Lateral Root Dry Weight Research Articles

Effects of altitude and varieties on overwintering adaptability and cold resistance mechanism of alfalfa roots in the Qinghai-Tibet Plateau.

The roots are the main functional organs involved in the overwintering adaptability of alfalfa (Medicago sativa). However, it is still unclear how the roots are involved in the cold resistance in the high-altitude area of the Qinghai-Tibet Plateau (QTP). In this study, three winter-surviving 2-year-old alfalfa varieties (M.sativa Zhongmeng No.1, M.sativa Chiza No.1, and M.sativa Gongnong No.1) planted at two different altitudes (2812 m and 3109 m) in the northeast edge of the QTP were used to explore the cold-resistance mechanism. At low altitudes (2812 m), the overwintering rate, taproot length, root area, root surface area, and root average diameter, plant height, fresh yield and hay yield of M.sativa Zhongmeng No.1 were significantly higher (P < 0.01) than for the other two varieties. At high altitude (3109 m), lateral root length, number of lateral roots, main root dry weight, and lateral root dry weight of M.sativa Chiza No.1 were higher (P < 0.01) than the other two varieties. At low and high altitudes, the activities of peroxidase and catalase were higher (P < 0.05) in M.sativa Chiza No.1 during post-winter and pre-winter respectively. At low altitude, higher soluble sugar (P < 0.05) and proline (P < 0.01) contents were recorded during the pre- and post-winter periods. Membership function analysis showed that M.sativa Zhongmeng No.1 has the strongest cold resistance. The structural equation model showed that the overwintering rate of alfalfa was mainly affected by the morphological characteristics of roots and the physiological characteristics of roots, with contribution rates of 0.54 and 0.75 respectively, and the physiological characteristics of roots had the greatest effect on the overwintering rate. This study is of great significance to effectively solve the overwintering of alfalfa, the lack of high-quality legume forage resources, and promote the development of animal husbandry in the alpine areas of the QTP. © 2022 Society of Chemical Industry.

Cavity Size and Copper Root Pruning Affect Production and Establishment of Container-Grown Longleaf Pine Seedlings

Abstract With six container types, we tested the effects of cavity size (i.e., 60, 93, and 170 ml) and copper root pruning on the root system development of longleaf pine (Pinus palustris Mill.) seedlings grown in a greenhouse. We then evaluated root egress during a root growth potential test and assessed seedling morphology and root system development 1 year after planting in central Louisiana, USA. Seedling size was increased by copper root pruning in small cavities but was unaffected by this treatment in larger cavities. Before planting, copper root pruning increased taproot and secondary lateral root dry weights at the expense of primary lateral root dry weight and increased root growth potential in the top 5 cm of the root plug. Across treatments, survival was 97%, and all seedlings were in the grass stage. Of the lateral root dry weight that elongated during the first year after planting, 33% more occurred in the upper 5 cm of soil when seedlings were treated with copper. Within each cavity size, copper root pruning did not affect the general morphology of 1-year-old seedlings. However, relationships between root collar diameter and root egress by depth indicated that this treatment has the potential to increase the range of cavity sizes used for seedling production.

Root Growth Parameters of Converted Race Stocks of Upland Cotton and Two BC2F2 Populations

Genetic modification of the rooting system may lead to more drought tolerant upland cotton, Gossypium hirsutum L. This experiment was designed to evaluate rooting traits at the seedling stage for 68 Converted Race Stocks (CRS) compared with TAM94L‐25 and ‘Lankart 142’, and to investigate the recoverability of robust rooting traits in two BC2F2 populations derived by crossing a robust (M‐9044‐0031) and a nonrobust (M‐9044‐0057) rooting CRS donor parent with TAM94L‐25. Initial screen of the CRS showed that genetic variation occurred among the 68 accessions for root length (RL), lateral root number (LRN), root fresh weight (RFW), lateral root dry weight (LRDW), and total root dry weight (TRDW). There was a 2.3‐, 2.6‐, 4.6‐, 4.8‐, and 4.4‐fold difference among the 11 most robust and 11 least robust rooting CRS accessions for RL, LRN, RFW, LRDW, and TRDW, respectively. However, no CRS were identified that were superior to the elite germplasm and BC2F2 recurrent parent, TAM94L‐25. The robust rooting population of M‐9044‐0031/3*TAM94L‐25 produced longer RL and more LRN per plant than the nonrobust rooting population of M‐9044‐0057/3*TAM94L‐25. However, no differences were observed between the two BC2F2 populations for root weight parameters. Results suggest that the day‐neutral CRS accessions have useful genetic variability for root growth parameters, that robustness of seedling rooting parameters can be recovered easily, and that seedling rooting robustness can be improved by crossing robust rooting parents.

