Scientia Horticulturae 

About: Scientia Horticulturae is an academic journal. The journal publishes majorly in the area(s): Shoot & Rootstock. It has an ISSN identifier of 0304-4238. Over the lifetime, 11824 publication(s) have been published receiving 259201 citation(s).

Salinity–mineral nutrient relations in horticultural crops

Abstract: The relations between salinity and mineral nutrition of horticultural crops are extremely complex and a complete understanding of the intricate interactions involved would require the input from a multidisciplinary team of scientists. This review addresses the nutrient elements individually and we emphasise research directed towards the organ, whole-plant and field level. We have attempted to synthesise the literature and reconcile results from experiments conducted in a variety of conditions such as soil and solution cultures, those using mixed and single-salt (only NaCl) compositions, and those conducted over short (days) and long periods (months) of time. Crop performance may be adversely affected by salinity-induced nutritional disorders. These disorders may result from the effect of salinity on nutrient availability, competitive uptake, transport or partitioning within the plant. For example, salinity reduces phosphate uptake and accumulation in crops grown in soils primarily by reducing phosphate availability but in solution cultures ion imbalances may primarily result from competitive interactions. Salinity dominated by Na+ salts not only reduces Ca2+ availability but reduces Ca2+ transport and mobility to growing regions of the plant, which affects the quality of both vegetative and reproductive organs. Salinity can directly affect nutrient uptake, such as Na+ reducing K+ uptake or by Cl- reducing NO3/- uptake. Salinity can also cause a combination of complex interactions that affect plant metabolism, susceptibility to injury or internal nutrient requirement. Despite a large number of studies that demonstrate that salinity reduces nutrient uptake and accumulation or affects nutrient partitioning within the plant, little evidence exists that adding nutrients at levels above those considered optimal in non-saline environments, improves crop yield. Nutrient additions, on the other hand, have been more successful in improving crop quality such as the correction of Na-induced Ca2+ deficiencies by supplemental calcium. Nutrient additions may also reduce the incidences of injury as has been observed in the reduction of Cl-toxicity symptoms in certain tree crops by nitrate applications. It is reasonable to believe that numerous salinity-nutrient interactions occur simultaneously but whether they ultimately affect crop yield or quality depends upon the salinity level and composition of salts, the crop species, the nutrient in question and a number of environmental factors.

Plant biostimulants: Definition, concept, main categories and regulation

Abstract: A plant biostimulant is any substance or microorganism applied to plants with the aim to enhance nutrition efficiency, abiotic stress tolerance and/or crop quality traits, regardless of its nutrients content. By extension, plant biostimulants also designate commercial products containing mixtures of such substances and/or microorganisms. The definition proposed by this article is supported by arguments related to the scientific knowledge about the nature, modes of action and types of effects of biostimulants on crop and horticultural plants. Furthermore, the proposed definition aims at contributing to the acceptance of biostimulants by future regulations, especially in the EU, drawing the lines between biostimulants and fertilisers, pesticides or biocontrol agents. Many biostimulants improve nutrition and they do so regardless of their nutrients contents. Biofertilisers, which we propose as a subcategory of biostimulants, increase nutrient use efficiency and open new routes of nutrients acquisition by plants. In this sense, microbial biostimulants include mycorrhizal and non-mycorrhizal fungi, bacterial endosymbionts (like Rhizobium) and Plant Growth-Promoting Rhizobacteria. Thus, microorganisms applied to plants can have a dual function of biocontrol agent and of biostimulant, and the claimed agricultural effect will be instrumental in their regulatory categorization. The present review gives an overview of the definition and concept of plant biostimulants, as well as the main categories. This paper will also briefly describe the legal and regulatory status of biostimulants, with a focus on the EU and the US, and outlines the drivers, opportunities and challenges of their market development.

Tolerance of vegetable crops to salinity

Abstract: Global constraints on fresh water supplies and the need to dispose of agricultural, municipal, and industrial waste waters have intensified interest in water reuse options. In many instances, the value of the water is decreased solely because of its higher salt concentration. Although quantitative information on crop salt tolerance exists for over 130 crop species, there are many vegetables which lack definitive data. Vegetable crops are defined as herbaceous species grown for human consumption in which the edible portions consist of leaves, roots, hypocotyls, stems, petioles, and flower buds. The salt tolerance of vegetable species is important because the cash value of vegetables is usually high compared to field crops. In this review some general information is presented on how salinity affects plant growth and development and how different measurements of salinity in solution cultures, sand cultures, and field studies can be reconciled to a common basis. The salt tolerance of vegetables has been condensed and reported in a uniform format based on the best available data. Discrepancies and inconsistencies exist in some of the information due to differences in cultivars, environments, and experimental conditions. For a great number of species little or no useful information exists and there is an obvious need for research.

Tomato and salinity

Abstract: The effects of salinity on tomato plant growth and fruit production, the cultural techniques which can be applied to alleviate the deleterious effects of salt, and the possibilities of breeding salt-tolerant tomatoes are reviewed. Salinity reduces tomato seed germination and lengthens the time needed for germination to such an extent that the establishment of a competitive crop by direct seeding would be difficult in soils where the electrical conductivity (EC) of a saturated extract was equal to or above 8 dS m−1. Priming seeds primed with 1 M NaCl for 36 h seems advisable to establish a crop by direct sowing in saline soils, and seedling conditioning, either by exposure to moderately saline water exposure or by withholding watering until seedlings wilt for 20–24 h, can be recommended for crops that are to be established by transplanting. Yields are reduced when plants are grown with a nutrient solution of 2.5 dS m−1 or higher and above 3.0 dS m−1 an increase of 1 dS m−1 results in a yield reduction of about 9–10%. At low ECs, yield reduction is caused mainly by reduction in the average fruit weight, whilst the declining number of fruits explains the main portion of yield reduction at high ECs. Since the smaller the fruit, the less important the reduction in fruit weight caused by salt, small size tomatoes are recommended to be grown at moderate salinity. Short cycle crops, in which only 4–6 trusses are harvested, are also recommended – especially since upper inflorescences are particularly sensitive to salt. Root growth, which slows when salinity reaches 4–6 dS m−1, appears to be less affected by salt than shoot growth. Salinity raises Na+ concentration in roots and leaves of tomato plants. A higher Na+ concentration in the leaves lowers the osmotic potential and promotes water uptake, but it is the ability to regulate Na+ in older leaves while maintaining a low Na+ concentration in young leaves which seems to be related to salinity tolerance. Ca2+ and K+ concentrations in roots of salinised tomato plants change little under salinity whilst they are greatly reduced in leaves; those plants taking up more Ca2+ and K+ from the salinised medium will have lower Na+/K+ and Na+/Ca2+ ratios and an equilibrium of nutrients more similar to the non-salinised plants. Increasing Ca2+ and K+ concentrations in the nutrient solution is, consequently, advisable. Root NO−3 concentration is maintained for longer periods after salinisation or under higher salinity levels than leaf NO−3 concentration. Salinity enhances tomato fruit taste by increasing both sugars and acids, fruit shelf life and firmness are unchanged or slightly lowered, but the incidence of blossom end rot is much higher. Breeding of tomato cultivars tolerant to moderate salinity will only occur after pyramiding in a single genotype several characteristics such as greater root volume, higher efficiency in water absorption and dry matter formation per unit of water absorbed, higher selectivity in absorption of nutrients, and higher capability to accumulate toxic ions in vacuoles and old leaves.