Characterizing the Utility of the Root-to-Shoot Ratio in Douglas-Fir Seedling Production

Nursery-grown tree seedlings are a vital component of successful restoration and reforestation programs, useful when calls for increased planting for industrial forest management are made, and a tool for climate change mitigation. One of the most extensively planted and studied trees in Western North America is Douglas-fir. Building on that body of work, this review was conducted to identify if the root-to-shoot ratio (root:shoot, R:S), a commonly referred-to metric in reforestation planning, yields meaningful guidance for producing seedlings that are better able to establish across a variety of field conditions. The results indicated that there is wide variability in R:S of nursery-grown seedlings. The relationship between R:S and subsequent root growth and seedling survival varies depending on Douglas-fir variety, seedling stocktypes, and site conditions. The biological and physiological basis for using R:S remains, and likely could be used to enhance seedling quality; however, there is an ongoing need for planning and collaboration between researchers and practitioners to identify how to best deploy this evaluation tool.

Seed Hardening in Relation to Seedling Quality Characters of Green Gram (Vigna radiata L.)

Background: Green gram is a drought resistant crop requires low inputs. The productivity of mung bean is very low. Initial germination, growth and vigour are some major reasons of low productivity. The present investigation was carried out to study the effect of seed hardening on morpho-physiological and seedling quality characters in green gram. Methods: The green gram var. GAM-5 was imposed with seed hardening treatments viz., 2% CaCl2, 500 ppm Cycocel, 1000 ppm Cycocel, 25 ppm NAA, 50 ppm NAA, water soaked control and absolute control. The treated seeds along with control were evaluated for their seedling quality characters under laboratory conditions. Result: The study reported that seeds hardened with CaCl2 @ 2% recorded higher germination per cent, root, shoot and seedling length, fresh weight, turgor weight, dry weight and seed vigour index I and II. Seed hardened with 50 ppm NAA reported higher root dry weight and root to shoot ratio on dry weight basis while Cycocel 1000 ppm treatment recorded higher root to shoot ratio on length basis. The treatments CaCl2 2% followed by Cycocel 1000 ppm were found to be superior as compared to other treatments and control on the basis of lab studies.

Water Deficit and Recovery-Induced Changes in Growth, Photosynthetic Characteristics, Antioxidant Enzymes and Yield of Two Tartary Buckwheat Genotypes

Tartary buckwheat (Fagopyrum tataricum) is an important food crop that is widely adaptable to hostile environments. In this study the responses of two Tartary buckwheat genotypes: drought-susceptible Chuanqiao No. 1 (CQ) and drought-tolerant Jingqiao No. 2 (JQ) in terms of morphology, photosynthesis, physiology and yield to a progressive water deficit and recovery treatment (WD-R) were evaluated. Plants in the well-watered (WW) treatment were watered throughout the experiment. Compared to the WW treatment, water deficit in the WD-R treatment caused decreases in plant height, stem diameter, branch number, stem node number, biomass, seed number, soil water content (SWC), leaf relative water content (RWC), net photosynthesis rate (Pn), intercellular CO2 concentration, stomatal conductance (Gs), transpiration rate (Tr) and Fv/Fm in both CQ and JQ plants. Leaf wilting, malondialdehyde content, superoxide dismutase activity, peroxidase activity, initial fluorescence (F0) and root-to-shoot ratio were significantly increased under water stress in the WD-R treatment. Under the WD-R treatment, compared to CQ, JQ maintained higher RWC, SWC, Pn, Gs, WUE, Fv/Fm, plant height, branch number, stem node number, root biomass, stem biomass, leaf biomass, total biomass, root-to-shoot ratio, seed number per plant, and yield, but a lower Tr and F0. By correlation analysis, Gs was positively correlated with leaf RWC and SWC. These differential growth indexes, biochemical traits and physiological responses might be useful for understanding drought-tolerance genotypes that can grow under water-deficit conditions with minimum yield loss. © 2021 Friends Science Publishers

Biomass Functions and Carbon Content Variabilities of Natural and Planted Pinus koraiensis in Northeast China

