TY - JOUR
T1 - Salt stress aggravates boron toxicity symptoms in banana leaves by impairing guttation
AU - Shapira, Or
AU - Israeli, Yair
AU - Shani, Uri
AU - Schwartz, Amnon
PY - 2013/2
Y1 - 2013/2
N2 - Boron (B) is known to accumulate in the leaf margins of different plant species, arguably a passive consequence of enhanced transpiration at the ends of the vascular system. However, transpiration rate is not the only factor affecting ion distribution. We examine an alternative hypothesis, suggesting the participation of the leaf bundle sheath in controlling radial water and solute transport from the xylem to the mesophyll in analogy to the root endodermis. In banana, excess B that remains confined to the vascular system is effectively disposed of via dissolution in the guttation fluid; therefore, impairing guttation should aggravate B damage to the leaf margins. Banana plants were subjected to increasing B concentrations. Guttation rates were manipulated by imposing a moderate osmotic stress. Guttation fluid was collected and analysed continuously. The distribution of ions across the lamina was determined. Impairing guttation indeed led to increased B damage to the leaf margins. The kinetics of ion concentration in guttation samples revealed major differences between ion species, corresponding to their distribution in the lamina dry matter. We provide evidence that the distribution pattern of B and other ions across banana leaves depends on active filtration of the transpiration stream and on guttation.
AB - Boron (B) is known to accumulate in the leaf margins of different plant species, arguably a passive consequence of enhanced transpiration at the ends of the vascular system. However, transpiration rate is not the only factor affecting ion distribution. We examine an alternative hypothesis, suggesting the participation of the leaf bundle sheath in controlling radial water and solute transport from the xylem to the mesophyll in analogy to the root endodermis. In banana, excess B that remains confined to the vascular system is effectively disposed of via dissolution in the guttation fluid; therefore, impairing guttation should aggravate B damage to the leaf margins. Banana plants were subjected to increasing B concentrations. Guttation rates were manipulated by imposing a moderate osmotic stress. Guttation fluid was collected and analysed continuously. The distribution of ions across the lamina was determined. Impairing guttation indeed led to increased B damage to the leaf margins. The kinetics of ion concentration in guttation samples revealed major differences between ion species, corresponding to their distribution in the lamina dry matter. We provide evidence that the distribution pattern of B and other ions across banana leaves depends on active filtration of the transpiration stream and on guttation.
KW - Apoplast
KW - Bundle sheath
KW - Hydathodes
KW - Lamina marginal vein
KW - Symplast
KW - Xylem
UR - http://www.scopus.com/inward/record.url?scp=84871928178&partnerID=8YFLogxK
U2 - 10.1111/j.1365-3040.2012.02572.x
DO - 10.1111/j.1365-3040.2012.02572.x
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C2 - 22765264
AN - SCOPUS:84871928178
SN - 0140-7791
VL - 36
SP - 275
EP - 287
JO - Plant, Cell and Environment
JF - Plant, Cell and Environment
IS - 2
ER -