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Regulation of xylem transport of calcium from roots to shoot of maize by growth‐related demand
Author(s) -
Engels Christof
Publication year - 1999
Publication title -
journal of plant nutrition and soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 87
eISSN - 1522-2624
pISSN - 1436-8730
DOI - 10.1002/(sici)1522-2624(199906)162:3<287::aid-jpln287>3.0.co;2-n
Subject(s) - xylem , shoot , apoplast , exudate , nutrient , stele , transpiration stream , botany , meristem , transpiration , plant nutrition , chemistry , biology , horticulture , cell wall , photosynthesis , organic chemistry
The aim of the present experiments was to study the effect of growth‐related nutrient demand on Ca 2+ translocation from roots to shoot of maize ( Zea mays L.). The plants were grown under controlled environmental conditions in nutrient solution with constant Ca 2+ supply. The growth‐related demand for Ca 2+ and other nutrients was modified by growing the plants with their apical shoot meristem either at air temperature (24°C/20°C day/night) or at 14°C. Reduction of the shoot meristem temperature (SMT) to 14°C decreased shoot growth without affecting root growth in the first five days, which diminished the growth‐related demand of the shoot for nutrients per unit of roots. This decrease in shoot demand led to a reduction not only of Ca 2+ translocation rates in intact transpiring plants but also of Ca 2+ fluxes in the xylem exudate of decapitated plants. This indicates that the decrease in xylem flux of Ca 2+ at low SMT was not only the result of low transpiration‐related water flux, and thus possibly low apoplasmic bypass transport of Ca 2+ into the stele. In decapitated plants precultured at low SMT, the water flux through the roots was diminished even more than Ca 2+ flux, leading to a significant increase in the Ca 2+ concentration of the exudate, and thus presumably an increase in the Ca 2+ gradient between cytosol and apoplast of stelar parenchyma cells. When the osmotically driven water flux was reduced by addition of mannitol to the nutrient solution, Ca 2+ concentration in the exudate markedly increased, whereas Ca 2+ translocation was only slightly affected. From these results it is suggested that the decrease in Ca 2+ translocation rates at low shoot demand was not related to low water flux but to direct effects on the capacity of Ca 2+ transport mechanisms in the roots.