Growth Enhancement of Container-grown Pawpaw Seedlings as Influenced by Media Type, Root-zone Temperature, and Fertilization Regime

Pawpaw [Asimina triloba (L.) Dunal] is a native American fruit tree that has potential as a new fruit crop or for use in landscapes, but little information is available to nurseries on the production of containerized plants. In greenhouse experiments, growth of pawpaw seedlings in Rootrainers was examined in three fertilization regimes, two root-zone temperatures, and four substrates [ProMix, 6 pine bark: 1 sand (v/v), 1 sand: 1 sphagnum peat, and 4 pine bark: 1 sand: 1 sphagnum peat medium]. A similar germination rate of 80% was obtained in all substrates. Weekly fertigation treatments were imposed when seedlings had 2 to 3 leaves, at 0, 50, and 100 mg·L-1 N as Peters 20N-8.6P-16.6K water-soluble fertilizer plus soluble trace elements. After 140 days at the highest fertilizer rate, plant height, leaf number, and dry weight (roots, shoots, and total plant) were greater in ProMix and 1 sand:1 sphagnum peat than in 6 pine bark: 1 sand (v/v) or 4 pine bark: 1 sand: 1 sphagnum peat. Also, the root: shoot ratio was lower in ProMix and 6 pine bark: 1 sand (v/v). Overall, plant biomass production was greater in ProMix than in 6 pine bark: 1 sand (v/v). In a separate experiment, bottom heat (32 ± 0.3 °C) hastened seedling emergence from ProMix by 9 days compared to ambient root-zone conditions (24 ± 0.2 °C). An average seedling height of 10 cm was attained by ambient plants 79 days after sowing, whereas seedlings with bottom heat reached this height after 69 days. Seedlings subjected to bottom heat had increased leaf number (30%), plant height (32%), whole plant leaf area (94%), shoot dry weight (104%), root dry weight (50%), lateral root dry weight (125%), and total plant dry weight (87%). Seedlings with bottom heat had a reduction in root: shoot ratio of 25% and in specific leaf dry weight of 16% compared to ambient plants. Seedlings subjected to bottom heat had a higher leaf chlorophyll (chl) concentration of chl a (39%), chl b (33%), chl p (43%), total chl (38%), and chl a: b ratio (8%) than seedlings grown without bottom heat. Pawpaw seedling growth was best using ProMix with 100 mg·L-1 N Peters applied once weekly, or using ProMix with bottom heat and 50 mg·L-1 N Peters applied twice per week.

Incident Irradiance and Cupric Hydroxide Container Treatment Effects on Early Growth and Development of Container-grown Pawpaw Seedlings

The North American pawpaw [Asimina triloba (L.) Dunal] has great potential as a fruit crop or as a landscape plant. The influence of incident irradiance on pawpaw seedling growth and development in containers was examined in the greenhouse and outdoors. Root spiraling can be a problem for container-grown pawpaw seedlings; therefore, the influence of paint containing cupric hydroxide [Cu(OH)2] at 100 g·L-1 applied to the interior of containers on plant growth was also examined in a greenhouse environment. In pawpaw seedlings grown outdoors for 11 weeks, low to moderate shading levels of 28%, 51%, or 81% increased leaf number, total leaf area, and total plant dry weight (DW) compared to nonshaded seedlings. A shading level of 81% decreased the root to shoot ratio by half compared to nonshaded plants. Shading of 98% reduced leaf number, leaf size, and shoot, root, and total plant DW. Shading increased leaf chlorophyll a and b concentrations for pawpaw seedlings grown outdoors, while it decreased average specific leaf DW (mg·cm-2). In a separate greenhouse experiment, pawpaw seedlings subjected to shade treatments of 0%, 33%, 56%, 81%, or 98% did not respond as greatly to shading as plants grown outdoors. Greenhouse-grown plants had greater total and average leaf area under 33% or 56% shading than nonshaded plants; however, shading &gt;56% reduced root, shoot, and total plant DW. Total shoot DW was greater in greenhouse grown plants with 33% shading compared to nonshaded plants. Pawpaw seedlings in control and most shade treatments (33% to 81%) in the greenhouse environment had more leaves and greater leaf area, as well as larger shoot, root, and total plant DW than seedlings in similar treatments grown outdoors. The greenhouse environment had a 10% lower irradiance, a 60% lower ultraviolet irradiance, and a significantly higher (1.23 vs. 1.20) red to far-red light ratio than the outdoors environment. Treatment of container interiors with Cu(OH)2 decreased total and lateral root DW in nonshaded seedlings, and it adversely affected plant quality by causing a yellowing of leaves and reduction of chlorophyll levels by the end of the experiment in shaded plants. Growth characteristics of pawpaw seedlings were positively influenced by low to moderate shading (28% or 51%) outdoors and low shading (33%) in the greenhouse. Seedlings did not benefit from application of Cu(OH)2 to containers at the concentration used in this study. Commercial nurseries can further improve production of pawpaw seedlings using low to moderate shading outdoors.