The population of natural Korean pine (Pinus koraiensis) in northeast China has sharply declined due to massive utilization for its high-quality timber, while this is vice versa for Korean pine plantations after various intensive afforestation schemes applied by China’s central authority. Hence, more comprehensive models are needed to appropriately understand the allometric relationship variations between the two origins. In this study, we destructively sampled Pinus koraiensis from several natural and plantation sites in northeast China to investigate the origin’s effect on biomass equations. Nonlinear seemingly unrelated regression with weighted functions was used to present the additivity property and homogenize the model residuals in our two newly developed origin-free (population average) and origin-based (dummy variable) biomass functions. Variations in biomass allocations, carbon content, and root-to-shoot ratio between the samples obtained from plantations and natural stands were also investigated. The results showed that (1) involving the origin’s effect in dummy variable models brought significant improvement in model performances compared to the population average models; (2) incorporating tree total height (H) as an additional predictor to diameter at breast height (D) consistently increase the models’ accuracy compared to using D only as of the sole predictors for both model systems; (3) stems accounted for the highest partitioning proportions and foliage had the highest carbon content among all biomass components; (4) the root-to-shoot ratio ranged from 0.18–0.35, with plantations (0.28 ± 0.04) had slightly higher average value (±SD) compared to natural forests (0.25 ± 0.03). Our origin-based models can deliver more accurate individual tree biomass estimations for Pinus koraiensis, particularly for the National Forest Inventory of China.

Influence of Atomization Nozzles and Spraying Intervals on Growth, Biomass Yield, and Nutrient Uptake of Butter-Head Lettuce under Aeroponics System

The atomized nutrient solution droplet sizes and spraying intervals can impact the chemical properties of the nutrient solution, biomass yield, root-to-shoot ratio and nutrient uptake of aeroponically cultivated plants. In this study, four different nozzles having droplet sizes N1 = 11.24, N2 = 26.35, N3 = 17.38 and N4 = 4.89 µm were selected and misted at three nutrient solution spraying intervals of 30, 45 and 60 min, with a 5 min spraying time. The measured parameters were power of hydrogen (pH) and electrical conductivity (EC) values of the nutrient solution, shoot and root growth, ratio of roots to shoots (fresh and dry), biomass yield and nutrient uptake. The results indicated that the N1 presented significantly lower changes in chemical properties than those of N2, N3 and N4, resulting in stable lateral root growth and increased biomass yield. Also, the root-to-shoot ratio significantly increased with increasing spraying interval using N1 and N4 nozzles. The N1 nozzle also revealed a significant effect on the phosphorous, potassium and magnesium uptake by the plants misted at proposed nutrient solution spraying intervals. However, the ultrasonic nozzle showed a nonsignificant effect on all measured parameters with respect to spraying intervals. In the last, this research experiment validates the applicability of air-assisted nozzle (N1) misting at a 30-min spraying interval and 5 min of spraying time for the cultivation of butter-head lettuce in aeroponic systems.

Challenges in estimating forest biomass: use of allometric equations for three boreal tree species

Regionally fitted allometric equations for individual trees and root-to-shoot ratio values are normally used to estimate local aboveground and belowground forest biomass, respectively. However, uncertainties arising from such applications are poorly understood. We developed equations for both aboveground and belowground biomass using destructive sampling for three dominant upland boreal tree species in northwestern Alberta, Canada. Compared with our equations, the diameter-based national equations derived for use across Canada underestimated aboveground biomass for Picea glauca (Moench) Voss but gave reasonable estimates for Populus balsamifera L. and Populus tremuloides Michx. The national equations based on both tree diameter and height overestimated aboveground biomass for the Populus species but underestimated it for Picea glauca in our study area. The approach of root-to-shoot ratio proposed by the Intergovernmental Panel on Climate Change (IPCC) overestimated belowground biomass by 16%–41%, depending on forest cover type, in comparison with our values estimated directly on site, with the greatest bias in deciduous-dominated stands. When the general allometric equations for aboveground biomass and the root-to-shoot ratio for belowground biomass were combined to estimate stand biomass, overestimation could be as high as 18% in our study area. The results of our study support the development of improved regional allometric equations for more accurate local-scale estimations. Incorporating intraspecific variation of important traits such as tree taper may be especially helpful.

