Implications of ectomycorrhizal inoculation for drought stress tolerance of Atlas cedar (Cedrus atlantica (Endl.) Carrière) seedlings

Background: Ectomycorrhizal inoculation is a promising strategy to minimise the initial transplant shock and increase plant survival and growth during the first years of out-planting in the field. The aim of this research was to investigate the effect of sporal inoculum of three ectomycorrhizal fungi: Cortinarius cedretorum, Amanita vaginata and Inocybe geophylla on tolerance levels of Atlas cedar (Cedrus atlantica (Endl.) Carrière) seedlings subjected to applied drought stress in nursery conditions. Methods: Carpophores, seeds and organic forest soil were collected under pure stands of Atlas cedar. After fifteen months of growth, seedlings were subjected to drought stress by withholding water for thirty days; we assessed morphological and physiological variables of all seedling batches (inoculated and uninoculated, controlled and stressed seedlings) Results: All roots of inoculated stressed seedlings were mycorrhizal. The mycorrhization rates were 67%, 64.6% and 53.6% for stressed seedlings inoculated with Cortinarius cedretorum, Amanita vaginata, Inocybe geophylla, respectively. This root mycorrhization was accompanied by a significant improvement in seedling growth, especially height and length of the main root (10.2 cm, 52 cm) reached in stressed seedlings inoculated with Cortinarius cedretorum. There was a significant increase in relative water content, total chlorophyll, carotenoids, soluble sugars and starch, superoxide dismutase and ascorbate peroxydase enzyme activities in inoculated stressed seedlings compared with uninoculated seedlings. Conclusions: Inoculation of Atlas cedar seedlings with spores of ectomycorrhizal fungi remains a very effective alternative for improving growth and the morphological and physiological status of seedlings under drought conditions. Cortinarius cedretorum appears to be consistently advantageous followed by Amanita vaginata and Inocybe geophylla.

Effect of Rhizophagus irregularis on Growth and Quality of Cannabis sativa Seedlings

Rhizophagus irregularis is an arbuscular mycorrhiza fungus that can enhance plant nutrition and reduce transplant shock on seedlings. The present study aims to evaluate the effects of this fungus on the quality of cannabis (Cannabis sativa L.) seedlings. A greenhouse float system experiment was conducted in a completely randomized design with three treatments. The treatments included the application of 40, 80 and 120 fungus spores per L of nutrient solution (AMF1, AMF2 and AMF3, respectively). The evaluation was performed based on the agronomic characteristics of the seedlings (root and stem length and weight, stem diameter), N and P content, survival rate, and the Dickson’s quality index (DQI). Results indicated that root length and stem dry weight were significantly increased (by 34.14% and 21.4%, respectively) in the AMF3 treatment. The biomass of the seedlings’ roots, the fresh weight and the N content were not affected by the AMF. On the contrary, survival rate, P content and DQI were significantly increased in AMF3 (by 5%, 24.3% and 12.4% respectively). Overall, our findings suggest that the application of high doses of Rhizophagus irregularis (AMF3) on float system-produced cannabis seedlings results in a considerable increment of their quality.

Humic Substances Improve Vegetable Seedling Quality and Post-Transplant Yield Performance under Stress Conditions

Vegetable growers require vigorous transplants in order to reduce the period of transplant shock during early stand establishment. Organic media containing solid humic substances (HS) are amendments that have not been comprehensively explored for applications in containerized vegetable transplant production systems. In this study, HS (1% v/v) were applied to a peat-based growth medium to evaluate pre- and post-transplant growth modulation of four economically important vegetable species. Those were: pepper, tomato, watermelon, and lettuce. Seeding for all species was performed in two periods in order to evaluate their post-transplant yield performance under drought (water deficit vs. well-watered) and heat (hot vs. cool season) stresses. Compared with control, HS-treated plants had: (1) increased leaf and root biomass after transplanting due to faster growth rates; (2) lower root/shoot ratio before transplanting, but higher after 10 days of field establishment; and (3) increased root length and surface area. The negative effects of heat and drought stresses on crop yield were more prominent in control plants, while HS-treated transplants were able to mitigate yield decreases. The results clearly demonstrated the benefits of using solid HS as a management input to improve transplant quality in these crop species.