Comparison of acid and alkaline soil and liquid culture growth systems for studies of shoot and root characteristics of white lupin (Lupinus albus L.) genotypes

Current agronomic cultivars of white lupin (Lupinus albus L.) in the European Union are intolerant of calcareous soils, producing poor yields. Intolerant genotypes of L. albus, and a tolerant genotype of L. pilosus Murr. were grown in liquid culture varied for pH, or pot and chamber soil systems varied for lime. Chlorosis, determined visually as leaf interveinal yellowing, was shown to be an unsuitable genotype screen. However, leaf greenness measured electronically at a sub-chlorotic level, provided a quantifiable estimate of stress. Shoot Ca concentration increased when plants were grown in the limed compared with non-limed soil, but remained unchanged between the liquid culture treatments. The root systems in the pots and liquid culture showed growth abnormalities, whereas important differences between L. albus and L. pilosus root systems were seen in the soil chambers. The tap and lateral root dry weights of both species were lower in the limed soil than in the non-limed soil. The dry weight per plant of the cluster roots was comparable between the treatments in both species, although when grown in the limed soil they accounted for a larger proportion of the L. albus root system. In contrast, the proportion of the root system that was cluster root in L. pilosus was comparable between the treatments. In limed soil, both species showed increased levels of extractable citrate from the soil adhering to the cluster roots compared with that in the acid-pH soil. However this did not result in higher shoot P concentrations in the limed compared with acid-soil grown plants. These results demonstrated the importance of analysing a developed and unrestricted root system when determining the physiological responses of these species to limed soil.

The effect of soil liming on shoot development, root growth, and cluster root activity of white lupin

The effects of a limed soil upon root and shoot growth of white lupin (Lupinus albus L.) were investigated using soil tubes and pots. After 75 days in the soil tubes, the combined taproot and lateral root dry weight in limed soil (2.5% CaO w/w) was significantly less than in neutral pH soil (by 57%). However, the dry weight and numbers of cluster roots remained comparable between the treatments, demonstrating for the first time that the cluster roots respond differently to the rest of the root system. Cluster roots accounted for 17% of the total root biomass in neutral soil, increasing significantly to over 30% in limed soil. When grown for 43 days in pots containing soil with different additions of lime (0.5–2.5% CaO w/w), soil citrate concentrations were higher than in the neutral pH soil treatment in all except the 2.5% lime treatment, in which they were lower. In both experiments, shoot dry weights were lower in the presence of the limed soil compared with those in the neutral pH soil. Although a reduction in shoot dry weight was not apparent at 21 days in the limed-soil tubes, the initiation of fewer mainstem leaf primordia indicated a slower shoot development than occurred in the neutral soil. Plants grown in the limed-soil tubes showed leaf yellowing and some chlorosis within 9 days. At the final harvest, the shoot phosphorus and manganese concentrations were significantly lower in plants grown in limed soil compared with those in the neutral pH soil, whereas the concentration of calcium was higher.

Modeling the effects of nitrogen on components of coca yield

Estimating yields (leaf dry weights) of Erythroxylum coca var. coca Lam. (coca) in regions where there is no access requires a method that can be used remotely. A simulation model that characterizes coca growth under varying weather conditions offers such a method. To develop this model, crop response to its environment must be quantified. The current experiment examined how a range in nitrogen (N) availability affected N status of various parts of the coca plant and components of yield. Minimal and maximal values for N concentration in leaves, stems, and roots were determined and N status calculated. Young leaves (a small yield component) had the highest N concentration, the greatest demand for N, and snowed the greatest N stress. Old leaves had the next highest N concentration and a high demand for N, but showed the lowest N stress. Nitrogen status in old leaves was most affected by N availability. Dry weights of each leaf type increased with increased N availability, but leaf cocaine concentration was not affected. Stems and taproots had the lowest N concentrations and these were not affected by N availability. Lateral roots, closer to the source of N, had N concentrations that reflected N availability, however lateral root dry weights were not affected by N supply. Increased N availability increased (a) the number of growing points on the plant, (b) the number of leaves per growing point, and (c) the size of old leaves. Increases in these components translate into increased yields. Leaf yields correlated with the N status of leaves (r=0.58, p≤0.001), but variability in leaf yields for a given N status was too high to have strong predictive power.

