Maize is grown under a wide spectrum of soil and climatic conditions. Maize is moderately sensitive to salt stress; therefore, soil salinity is a serious threat to its production worldwide. Understanding maize response to salt stress and resistance mechanisms and overviewing management options may help to devise strategies for improved maize performance in saline environments. Here, we reviewed the effects, resistance mechanisms, and management of salt stress in maize. Our main conclusions are as follows: (1) germination and stand establishment are more sensitive to salt stress than later developmental stages. (2) High rhizosphere sodium and chloride decrease plant uptake of nitrogen, potassium, calcium, magnesium, and iron. (3) Reduced grain weight and number are responsible for low grain yield in maize under salt stress. Sink limitations and reduced acid invertase activity in developing grains is responsible for poor kernel setting under salt stress. (4) Exclusion of excessive sodium or its compartmentation into vacuoles is an important adaptive strategy for maize under salt stress. (5) Apoplastic acidification, required for cell wall extensibility, is an important indicator of salt resistance, but not essential for better maize growth under salt stress. (6) Upregulation of antioxidant defense genes and β-expansin proteins is important for salt resistance in maize. (7) Arbuscular mycorrhizal fungi improve salt resistance in maize due to better plant nutrient availability. (8) Seed priming is an effective approach for improving maize germination under salt stress. (9) Integration of screening, breeding and ion homeostasis mechanisms into a functional paradigm for the whole plant may help to enhance salt resistance in maize.

/pdf/salt-stress-in-maize-effects-resistance-mechanisms-and-3cbt0nnpsc.pdf

Salt stress in maize: effects, resistance mechanisms, and management. A review

Plant growth promoting bacteria as an alternative strategy for salt tolerance in plants: A review.

Plant hormones regulate plant growth and development by affecting an array of cellular, physiological, and developmental processes, including, but not limited to, cell division and elongation, stomatal regulation, photosynthesis, transpiration, ion uptake and transport, initiation of leaf, flower and fruit development, and senescence. Environmental factors such as salinity, drought, and extreme temperatures may cause a reduction in plant growth and productivity by altering the endogenous levels of plant hormones, sensitivity to plant hormones, and/or signaling pathways. Molecular and physiological studies have determined that plant hormones and abiotic stresses have interactive effects on a number of basic biochemical and physiological processes, leading to reduced plant growth and development. Various strategies have been considered or employed to maximize plant growth and productivity under environmental stresses such as salt-stress. A fundamental approach is to develop salt-tolerant plants through gene...

The Physiological, Biochemical and Molecular Roles of Brassinosteroids and Salicylic Acid in Plant Processes and Salt Tolerance

Tomorrow’s agriculture, challenged by increasing global demand for food, scarcity of arable lands, and resources alongside multiple environment pressures, needs to be managed smartly through sustainable and eco-efficient approaches. Modern agriculture has to be more productive, sustainable and environmentally friendly. While macronutrients such as nitrogen (N), phosphorus (P), potassium (K) and sulfur (S) supplied by mineral fertilizers are vital to crop production, agriculturally beneficial microorganisms may also contribute directly (i.e. biological N2 fixation, P solubilization, phytohormone production, etc.) or indirectly (i.e. antimicrobial compounds biosynthesis, elicitation of induced systemic resistance, etc.) to crop improvement and fertilizers efficiency. Microbial-based bioformulations that increase plant performance are greatly needed, and in particular bioformulations that exhibit complementary and synergistic effects with mineral fertilization. Such an integrated soil fertility management strategy has been demonstrated through several controlled and non-controlled experiments, but more efforts have to be made in order to thoroughly understand the multiple functions of beneficial microbes’ functions within the soil microbial community itself and in interaction with plants and mineral resources. In fact, the combined usage of microbial (i.e. beneficial microorganisms: N2-fixing (NF), P-solubilizing and P mobilizing, etc.) and mineral resources is an emerging research area that aims to design and develop efficient microbial formulations which are highly compatible with mineral inputs, with positive impacts on both crops and environment. This novel approach is likely to be of a global interest, especially in most N- and P-deficient agro-ecosystems. In this review, we report on the importance of NF bacteria and P solubilizing/mobilizing microbes as well as their interactions with mineral P fertilization in improving crop productivity and fertilizers efficiency. In addition, we shed light on the interactive and synergistic effects that may occur within multi-trophic interactions involving those two microbial groups and positive consequences on plant mineral uptake, crop productivity and resiliency to environmental constraints. Improving use of mineral nutrients is a must to securing higher yield and productivity in a sustainable manner, therefore continuously designing, developing and testing innovative integrated plant nutrient management systems based on relevant biological resources (crops and microorganisms) is highly required.

