Utilization of Tomato Landraces to Improve Seedling Performance under Salt Stress

Salt stress is considered as one of the most frequent factors limiting plant growth and productivity of crops worldwide. The aim of the study was to evaluate physiological and biochemical responses of nine diverse tomato genotypes exposed to salt stress. In this regard, four-week-old seedlings of one modern variety, five landraces, the salt-sensitive accession of ‘Ailsa Craig’, the salt-tolerant wild accession of S. pimpinellifolium ‘LA1579’, as well as the vitamin C-rich S. pennellii introgression line ‘IL12-4’, were exposed to moderate salt stress (200 mM NaCl) for 10 days. At the end of the stress treatment, agronomical traits and stress indices were evaluated, while gas exchange-related parameters, root electrolyte leakage, malondialdehyde content and ascorbic acid were also determined. All parameters were significantly affected by salt stress, but to a different extent, verifying the diverse degree of tolerance within the selected genotypes, and further highlighting the different stress-induced mechanisms. The landrace originated from ‘Santorini’ island, as well as the modern variety, which originated from traditional cultivars, demonstrated a better performance and adaptivity under moderate salt stress, accompanied by reduced lipid peroxidation and enhanced ascorbic acid content, indicating that they could be potential promising genetic material for breeding programs or as grafting rootstocks/scions.

Overwinter Storage of European Beech and Norway Spruce Planting Stock: Effect of Different Methods and Temperature Conditions

The aim of this research was to compare methods of overwinter storage of forest tree species planting stock and to specify of the optimal and the minimal temperature for freezing. Planting stock of European beech and Norway spruce were stored three times over a period of dormancy (2015/2016, 2016/2017, 2017/2018) (1) in freezers, (2) in an air-conditioned warehouse, (3) in a cave and (4) in soil (bare-rooted plants) and at a holding area (containerized plants), i.e., an open storage. During storage, the vitality of plants was determined using the root electrolyte leakage (REL) parameter, and in 2016 also by restoring growth in a sample of plants. The stored plants were always planted in a forest research plot in the spring and their basic morphological parameters and mortality were evaluated at the end of the growing season. The most suitable temperature for storage of both bare-rooted and containerized beech and spruce was in the range from −3.4 °C to −1.7 °C. The plants after overwinter storage showed no significant mortality after planting–they showed a high vitality of the fine roots and a normal increment, and were not damaged by frost, mold or other negative factors during storage.

Ascorbic acid of cowpea seeds under saline stress

Salinity adversely affects plant growth and metabolism by triggering increased production of reactive oxygen species (ROS). Ascorbic acid (AsA) is known to protect organelles and cells against ROS by preventing accumulation. The objective of this study was to study the effects of AsA on cowpea beans under saline stress. Cowpea seeds of the cultivars (BRS Marataoã and Setentão) were conditioned at concentrations of 0.0 (control); 0.25; 0.50; 0.75 and 1.00 mM AsA and seeded on paper towels, moistened at saline levels of 0.0 (control); 1.5; 3.0; 4.5; 6.0 and 7.5 dS.m-1, packed in a bench germinator at 25 °C. The statistical design adopted was a completely randomized 2 × 5 × 6 factorial design (cultivar x ascorbic acid x saline levels) with four replicates of 50 seeds per treatment. The analyzed variables were percentage of germination, first germination count, germination speed index, shoot and root length, total seedling dry weight, and leaf and root electrolyte leakage. Ascorbic acid at concentrations of 0.50 mM for BRS Marataoã and 0.75 mM for the Setentão, enabled the development of more vigorous seedlings and the reduction of membrane damage caused by oxidative stress both in the absence of salt and at the saline levels tested, including the highest one.

Change of cold hardiness in bare-rooted Norway spruce planting stock during autumn and its effect on survival

The objective of this study was to test a method of measurements of electrolyte leakage for determining an optimal autumn lifting date. The second objective was to obtain information about the effects of different autumn lifting dates on survival of Norway spruce (Picea abies [L.] Karst.) plants. A significant difference was found between lifting dates for the values of root electrolyte leakage (REL) from unstressed plants, but without clear tendency. The values of electrolyte leakage from shoots (SEL) were very stable (11–13%). On the other hand, the electrolyte leakage from roots (REL) decreased in dependence on different lifting date after artificial frost stress. On the first lifting date (end of September) the REL values were 77%. On the last lifting date (8 November) the REL values were 56%. The same tendency was found for SEL values (decrease from 63% at the end of September to 17% on 8 November). Differences were also found in the survival of plants. The plants lifted on earlier dates had nearly 100% mortality, which decreased with later date of lifting. The results of this study showed that cold hardiness of planting stock increased during autumn and was higher for shoots than for roots. The first results showed that it is possible to optimize the autumn lifting date of spruce planting stock by measurements of electrolyte leakage from shoots after artificial frost test.    

