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Investigating the in vivo calcium transport path to developing potato tuber using 45 Ca: a new concept in potato tuber calcium nutrition
Author(s) -
Busse James S.,
Palta Jiwan P.
Publication year - 2006
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.2006.00741.x
Subject(s) - stolon , solanum tuberosum , xylem , transpiration stream , calcium , phloem , shoot , botany , solanaceae , horticulture , tubercle , solanum , biology , chemistry , transpiration , biochemistry , photosynthesis , genetics , organic chemistry , gene , bacteria , bacilli
Calcium is believed to be transported with water in the xylem. Consistent with this proposal, low‐transpiring organs such as potato Solanum tuberosum tubers are known to suffer from calcium deficiency. Although roots on tubers and stolons have been shown to supply water to tubers, there is no direct evidence for the calcium transport pathway to tubers. Both a xylem and a phloem transport pathway have been suggested. We investigated in vivo calcium transport to developing potato, cv. Dark Red Norland and cv. Russet Burbank, tubers using 45 Ca in a controlled environment facility. Whole plant split pot experiments allowed the placement of 45 Ca either in the main (basal) root or the tuber and stolon areas of the pot. The results showed that 45 Ca was transported to the shoot with the transpiration stream from both areas but was not re‐translocated to tubers or the main (basal) root system even 57 days after 45 Ca application. Radioactivity could only be detected in the tuber when 45 Ca was fed to the stolon and tuber area. When 45 Ca was fed to specific tubers, radioactivity was detected in the aerial shoot; however, no activity was detected in other tubers or the main (basal) roots. In another set of experiments, roots on a stolon near a tuber were precisely fed 45 Ca and Safranin O. The radioactive signal exactly overlapped the water transport pathway in the tuber marked with Safranin O dye, suggesting that water and calcium can be simultaneously transported from stolon roots to the tuber. No transport of 45 Ca across the tuber periderm was detected 8 days after 45 Ca was applied to the tuber periderm. This indicated that no significant transport of calcium occurs from the soil across the periderm. Our results provide evidence that: (1) calcium is not re‐translocated via the phloem from the aerial shoot tubers and main (basal) roots; (2) the main root system does not supply calcium to the tuber; (3) calcium is not transported across the periderm to the interior tuber tissue; (4) calcium is transported to the tuber via the xylem along with water, and the roots on the stolon associated with the tuber supply water and calcium to the developing tuber; and (5) transpirational demand is a significant determinant of calcium distribution within the plant.