Abstract
Boron (B) excess frequently impair plant performances and their productivity; in particular in arid and semi-arid environments. In the present experiment; hydroponically-grown ‘Granny Smith’ apple plants grafted on M9 rootstock were treated with optimal (25 μΜ) or excess (400 μΜ) B for 116 days to evaluate allometric responses of plants to B toxicity and to highlight physiological (photosynthesis and chlorophyll fluorescence) and biochemical (pigment content and sugar metabolism) responses of apple plants to B excess. Boron accumulated principally in top > middle > basal stems and leaves of high-B-stressed plants. Notably, the stem dramatically accumulated a higher level of B, as an attempt to preserve leaves, especially the youngest from further B accumulation. B accumulation seriously affected photosynthesis of younger leaves and caused both stomata (reduced stomatal conductance) and biochemical (reduction of apparent CO2 use efficiency and pigment content) limitations and altered the photochemistry and energy partitioning in photosystem II. Boron excess altered leaf sugar proportion; increasing the accumulation of non-translocating sugars such as glucose and fructose. Our dataset adds knowledge on the effect of B excess in apple tree and poses serious concerns about the possible effect of B in altering sugar metabolism; which, in turn, can strongly affect fruit production of this worldwide-cropped species.
Highlights
The critical role of boron (B) for optimal plant growth has been established since the 1920s [1]
High concentration of B in the nutrient solution (400 μM) caused a significant reduction in root biomass in terms of Dry weight (DW) compared to 25 μM B-control treatment
Measurements of aboveground plant parts, such as leaves, scion’s stems and rootstock’s stem, did not show any biomass changes between the two B treatments, but the ratio between aboveground/underground plant biomass was significantly increased in B-excess treated plants with respect to controls (Table 1)
Summary
The critical role of boron (B) for optimal plant growth has been established since the 1920s [1]. The main sources of B enrichment in the environment are the weathering of B-containing minerals and the geothermal steams, which enrich B soil and water [4,5]. The most impactful source of high-concentrated B (on average 4.6 mg L−1 B) is the seawater. From other nutrient elements, environmental B excess in the soil, is slightly affected by human activities when correlated with the extend of environmental B enrichment derived from natural sources [2,8]. Plant species show extremely high variability in responses to B in the soil. Adequate tissue B concentrations for the optimal plant growth of monocots can range from 1 to 6 mg kg−1 , whereas, dicots can range from 20 to 70 mg kg−1 , demonstrating the broad extent of B concentration that can lead to toxicity effects [6]. Considerable tolerance to B excess has been observed among species [9] and genotypes [10,11,12,13,14,15,16,17]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