/pdf/soil-microbial-resources-for-improving-fertilizers-bxffll7j90.pdf

Soil Microbial Resources for Improving Fertilizers Efficiency in an Integrated Plant Nutrient Management System

contributed by a variety of authors in which different strategies for insect control are discussed. All the content is contributed by authors from the USA, with the exception of a chapter on enhancing insect resitance in rice written by authors from the International Rice Research Institute, and a chapter on Bt crystal proteins by Marnix Peferoen, whose competent contribution certainly does not suggest that he was included as a “token European”! The emphasis on American authors (and research) gives this book a rather onesided feel, although many of the individual chapters do take a more wide-ranging view. Inevitably, the volume is a little selective, even as a survey of research in the USA; for example, although the possible role of peroxidases in plant defence against insects is discussed at length, other oxidative enzymes that are equally likely to play a role in defence, such as lipoxygenases and polyphenol oxidases, are not mentioned. The volume is built around three chapters on the use of Bt toxins for insect control, which is entirely appropriate given the widespread use of their encoding genes, with applications in transgenic maize and potatoes described in detail. However, alternatives to the expression of Bt toxins in transgenic plants, such as the introduction of genes encoding foreign protease inhibitors, amylase inhibitors, lectins, cholesterol oxidase, and chitinases are given full coverage, as are some less well-developed areas such as manipulation of secondary metabolism. There are also good chapters on the more applied aspects of using transgenics, such as managing engineered resistance. Inevitably, some chapters are better than others, but the standard is generally good, and no chapter is unworthy of inclusion. The volume as a whole is very well produced, and the quality of the figures is high; however, the index is not wholly accurate, although it is quite thorough. All in all, this is a volume that can be confidently recommended as a sound purchase for libraries, and for individual researchers with interest in the subject area.

Introduction to Plant Physiology. Edited by W.G. Hopkins

The effects of indoleacetic acid (IAA) and inorganic nutrients (K and P) on some physiological parameters and kernel yield of maize (Zea mays L.) cultivar DK 647 F1 were investigated in two parallel experiments conducted in the same growth season in a saline field. Sodium chloride equivalent to 100 mM was added to the irrigation water and saline water applied to the field using a drip irrigation system. Indoleacetic acid was applied as foliar spray. Potassium and P were applied to the soil at the sowing time as monopotassium phosphate at 200 kg ha -1 . Salinity significantly reduced shoot dry mass, cob yield, total kernel yield, weight of 1000 kernels, chlorophylls “a” and “b” and relative water content in the maize plants, but increased proline accumulation, activities of the key antioxidant enzymes superoxide dismutase (SOD; EC 1.15.1.1), peroxidase (POD; EC. 1.11.1.7), catalase (CAT; EC. 1.11.1.6) and polyphenol oxidase (PPO; 1.10.3.1), and electrolyte leakage. However, application of K and P or foliar spray of IAA mitigated the adverse effects of salinity on maize plants. The most promising effect of IAA or K and P on alleviation of salt stress on maize was found when they were applied in combination. Leaf sodium (Na + ) concentration increased substantially, but leaf K + , Ca 2+ and P concentrations decreased markedly in the salt stressed maize plants. However, exogenous application of nutrients, IAA, or their combination considerably reduced Na + concentration and significantly improved K + , Ca 2+ , and P levels in the salt stressed maize plants. The exogenously applied inorganic nutrient- or auxin-induced growth promotion in maize plants was found to be associated with increased photosynthetic pigment concentration and leaf Na + /K + ratio, reduced membrane permeability, and altered activities of

