Zea mays L. amylacea from the Lluta Valley (Arica-Chile) tolerates salinity stress when high levels of boron are available

Abstract

Elevated levels of boron occurring naturally in soil or irrigation waters are detrimental to many crops grown in agricultural regions of the world. If such levels of boron are accompanied by conditions of excessive salinity, as occurs in the Lluta valley in Northern Chile, the consequences can be drastic for crops. A variety of sweet corn from this valley (Zea mays L. amylacea) has arisen as a consequence of practiced seed selection, suggesting that it is extremely tolerant to high salt and boron levels. In the present study, seeds of Zea mays L. amylacea were collected in order to study their physiological mechanisms of tolerance to high levels of NaCl and boron. Concentrations of 100 and 430 mM NaCl and 20 and 40 mg kg −1 boron were imposed as treatments. The plants did not exhibit symptoms of toxicity to either NaCl and boron during the 20 days of treatment. Na + accumulation was substantial in roots, while boron was translocated to leaves. Boron alleviated the negative effect of salinity on tissue K + and maintained membrane integrity. The higher values of water potential seem to be related to the capacity of this ecotype to maintain a better relative water content in leaves. Despite the fact that boron enhanced slightly the effect of salinity on CO 2 assimilation, no effect on photochemical parameters was observed in this ecotype. Osmotic adjustment allows this ecotype to survive in high saline soils; however the presence of boron makes this strategy unnecessary since boron contributed to the maintenance of cell wall elasticity.Abbreviations: A -net CO 2 assimilation rate; Ci -intercellular CO 2 concentration; EC (%) -percentage of electrolyte leakage; ε -modulus of elasticity at full hydration; F v /F m -maximum quantum yield of PSII; pturgor potential; s -osmotic potential; 100 s -osmotic potential at full turgor; 100 s − 100c s -degree of osmotic adjustment; w -leaf water potential; g s -stomatal conductance; qP, qN -coefficients of photochemical and non-photochemical quenching, respectively; PSII -quantum fluorescence yield; RWC -relative water content.

NaCl salinity-induced changes in water status, ion contents and photosynthetic properties of Shepherdia argentea (Pursh) Nutt. seedlings

“…The close relationship between P N and Na + concentration in leaf tissue was reported by Iqbal and Ashraf (2005), indicating that P N was affected by Na + in the leaf mesophyll. Salinity-induced excessive accumulation of Na + in the leaves of plants which was also obtained in the present study ( Figure 2); it is in agreement with the opinion that high accumulation of Na + in the cytoplasmor chloroplast can affect the integrity and function of photosynthetic membranes, when the vacuole can no longer sequester toxic ions (Bastías et al 2004). Moreover, the reduced photosynthesis at high salinity could be also attributed, in part, to the reduced content of K + (Figure 2) which is indispensable in maintaining the steady-state photosynthetic rate and contributes to better regulation of stomata opening (Stępień and Kłbus 2006).…”

“…Significant reduction of RWC in leaves of plants treated with 400 and 600 mmol/l (Figure 1) indicated that salinity also resulted in dehydration at cellular level and dehydration symptoms were greater in higher NaCl concentration treatment because of the increasing cellular water loss. Ion uptake is the cheapest form of osmotic adjustment under soil saline conditions, but it could also lead to problems of decline in leaf function and ionic imbalance and toxicity (Bastías et al 2004, Yildirim et al 2009). In particular, salinity alters uptake and absorption rates of all mineral nutrients resulting in deficiency symptoms.…”

“…The contents of Na + and K + in leaves were determined from dry matter and were quantified by an inductively coupled plasma optical emission spectrometry (ICP-OES, Leeman Labs Inc., NH, USA) after nitric-perchloric acid (1%) digestion (Bastías et al 2004).…”

“…The main negative effects of high salinity that influence plant growth and development are photosynthesis inhibition (Sharma et al 2005), water deficit (Suárez and Medina 2008), ion toxicity associated with excessive Cl -and Na + (Afzal et al 2008, Patel andPandey 2008), interference with nutrition leading to nutrient imbalance (Misra et al 1997). Bastías et al (2004) have reported that high concentrations of salt disrupt homeostasis in water relations and change the ion distribution at both cellular and whole plant levels. Later, altered water homeostasis leads to molecular damage, growth arrest and even death.…”

Cultivo De Tomate (Lycopersicon Esculentum Mill.) Hidropónico Con Agua Desalinizada Y Desborificada en El Valle De Lluta

“…Similares resultados fueron reportados por Edelstein et al (2005) trabajando con plantas de melón y CE de 1,8 y 4,6 dS m -1 y concentraciones crecientes de boro hasta 10 mg L -1 . Bastías et al (2004) e Ismail (2003 obtuvieron resultados similares trabajando con plantas de maíz y concentraciones de boro de hasta 40 mg kg -1 en el suelo, viéndose disminuido el efecto tóxico del boro con concentraciones de NaCl superiores a 100 mM. Los resultados obtenidos con este ensayo sólo muestran un efecto tampón de la salinidad sobre el exceso de boro en la concentración de sólidos solubles de los frutos, mientras que en el resto de los parámetros medidos la combinación de salinidad con boro resulta en un aumento no significativo de los valores por sobre los valores del tratamiento T2 (exceso de boro).…”