Preplant Application of 1-Methylcyclopropene Improves Postplanting Performance of Tomato Transplants by Suppressing Ethylene-induced Stress Responses

Transplant shock is caused by various types of abiotic stress, limiting stand establishment and productivity of many vegetable crops. Although postplanting stress can be minimized under well-managed field conditions, mechanical stress is unavoidable during the transport and transplanting of seedlings. Mechanical stress stimulates ethylene production, which in turn, induces overall growth retardation as a stress adaptation strategy. We hypothesized that, under optimum field conditions, transplant shock is caused primarily by ethylene-induced stress responses, and that inhibiting ethylene action can reduce transplant shock by maintaining uninterrupted growth. In this study, a new spray formulation of 1-methylcyclopropene (1-MCP) was used to inhibit ethylene perception in tomato (Solanum lycopersicum L.) seedlings. A bioassay experiment demonstrated reduced ethylene sensitivity in 1-MCP–treated (1 mg·L−1) seedlings using leaf epinasty and chlorosis as measured responses. Field experiments evaluated growth, physiological, and yield responses to preplant spray treatment of 1-MCP (12.5–50 mg·L−1) under optimum field conditions. Postplanting growth modulation by 1-MCP at the flowering stage was characterized by enhanced height growth and suppressed stem diameter growth, indicating the inhibition of ethylene-induced stress responses. At the fruit harvest stage, preplant 1-MCP treatment increased shoot biomass by 23% and flower production by 22%, while improving photosynthetic capacity on a whole-plant basis. As a result, 1-MCP–treated plants produced 13% to 24% higher total marketable fruit yields than untreated plants in two consecutive growing seasons. Correlation analyses revealed that flower number increased proportionally to shoot biomass, and marketable fruit number increased proportionally to flower number. These results support our hypothesis and propose that preplant 1-MCP treatment is a new stress-management approach to reducing transplant shock. Importantly, this new technique is easily implementable by commercial transplant nurseries with no negative side effect on transplant quality and fruit development.

Transplanting the Soul-Tree: An Analytical Perspective on how the Sesame Approach and Movement with Touch and Sound Became the Fertile Soil for the Psychological Support and Therapy for Refugee Women

This case study explores how the Sesame approach and specifically Marian Lindkvist's ‘Movement with Touch and Sound’ (MTS) became the fertile soil for the psychological support and healing of refugee women in an innovative community centre in Athens. Expression through movement, ritual, imagination and play created the fine line of working obliquely yet deeply with severely traumatised women, most of whom were survivors of gender-based violence (GBV). The archetypal image of the tree, which develops new roots after the so called ‘transplant shock’, is a guiding metaphor that emerged through the therapeutic process and held an enormous significance as a representative unconscious image of the women's inner and outer journey of transformation.

Landscape Establishment for Baldcypress, Red Maple, and Chaste tree is Delayed for Trees Transplanted from Larger Containers1

With container-grown trees offered to the public in an increasing array of sizes, it is important to determine the effects of different sizes of container stock on transplant establishment. Clonal replicates of Vitex agnus-castus, Acer rubrum var. drummondii, and Taxodium distichum grown under common nursery conditions in five container sizes, 3.5, 11.7, 23.3, 97.8, or 175.0 L (#1, #3, #7, #25, or #45, respectively), were transplanted to a sandy clay loam field. Physiological stress was measured using xylem water potential and photosynthetic gas exchange rates. Height, trunk diameter, and canopy spread were monitored post-transplant for three growing seasons and root growth was sampled for the first two growing seasons. Trees of all three species from smaller-sized containers, 23.3 L (#7) or less, exhibited reduced transplant shock, decreased establishment time and increased growth rates in comparison to larger-sized containers, apart from increased mortality in 3.5 L (#1) A. rubrum and slower growth in 3.5 L (#1) T. distichum compared to those transplanted from 11.7 L (#3) or 23.3 L (#7) containers Reduced stress levels and increased growth rates corresponded in timing with greater change in root extension of smaller container-grown trees. At the end of three growing seasons, no statistical differences in height or trunk diameter were present for V. agnus-castus container sizes. With a modest wait, consumers may find that smaller container-grown trees will overcome transplant stress more quickly and exhibit growth rates that surpass those of larger container-grown trees. Index words: Acer rubrum, Taxodium distichum, Vitex agnus-castus, container-grown trees, transplant shock, transplant establishment, photosynthesis, transpiration, water stress. Species used in this study: Chaste tree (Vitex agnus-castus L. [an unnamed white flowering clone]); red maple (Acer rubrum L. var. dummondii [Hook. & Arn. ex Nutt.] Sarg. ‘Maroon'); bald cypress (Taxodium distichum (L.) Rich. [test clone TX8DD38]).

