accumulation in Rosa multiflora compared with their respective mixed application at 45 days after being transplanted (DAT) and 92 DAT; for P-adequate supply, the same trends were observed at 45 DAT, but not at 92 DAT. At 92 DAT, with localized application, when P levels increased from P-deficient to P-moderate, total P accumulation increased by 43.3%; but when P levels increased from P-moderate to P-adequate, no effect was observed. Furthermore, higher P accumulation in leaves was observed in localized P-moderate condition; decreased P uptake per root dry weight and greater root/shoot ratio were observed in localized P-adequate at 92 DAT. Total P accumulation was positively correlated with total root length and root surface area (R2: 0.68~0.94). There was a significant interaction effect among treatment days, P supply methods and levels (p ≤ 0.05) on shoot DW, root DW, root/shoot ratio and total P accumulation. These findings indicated that localized and moderate P supply appear efficient for improving R. multiflora growth and P accumulation via efficient root system development.