Antioxidant System in Citrus Under Nutrient Stress Conditions: Latest Developments

Abstract

Natural distribution of mineral nutrients in the earth crust is a crucial factor that determines the distribution of plant species favoring the spreading of species with speci fi c adaptations to nutrient de fi ciency or excess. Throughout years, humans have learned how to provide nutrients to poorly fertilized soils and, to some extent, how to regulate absorption of certain nutrients when these are present in excess in the substrate. However, this has led also to an overfertilization of certain areas therefore contaminating arable soils and aquifers. In plants, both excess and de fi cient fertilization induce alterations in metabolism growth and reproductive development. The extent to which the nutrient imbalance affects plant physiology depends on the speci fi c nutrient and the relative tolerance of the plant species. In addition, nutrients might also interact with each other, depending on their relative concentration, leading to nonexpected alterations in plants. For these reasons, nutrient imbalances are considered a source of abiotic stress in crop plants. As for other abiotic stress conditions such as salinity, soil waterlogging, heat, plants respond by modulating their photosynthetic metabolism and subsequently overproducing highly reactive oxidative subproducts as a secondary source of stress. In this sense, some of the macroscopic effects observed in plants subjected to nutritional imbalances (e.g., necrotic spots, chlorosis) could be a direct (or indirect) result of the production and accumulation of these substances. In this chapter, the effects of nutritional imbalances on oxidative stress are reviewed, focusing on citrus and providing examples on other crops or Arabidopsis thaliana . AbstractNutritional imbalances are important factors that determine the distribution of natural populations of plants. However, in crop plants, alterations in nutrient levels limit vegetative growth, development and ultimately affect yield and production quality. In citrus, this is a relevant aspect due to the economic importance of this fruit tree. As other abiotic stress factors, nutrient imbalances affect the redox state of the cells by altering normal electron fl ow through transport chains (chloroplastic and/or mitochondrial) or impairing reactive oxygen species scavenging ability of plants. In this chapter, the effects of macro-and micronutrient imbalances on citrus cell redox state are reviewed, paying special attention to the defense and detoxi fi cation mechanisms involved. In addition, the role of reactive oxygen species as signaling compounds alone or associated with plant hormones is discussed.

Proteomic Analyses Provide Novel Insights into Plant Growth and Ginsenoside Biosynthesis in Forest Cultivated Panax ginseng (F. Ginseng)

“…ROS scavenging enzymes such as peroxiredoxin (spot 18) (Figure 4 clusters D), SOD (Figure 7G ), CAT (Figure 7H ), and Grx gene (Figures 8A,B ; Ding et al, 2010 ) were up-regulated in the early growth stage and down-regulated in the mature stage. Thus, F. Ginseng activated the antioxidant defense system to cope with the oxidative stress by maintaining a relatively stable level of ROS (Arbona and Gómez-Cadenas, 2012 ).…”

Oxidant and antioxidant compounds, gas exchange and growth of young Schizolobium parahyba var. amazonicum plants under high boron and calcium concentrations

“…To EL, increases were caused by the H 2 O 2 accumulation; however this negative effect was more evident in the roots. Excess (Arbona and Gómez-Cadenas, 2012).…”