Fine Root Hydraulic Conductance Is Related to Post-transplant Recovery of Two Quercus Tree Species

In our study, we investigated whether root hydraulic conductance is related to post-transplant recovery. We used two Quercus species that differ in their transplant ability, Q. bicolor and Q. macrocarpa. Q. bicolor easily survives transplanting, whereas Q. macrocarpa often does not. We compared root hydraulic conductance after transplanting between control (without root pruning) and root-pruned, 1-year-old, small-caliper trees. We also examined the effects of transplant timing on post-transplant recovery of large-caliper trees. Hydraulic conductance in fine roots was correlated with recovery of the two Quercus species after transplanting. Six months after transplanting, small-caliper Q. bicolor trees had similar specific hydraulic conductance (KS) in fine roots compared with the KS before root-pruning, whereas fine root KS in small-caliper Q. macrocarpa trees decreased. Lower pre-dawn and midday xylem water potential in root-pruned Q. macrocarpa 6 weeks after transplanting indicates that root-pruned Q. macrocarpa experienced transplanting-induced water stress. For large-caliper trees, all Q. macrocarpa trees exhibited typical symptoms of transplant shock regardless of transplant timing, which was the result of higher vulnerability to mild water stress compared with Q. bicolor, resulting in a large reduction in fine root KS. Fine root KS in spring-transplanted Q. bicolor trees was much higher than that in fall-transplanted trees, implying spring transplanting is optimal for Q. bicolor. Other intrinsic characteristics of the species should be considered in the future when making better decisions on transplant timing such as xylem anatomy, carbon storage, rhizosphere conditions, and plant growth.

The effect of plant growth-promoting rhizobacteria on asparagus seedlings and germinating seeds subjected to water stress under greenhouse conditions

Plant growth-promoting rhizobacteria (PGPR) can have positive effects on vigour and productivity, especially under stress conditions. In asparagus ( Asparagus officinalis L.) field culture, seeds are planted in high-density nurseries, and 1-year-old crowns are transplanted to production fields. Performance can be negatively affected by water stress, transplant shock, and disease pressure on wounded roots. PGPR inoculation has the potential to alleviate some of the stresses incurred in the production system. In this study, the effects of PGPR ( Pseudomonas spp.) treatment were determined on 3-week-old greenhouse-grown seedlings and germinating seeds of 2 asparagus cultivars. The pots were irrigated to a predetermined level that resulted in optimum growth or the plants were subjected to drought or flooding stress for 8 weeks. The cultivars responded differently to PGPR: single inoculations of seedlings enhanced growth of ‘Guelph Millennium’ under optimum conditions and ‘Jersey Giant’ seedlings under drought stress. Seed inoculations with PGPR resulted in a positive response only for ‘Guelph Millennium’, for which both single or multiple inoculations enhanced plant growth under drought stress.

Tree Establishment: A Review of Some of the Factors Affecting Transplant Survival and Establishment

Transplant success and tree establishment depend on a chain of events from propagation, to production, to harvest, to shipping, to maintenance on the job site, to transplanting techniques, to aftercare. Failure to follow proper practices at any step in this sequence will compromise transplant success and establishment. This article reviews some of the factors that induce transplant shock and slow establishment of transplanted nursery stock such as root and mineral nutrient loss, soil moisture stress and xylem vessel cavitation, and methods used to reduce transplant shock.