Abstract
Vigorous interspecific rootstocks increase nitrogen (N) uptake in tomato plants but limited information is available on xylem transport rate. Non-grafted and self-grafted tomato plants cv. Attiya and plants grafted onto an interspecific hybrid, Kaiser, were grown under growth chamber conditions and subjected to two light levels, 400 or 800 µmol PAR m−2 s−1. Plant water uptake, xylem sap NO3− content, and stem hydraulic conductance (ks) were measured after two weeks of growth. Xylem vessel number and diameter were evaluated in cross-sectional stem cuts and the theoretical xylem hydraulic conductance (kh) was calculated. Only the light level modified the xylem NO3− content. Grafting reduced ks by 84% in comparison to non-grafted plants. The water uptake rate and xylem sap NO3− content were 4.02 ± 0.66 g H2O kg−1 DW h−1 and 12.78 ± 1.16 mM, respectively, across all grafting treatments. The rootstock has a higher kh because the vessel diameter is 79.3 ± 14.4 µm while in non-grafted plants it is 62.0 ± 10.1 µm. Nitrate concentration and transport rate changes accordingly to the plant’s growth rate. The vigorous rootstock relies on larger vessels to supply the required amounts of N.
Highlights
Introduction1920s starting in Asia [1]. The main advantage of joining two genotypes (sometimes two different species) is the tolerance to abiotic and/or biotic stresses of the genotype in the bottom (the rootstock) while preserving the characteristics of the genotype on top (the scion)
The practice of grafting plants for horticultural purposes has been commercially in use since the1920s starting in Asia [1]
The analysis was based on the concentration of NO3 − in the xylem sap, the actual xylem hydraulic conductance, and the anatomical characteristics in plants grafted onto a vigorous rootstock in comparison to non-grafted and self-grafted plants
Summary
1920s starting in Asia [1]. The main advantage of joining two genotypes (sometimes two different species) is the tolerance to abiotic and/or biotic stresses of the genotype in the bottom (the rootstock) while preserving the characteristics of the genotype on top (the scion). Rootstock vessel diameter has been positively correlated to growth vigor in peach trees [21] Another piece of evidence of the importance of xylem vessel size in the capacity for xylem transport was provided in a study of the susceptibility of tomato genotypes to blossom-end rot which corresponds to a calcium deficiency explained by a limited water supply to the fruit. This implies that differences exist among varieties to supply water (and nutrients) depending on the plant’s growth rate Based on this information, the present study aimed to assess xylem nitrate transport capacity in tomato plants grafted onto a vigorous rootstock. The analysis was based on the concentration of NO3 − in the xylem sap, the actual xylem hydraulic conductance, and the anatomical characteristics (i.e., vessel number and diameter) in plants grafted onto a vigorous rootstock in comparison to non-grafted and self-grafted plants
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