title: Salt stress aggravates boron toxicity symptoms in banana leaves by impairing guttation.
abstract: 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.
authors: The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Hebrew University of Jerusalem, Rehovot 76100, Israel.
authors: O R
authors: OR
authors: Shapira
authors: Yair
authors: Y
authors: Israeli
authors: Uri
authors: U
authors: Shani
authors: Amnon
authors: A
authors: Schwartz
mesh_terms: D001895:Boron / Q000633:toxicity*; D007700:Kinetics; D058503:Mesophyll Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D008903:Minerals / Q000378:metabolism; D028521:Musa / Q000033:anatomy & histology / Q000187:drug effects / Q000502:physiology*; D053147:Plant Exudates / Q000378:metabolism*; D018515:Plant Leaves / Q000033:anatomy & histology / Q000187:drug effects / Q000502:physiology*; D011189:Potassium Chloride / Q000494:pharmacology; D012965:Sodium Chloride / Q000494:pharmacology*; D012996:Solutions; D013312:Stress, Physiological / Q000187:drug effects*; D013997:Time Factors
chemical_list: D008903:Minerals; D053147:Plant Exudates; D012996:Solutions; D012965:Sodium Chloride; D011189:Potassium Chloride; D001895:Boron