Early Growth and Development of Pawpaw [Asimina triloba (L.) Dunal] Seedlings in the Greenhouse as Influenced by Shade and Root-zone Modification

This experiment was designed to determine the optimal light level for growing pawpaw seedlings in the greenhouse. In addition, we wanted to determine if modifying the root-zone would positively impact pawpaw seedling growth and development. Experimental treatments were imposed from seed sowing until the plants were destructively harvested. The experimental design was a split-plot, where blocking was done by position in the greenhouse. The main plot of the experiment was shade. This was accomplished by growing seedlings under a wooden frame covered with shadecloth to reduce incident light intensity received by the plant by 30%, 55%, 80%, or 95%. The control treatment was 0% shade or ambient greenhouse light level. The split-plot was root-zone modification. Half of all growing containers were untreated (control) while the other half were painted with SpinOut™, a commercially available product used to reduce root spiraling in nursery containers. There were 40 replicate seedlings per experimental treatment combination per block. Seedling shoot length and unfolded leaf number was recorded twice a week from seedling emergence until destructive harvest. Whole-plant leaf area was also determined. Leaves, stems, and tap and lateral roots were separated and dried to determine biomass partitioned to the respective organs. Up to 55% shade did not significantly reduce whole-plant biomass, while plants at 80% and 95% shade were stunted. Shade in the greenhouse is not required as was previously thought. Specific leaf mass and lateral root mass decreased as shade increased. Neither tap or lateral root dry weights were significantly affected by root-zone modification. New recommendations for container production of pawpaws in the greenhouse will be discussed.

Seasonal ectomycorrhizal fungal biomass development on loblolly pine (Pinus taeda L.) seedlings

Ergosterol, a membrane sterol found in fungi but not in plants, was used to estimate live mycelial biomass in ectomycorrhizae. Loblolly pine (Pinus taeda L.) seeds were sown in April 1993 and grown with standard nursery culture practices. Correlations between total seedling ergosterol and visual assessment of mycorrhizal colonization were high during July and August but low as ectomycorrhizal development continued into the growing season. Percentages of mycelial dry weight over lateral roots decreased from 9% in July to 2.5% in November because seedling lateral root dry weight accumulated faster than mycelial dry weight. Total ergosterol per seedling increased from July through February. As lateral root dry weight ceased to increase during winter months, ectomycorrhizal mycelia became the major carbohydrate sink of pine seedlings. No distinctive seasonal pattern of soil ergosterol content was observed. The impact of ectomycorrhizal fungi on plant carbohydrate source-sink dynamics can be quantitatively estimated with ergosterol analysis but not with conventional visual determination.

The growth of shoots and lateral roots of Quercus robur L. seedlings following simulated undercutting

The effect of cutting the tap root on shoot growth and development of lateral roots was observed in seedling Quercus robur L. growing in PVC tubes containing peat and perlite. Cutting the tap root had little effect on shoot height and leaf number although some treatments caused a significant but slight reduction in shoot dry weight and number of branches. Total root dry weight was similar in control and treated plants but distributed differently between the types of root present. The tap root always formed the largest part of the total root dry weight. In control plants most lateral root dry weight was in roots 1 mm diameter. Development of the root system following root cutting was similar for all treatments: new long laterals > 1 mm diameter with relatively few branches, that formed replacement tap roots, developed near the cut end of the original tap root. Fine laterals (< 1 mm diameter) near the root collar continued to grow forming highly branched systems.

The effect of seaweed concentrate on the growth of Pinus pinea seedlings

Seedlings of Pinus pinea L. growing in plastic containers were treated with seaweed concentrate (SWC). Different concentrations of SWC were applied, 0 to 3 times, to the roots or shoots of the seedlings. Shoot application increased plant weight mainly by increasing shoot growth. This was manifested as increased shoot length and weight and a decrease in the root/shoot ratio. Root drenches did not change the total plant weight but it accelerated root growth and increased lateral root dry weight. Root growth capacity (RGC) tests for both shoot and root applications indicated an increase in root length and some increases in root number when applied as a root drench. This study indicates that root application of SWC improved seedling quality and increased the ability of seedlings to survive transplanting into pots.

Effect of Container Size and Shape on the Growth of Northern Red Oak Seedlings

Abstract Northern red oak (Quercus rubra L.) seedlings were grown in six container configurations differing in diameter, length, and volume. More shoot and lateral root dry weight was produced in a cylindrical polyvinylchloride (PVC) container 15.4 × 36 cm containing 6333 cm3 of potting medium than in containers with less medium volume. Seedling growth did not increase in a 15.4 × 110 cm container even though the potting medium volume was increased. Of all container variables measured, the ratio of potting medium surface area to potting medium depth (SA:D) showed the best correlation to seedling dry weight accumulation. Water or nutrient deficiencies could not be eliminated as factors contributing to differences in seedling growth.