Parameters Symptomatic for Boron Toxicity in Leaves of Tomato Plants

Abstract

The incidence of boron (B) toxicity has risen in areas of intensive agriculture close to the Mediterranean sea. The objective of this research was to study the how B toxicity (0.5 and 2 mM B) affects the time course of different indicators of abiotic stress in leaves of two tomato genotypes having different sensitivity to B toxicity (cv. Kosaco and cv. Josefina). Under the treatments of 0.5 and 2 mM B, the tomato plants showed a loss of biomass and foliar area. At the same time, in the leaves of both cultivars, the B concentration increased rapidly from the first day of the experiment. These results were more pronounced in the cv. Josefina, indicating greater sensitivity than in cv. Kosaco with respect to excessive B in the environment. The levels of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mtext>O</mml:mtext><mml:mn>2</mml:mn></mml:msub><mml:msup><mml:mtext> </mml:mtext><mml:mrow><mml:mo>•</mml:mo><mml:mo>−</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math> and anthocyanins presented a higher correlation coefficient (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>r</mml:mi><mml:mo>&gt;</mml:mo><mml:mn>0.9</mml:mn></mml:mrow></mml:math>) than did the levels of B in the leaf, followed by other indicators of stress, such as GPX, chlorophyll b and proline (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>r</mml:mi><mml:mo>&gt;</mml:mo><mml:mn>0.8</mml:mn></mml:mrow></mml:math>). Our results indicate that these parameters could be used to evaluate the stress level as well as to develop models that could help prevent the damage inflicted by B toxicity in tomato plants.