/pdf/alleviation-of-salt-stress-induced-adverse-effects-on-maize-3m9pz8jwym.pdf

Alleviation of salt stress-induced adverse effects on maize plants by exogenous application of indoleacetic acid (IAA) and inorganic nutrients - A field trial

This study examined the effects of kinetin (KIN) and indoleacetic acid (IAA) sprayed on the leaves of salinity- stressed maize (Zea mays L. cv., DK 647 F1) plants grown in field conditions. Salt stress was created by adding 100 mM NaCl to the irrigation water through a drip irrigation system during the irrigation schedule. Kinetin (KIN), indole acetic acid (IAA), and their combinations were sprayed foliarly. Salt stress (S) reduced the total dry matter, grain yield, chlorophyll content, and relative water content (RWC), but increased electrolyte leakage and proline accumulation in the maize plants. Foliar applications of both KIN and IAA treatments overcame to variable extents the adverse effects of NaCl stress on the earlier mentioned physiological parameters. However, the combination of KIN plus IAA did not improve salinity tolerance in maize plants. Salt stress increased Na + concentration, and reduced those of Ca 2+ and K + in the leaves of maize plants. Foliar application of both KIN and IAA significantly reduced Na + concentration and increased those of Ca 2+ and K + . Foliar application of KIN and IAA, especially at 2 mM, counteracted some of the salt induced adverse effects by enhancing essential inorganic nutrients as well as by maintaining membrane permeability.

/pdf/effect-of-foliar-applied-kinetin-and-indole-acetic-acid-on-1sobfqgpz6.pdf

Effect of foliar applied kinetin and indole acetic acid on maize plants grown under saline conditions

Salicylic acid, 5-Sulfo Salicylic acid and Acetylsalicylic acid are Salicylic acid derivatives. They differ in their substitution on the benzene ring and may have different effects on plant membranes. The effects of the derivatives of various Salicylic Acid [Salicylic acid (SA), 5-Sulfo Salicylic Acid (SSA) and Acetylsalicylic Acid (ASA)] on antioxidant enzyme activities, mineral element uptake, growth and some stress related parameters of maize (Zea mays L. cv. DK 684) plant grown in containers under salinity stress were investigated. Salicylic acid were applied by foliar treatments at five days interval. Treatments were: 1-) control, 2-) salt treatment 125 mM NaCl, 3-)125 mM NaCl + 1 mM Salicylic Acid, 4-)125 mM NaCl + 1 mM Sulfo Salicylic Acid, 5)125 mM NaCl + 1 mM Acetylsalicylic Acid, 6-) 125 mM NaCl + 2 mM Salicylic Acid, 7-)125 mM NaCl + 2 mM Sulfo Salicylic Acid and 8-) 125 mM NaCl + 2 mM Acetylsalicylic Acid. Salt treatment reduced the plant growth, chlorophyll content, relative water content and ear of corn weight, but increased antioxidative enzymes and membrane permeability. Besides compared with the control group, nutrient uptakes of leaves and roots were inhibited by salt treatment. Tested parameters were generally positively affected by the applications of the salicylic acid derivatives compared to the salt treatment. For example, total chlorophyll, shoot dry matter, relative water content and ear of corn weight were ameliorated by 1 and 2 mM SSA, 1 mM ASA and 1 mM SSA treatments. The macro and micro element content of leaves and roots were generally increased by salicylic acid treatments compared to the salt treatment. Salicylic acid application seems to be more effective in the element uptakes than other ones. Salicylic acid treatments decreased antioxidant enzyme activities compared to the salt treatment. The data clearly shows that, the various derivatives of salicylic acid could protect maize plant from the detrimental effects of salt stress by improving physiological parameters tested such as relative water content, membrane permeability and nutrient status of plant.

