Assessment of the viability of using saline reclaimed water in grapefruit in medium to long term
Cristina Romero-Trigueros | Pedro A. Nortes | Francisco Pedrero | Oussama Mounzer | Juan J. Alarcón | Jose M. Bayona | Emilio Nicolás
<p>Citrus trees are strongly affected by salinity, especially in countries where irrigation is required as a semi-arid Mediterranean agronomic region. The aims of the study were i) to identify the best reliable plant-based water status indicator for field grown grapefruit trees irrigated with saline reclaimed water during five years of cultivation by measuring seasonal changes in physiological parameters (<em>i.e</em>. gas exchange and stem water potential measurements), leaf structural traits (<em>i.e</em>. leaf chlorophyll content, area-based leaf nitrogen and area-based dry mass), phytotoxic elements and yield; ii) to estimate phytotoxicity thresholds at leaf level. Our results showed that the chlorophyll content was the parameter with the highest number of measures with significant differences (<em>p</em>≤0.05, ANOVA) between trees irrigated with reclaimed water and control trees throughout growing stages. Moreover, Chl <em>a</em> increased linearly with area-based leaf nitrogen (<em>R<sup>2</sup></em>=0.63; <em>p</em><0.001) and area-based dry mass (<em>R<sup>2</sup></em>=0.64; <em>p</em><0.001). We also determined the salt-induced phytotoxicity thresholds at which a reduction in yields occurs; these levels were Na: 0.1 g/100 g, Cl: 0.6 g/100 gand B: 100 ppm. In conclusion, we revealed the importance of leaf chlorophyll measurements as a significance diagnostic indicator of salt stress on field grown grapefruit trees. This parameter was also related to plant-based water status indicators such as stem water potential, stomatal conductance and net photosynthesis. Additionally, a salt accumulation potential at leaf level was shown, leading to possible risk in crop sustainability in the medium to long term.</p>
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