Desiccation Tolerance of Green Ash and Sugar Maple Fine Roots

Exposed fine roots are subject to desiccation, which may affect their survival as well as new root growth following bare root transplanting. Fine roots of dormant 1-year-old green ash (Fraxinus pennsylvanica) and sugar maple (Acer saccharum) seedlings, subjected to desiccation treatments of 0, 1, 2, or 3 hours in December and March, lost up to 82 percent of their water. Root electrolyte leakage, a measure of cell damage, tripled after three hours of desiccation. The increase was moderately, but significantly, greater in March for both species. Desiccation treatments had no effect on fine root survival. Growth of new roots (RGP) was also unaffected by desiccation treatments. RGP of maple was greater in March than December, but not ash.

The physiological responses of oak seedlings to warm storage

The effects of warm storage (15 °C) on the physiological responses and subsequent field performance of 2-year-old oak (Quercus robur L.) seedlings that had been cold (1–2 °C) stored until May were assessed. Shoot xylem pressure potential, shoot water content, shoot tip dry mass, root electrolyte leakage, and root growth potential were evaluated at regular intervals during the 21-day warm storage period. The date of lifting to cold storage had little effect on the physiological responses to warm storage. Root electrolyte leakage increased after 7 days of storage, despite the fact that root growth potential and survival were unaffected. Values then increased further before decreasing again by the end of the 21-day storage period to values similar to those recorded after 0 or 7 days of storage. Storage for up to 21 days greatly reduced root growth potential and shoot quality after planting in the field. The shoot xylem pressure potential of seedlings declined during the early stage of warm storage, but then increased to values similar to those recorded after cold storage. Shoot water content increased during the early storage period, then declined slightly, but values were higher after 21 days of storage than at the time of placement in warm storage. While most physiological responses fluctuated in a consistent manner, these changes were not necessarily predictable. Root growth potential was a good indicator of plant field performance potential, but the other physiological parameters were less useful to this end.

Seed lot, nursery, and bud dormancy effects on root electrolyte leakage of Douglas-fir (Pseudotsuga menziesii) seedlings

The effects of seed lot, nursery culture, and seedling bud dormancy status on root electrolyte leakage (REL) of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings were assessed to determine if these factors should be considered when interpreting REL for seedling quality. The relationships of REL to survival, net photosynthesis (Pn), stomatal conductance (gwv), mid-day shoot water potential (Ψmid), root growth capacity (RGC), and relative height growth were determined for each factor. Nursery culture had no effect on the relationship between REL and all other measured attributes. Seed lot affected the relationship between REL and Pn, Ψmid, and survival. However, critical REL (i.e., lowest value associated with detectable root damage) and PS80 REL (i.e., level associated with an 80% probability for survival) were similar between seed lots. Bud dormancy status affected the relationship between REL and survival, RGC, and relative height growth. Control levels of REL, critical REL, and PS80 REL decreased as the number of days required for 50% terminal bud break declined. Thus, terminal bud dormancy status must be known before REL can be used to assess seedling quality. If the bud dormancy status of Douglas-fir populations is known, then critical and PS80 REL levels may be useful as indices of root damage.

Seasonal Cold-acclimation Patterns of Sedum spectabile × telephium L. `Autumn Joy' and Sedum spectabile Boreau. `Brilliant'

Electrolyte leakage and regrowth were measured from September through January to determine cold hardiness of Sedum spectabile × telephium L. `Autumn Joy' and Sedum spectabile Boreau. `Brilliant' plants grown outdoors in central Iowa. Crowns were subjected to 0, –3, –6, –9, –12, –15, –18, –21, –24, or –27C. Regrowth tests were performed on whole crowns and electrolyte leakage was determined on excised tuberous root and crown tissue. Both cultivars were killed at –3C in September, but they acclimated gradually through January. Maximum hardiness was achieved in January, with killing temperatures of –27C for `Autumn Joy' and –21C for `Brilliant'. Regrowth quality ratings were significantly correlated with crown and tuberous root electrolyte leakage measurements, although the relationship was stronger for `Autumn Joy'.

Tolerance of conifer fine roots to cold storage

Fine-root electrolyte leakage from 2-year-old planting stock of three conifer species was measured on 13 dates between October 1989 and April 1990. The three species (Piceasitchensis (Bong.) Carr., Pseudotsugamenziesii (Mirb.) Franco, and Larixleptolepis (Sieb. & Zucc.) Gord.) were raised using either transplanting or undercutting and wrenching regimes. On each lifting date, excised fine roots were stored at 1 °C for 30 and 90 days. The deterioration of the fine roots was assessed by comparing electrolyte leakage values before and after storage. As the lifting date progressed from October to mid-December all three species became less adversely affected by storage, indicating that roots undergo physiological changes that increase their tolerance to prolonged cold storage. The interaction between lifting date and storage duration on fine-root quality differed in the three species. For example, Piceasitchensis could tolerate 90 days' storage commencing at any time from mid-December till early April with negligible root damage. Pseudotsugamenziesii could not tolerate 90 days' storage at any time of year, and tolerance to 30 days' storage was limited and could be substantially reversed. Fine roots of Larixleptolepis were only slightly damaged after 90 days' storage beginning from mid-November to the end of December.