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Scanning ion‐selective electrode technique and X‐ray microanalysis provide direct evidence of contrasting Na + transport ability from root to shoot in salt‐sensitive cucumber and salt‐tolerant pumpkin under NaCl stress
Author(s) -
Lei Bo,
Huang Yuan,
Sun Jingyu,
Xie Junjun,
Niu Mengliang,
Liu Zhixiong,
Fan Molin,
Bie Zhilong
Publication year - 2014
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/ppl.12223
Subject(s) - antiporter , stele , shoot , chemistry , vanadate , rootstock , cucurbita moschata , xylem , sodium , salt (chemistry) , cucumis , horticulture , botany , nuclear chemistry , biology , biochemistry , medicine , alternative medicine , organic chemistry , pathology
Grafting onto salt‐tolerant pumpkin rootstock can increase cucumber salt tolerance. Previous studies have suggested that this can be attributed to pumpkin roots with higher capacity to limit the transport of Na + to the shoot than cucumber roots. However, the mechanism remains unclear. This study investigated the transport of Na + in salt‐tolerant pumpkin and salt‐sensitive cucumber plants under high (200 m M ) or moderate (90 m M ) NaCl stress. Scanning ion‐selective electrode technique showed that pumpkin roots exhibited a higher capacity to extrude Na + , and a correspondingly increased H + influx under 200 or 90 m M NaCl stress. The 200 m M NaCl induced Na + /H + exchange in the root was inhibited by amiloride (a Na + /H + antiporter inhibitor) or vanadate [a plasma membrane (PM) H + ‐ ATPase inhibitor], indicating that Na + exclusion in salt stressed pumpkin and cucumber roots was the result of an active Na + /H + antiporter across the PM, and the Na + /H + antiporter system in salt stressed pumpkin roots was sufficient to exclude Na + . X‐ray microanalysis showed higher Na + in the cortex, but lower Na + in the stele of pumpkin roots than that in cucumber roots under 90 m M NaCl stress, suggesting that the highly vacuolated root cortical cells of pumpkin roots could sequester more Na + , limit the radial transport of Na + to the stele and thus restrict the transport of Na + to the shoot. These results provide direct evidence for pumpkin roots with higher capacity to limit the transport of Na + to the shoot than cucumber roots.