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Transport of zinc and manganese to developing wheat grains
Author(s) -
Pearson J. N.,
Rengel Z.,
Jenner C. F.,
Graham R. D.
Publication year - 1995
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.1399-3054.1995.tb00862.x
Subject(s) - girdling , xylem , phloem , peduncle (anatomy) , manganese , zinc , vascular bundle , chemistry , lemma (botany) , botany , glume , horticulture , poaceae , biology , organic chemistry
An understanding of the transport pathway used by Zn and Mn to enter developing grains may allow measures to increase the Zn and Mn content of wheat grain grown on Zn/Mn deficient soils. For this reason, transport of Zn and Mn into developing grains of wheat ( Triticum aestivum L. cv. Aroona) was investigated. Detached ears (18–22 days post‐anthesis) were cultured for 48 h in a solution containing 185 kBq of 65 Zn and 185 kBq of 54 Mn. Transport of 65 Zn to the grain was unaffected by removal of glumes but was slightly reduced after the lemma was removed. Heat girdling the peduncle slightly reduced the amount of 65 Zn transported to the grain, whilst heat girdling the rachilla reduced transport of 65 Zn to the grain to a greater degree, suggesting phloem transport to the rachilla. The transport inhibitor CCCP (carbonyl cyanide m ‐chlorophenyl hydrazone) blocked 65 Zn transport to grain but not to lemma and glumes. Removing glumes and lemma and heat girdling the peduncle did not affect transport of 54 Mn, but transport was slightly affected by heat girdling the rachilla, indicating xylem transport. CCCP blocked transport of 54 Mn into the grain but not to lemma and glumes. It was concluded that xylem‐to‐phloem transfer of Zn occurs in the rachis and to a lesser extent in peduncle and lemma. The results suggest that the lemma may be an important site for phloem loading when the concentration of Zn within the xylem is high. The data also suggest that Mn was predominantly translocated to the spikelets in the xylem, but that transport to the grain was dependent upon membrane transport before entering the grain. Phloem loading of Mn into the grain vascular system may have occurred at the site of xylem discontinuity in the floral axis.