Assessment of Pruning and Controlled-release Fertilizer to Rejuvenate Huanglongbing-affected Sweet Orange

Previous research has shown that Huanglongbing {HLB [causal agent Candidatus Liberibacter asiaticus (CLas)]}-affected sweet orange (Citrus sinensis) trees have a reduced root-to-shoot ratio, potentially due to the high rate of root death. The diminished root system cannot support the existing aboveground canopy and a cycle of imbalance begins. As a result, the tree enters into a continuous carbohydrate stress cycle and, eventually, the tree declines. Therefore, the goal of this study was to evaluate pruning as a strategy to adjust the root-to-shoot ratio to improve growth and productivity of HLB-affected trees. In Jan. 2015, a 3-year trial was initiated on a 14-year-old grove of ‘Hamlin’ sweet orange on Swingle citrumelo (Citrus paradisi × Poncirus trifoliate) rootstock that was symptomatic of HLB and produced less than 180 lb of fruit per tree. The four pruning treatments were as follows: 1) 0% pruning (no canopy removal), 2) 25% pruning (canopy removed), 3) 50% pruning (canopy removed), and 4) 80% pruning (canopy removed). In a split-plot design, two sources of fertilizer were evaluated in combination with the pruning: 1) conventional fertilizer [CNV (dry granular)] applied at 200 lb/acre nitrogen (N) in five split applications per year, and 2) controlled-release fertilizer (CRF) applied at 150 lb/acre N, split in three applications per year. Within each pruning treatment, half of the trees received CNV and the other half received CRF. The fertilizer treatments were applied in each of the 3 years; however, pruning was performed only once in the beginning of the experiment. The trees that were pruned produced new vegetative growth that looked healthy with no visual HLB symptoms (initially); however, the trees remained positive for CLas throughout the study as determined by quantitative real-time polymerase chain reaction. The 80% pruned trees grew vigorously over the course of 3 years but remained significantly smaller in canopy than control trees (0% pruning) for both CRF and CNV treatments. The 25% and 50% pruned tree canopies grew back and were similar in canopy size as 0% pruning (control) treatment by the end of year 2. At the end of the study, the use of CRF on 25% pruned trees resulted in a significantly higher leaf area index as compared with trees receiving CNV. A significant positive linear correlation was observed between canopy volume and root density; the root density decreased with intensive pruning. A significant positive correlation was also observed between canopy volume and yield, and a negative correlation between canopy volume and fruit drop. There were no significant increases in yield resulting from any pruning or fertilization treatments compared with controls (0% pruning). However, with the use of CRF, the amount of N and frequency of application were reduced. Overall, our results indicate that pruning did not improve the productivity of HLB-affected trees over the course of 3 years. Therefore, severe pruning is not a viable option to rejuvenate the HLB-affected trees.

USE OF GLIRICIDIA-ENRICHED LIQUID ORGANIC FERTILIZER FOR PRODUCTION OF CAISIM (Brassica juncea L.)

Green biomass is one of major nutrient source and determines the quality of liquid organic fertilizer (LOF), including Gliricidia sepium (Jacq.) Kunth ex Walp. An experiment was conducted to study the effects of Gliricidia-enriched LOF on growth and yields of caisim, arranged in randomized complete design with three replicates. Treatments consisted of six LOF concentrations, 0%, 20%, 40%, 60%, 80% and 100%. Results indicated that concentration of gliricidia-LOF significantly influenced leaf greenness and shoot fresh weight, but not root to shoot ratio and shoot water content. Concentrations of gliricidia-LOF increased leaf greenness and shoot fresh weight of caisim. The optimum concentration was 70.85% to produce weight of 73 grams caisim per plant. Root to shoot ratio was not significantly different. Although treatments did not affect shoot water content, all caisim water content was on average above 90 %.