Comparative effects of various salicylic acid derivatives on key growth parameters and some enzyme activities in salinity stressed maize (Zea mays L.) plants

This study was aimed to examine the effects of seaweed extract (SW) and humic acid on the fruit yield, dry weight (DW%), protein, proline, lipid peroxidation (LPO) and antioxidative enzyme activity of pepper plants (Capsicum annuum L.) grown under saline conditions (100 mM). The obtained results indicated that salinity stress affected deleteriously plant growth and all other parameters. Besides, the treatment of seaweed (SW) and humic acid (HA) improved vegetative growth in the plant at all concentration levels applied under salinity conditions. Leaf fresh and dry weight was increased by all SW and HA applications in salinity stressed plant compared to those of control. Furthermore, there was a significant improvement in antioxidant enzyme activity, such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) activities in the plant under salt stress and treated with SW and HA compounds. It suggests that seaweed and humic acid can enhance salt stress tolerance and leads to conservation of pepper plant against oxidative stress.

/pdf/physiological-effects-of-the-brown-seaweed-ascophyllum-56kems73rw.pdf

Physiological effects of the brown seaweed Ascophyllum nodosum) and humic substances on plant growth, enzyme activities of certain pepper plants grown under salt stress.

A glasshouse study was conducted to examine the ameliorative effects of exogenously applied nitric oxide (NO) on salinity-induced oxidative defense mechanisms and some vital metabolic attributes in two maize cultivars differing in salinity tolerance. It also aimed to compare the effects of two different modes of NO application on different parameters of plants grown under a saline regime. Two maize cultivars, namely DK 5783 (salt-tolerant) and Apex 836 (salt-sensitive), were subjected to saline stress, and two levels of NO were applied as presowing or foliage spray. Saline stress caused significant suppression in total fresh and dry biomass, maximum fluorescence yield (Fv/Fm), leaf water potential, and total chlorophylls (a + b) in the plants of both maize cultivars. On the other hand, it increased leaf osmotic pressure, proline accumulation, hydrogen peroxide (H2O2) and malondialdehyde (MDA) concentrations, membrane permeability, and the activities of some key antioxidant enzymes, peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT). Exogenously applied NO in both modes partly alleviated the adverse effects of salinity on plants of both maize cultivars. In most cases there seemed to be no difference between seed and foliar application of NO in alleviating the adverse effects of salt stress on maize plants. NO partially improved salt tolerance of maize plants; it reduced Na+ but increased N, K+, Ca2+, and P in the maize plants under saline regimes. The NO treatment conferred enhanced tolerance to salinity by reducing MDA and H2O2 levels and antioxidant enzymes such as SOD, CAT, and POD, as well as enhancing photosynthetic pigments under salinity stress.

/pdf/exogenously-applied-nitric-oxide-confers-tolerance-to-1l5ylob664.pdf

Exogenously applied nitric oxide confers tolerance to salinity-induced oxidativestress in two maize (Zea mays L.) cultivars differing in salinity tolerance

Atilla Levent Tuna

Papers

Alleviation of salt stress-induced adverse effects on maize plants by exogenous application of indoleacetic acid (IAA) and inorganic nutrients - A field trial

Effect of foliar applied kinetin and indole acetic acid on maize plants grown under saline conditions

Comparative effects of various salicylic acid derivatives on key growth parameters and some enzyme activities in salinity stressed maize (Zea mays L.) plants

Physiological effects of the brown seaweed Ascophyllum nodosum) and humic substances on plant growth, enzyme activities of certain pepper plants grown under salt stress.

Exogenously applied nitric oxide confers tolerance to salinity-induced oxidativestress in two maize (Zea mays L.) cultivars differing in salinity tolerance