Forest Decline and Air Pollution

Linking stress with macroscopic and microscopic leaf response in trees: new diagnostic perspectives.

Dry deposition and foliar leaching of mercury and selected trace elements in deciduous forest throughfall

Strategies for avoiding ion accumulation in leaves of plants grown at high concentration of NaCl (100 mol m(-3)) in the rooting media, i.e. retranslocation via the phloem and leaching from the leaf surface, were quantified for fully developed leaves of maize plants cultivated hydroponically with or without salt, and with or without sprinkling (to induce leaching). Phloem sap, apoplastic fluid, xylem sap, solutes from leaf and root tissues, and the leachate were analysed for carbohydrates, amino acids, malate, and inorganic ions. In spite of a reduced growth rate Na(+) and Cl(-) concentrations in the leaf apoplast remained relatively low (about 4-5 mol m(-3)) under salt treatment. Concentrations of Na(+) and Cl(-) in the phloem sap of salt-treated maize did not exceed 12 and 32 mol m(-3), respectively, and thus remained lower than described for other species. However, phloem transport rates of these ions were higher than reported for other species. The relatively high translocation rate of ions found in maize may be due to the higher carbon translocation rate observed for C(4) plants as opposed to C(3) plants. Approximately 13-36% of the Na(+) and Cl(-) imported into the leaves through the xylem were exported by the phloem. It is concluded that phloem transport plays an important role in controlling the NaCl content of the leaf in maize. Surprisingly, leaching by artificial rain did not affect plant growth. Ion concentrations in the leachate were lower than reported for other plants but increased with NaCl treatment.

Solute balance of a maize (Zea mays L.) source leaf as affected by salt treatment with special emphasis on phloem retranslocation and ion leaching

Effect of simulated sulfuric acid rain on yield, growth and foliar injury of several crops

Experiments were performed to show the responses of foliage of several clones of Tradescantia sp., Pteridium aquilinum, Quercus palustris, and Glycine max to simulated acid rain. These experiments were performed to (a) predict the relative sensitivities of foliage of these plants to acid rain, and (b) identify leaf surface and anatomical alterations to simulated acid rain that may be used to diagnose acid rain injury. Plants were exposed to simulated rain at pH levels of 5.7, 3.4, 3.1, 2.9, 2.7, 2.5, and 2.3.

Differential responses of plant foliage to simulated acid rain

SUMMARY
Relative rates of nutrient penetration, nutrient leaching, and cell permeability of first trifoliate leaves of Phaseolus vulgaris L. cv. Univ. of Idaho 111 were examined after exposure to simulated acidic rain. In buffer solutions 35SO42- penetrated leaves faster at pH 2·7 than at 5·7. In contrast, 86Rb+ pervaded fastest at pH 5·7, and 3H2O entered foliage at similar rates at all pH levels tested. When plants were exposed to simulated rains of various pH levels, calcium, nitrate and sulphate were preferentially leached from whole leaves by rainfalls of low pH, whereas potassium and chloride leached more at pH 5·7 and 3·4 compared with 2·7 and 2·9. Isotope tests indicated that cells within leaves were more permeable to 35SO42- and 3H2O and less permeable to 86Rb+ at pH 2·7 than at higher pH levels. These results suggest a wide diversity of leaf and cell permeability responses to various ions after exposure to acidic rain. In general, an increased rate of nutrient leaching at more acidic levels was correlated with a lower adaxial leaf resistance during leaf development.

Responses of leaves of phaseolus vulgaris l. to simulated acidic rain

Relative rates of nutrient penetration, nutrient leaching, and cell permeability of first trifoliate leaves of Phaseolus vulgaris L. cv. Univ. of Idaho 111 were examined after exposure to simulated acidic rain. In buffer solutions 35SO42- penetrated leaves faster at pH 2-7 than at 5-7. In contrast, 86Rb+ pervaded fastest at pH 5 7, and 3H20 entered foliage at similar rates at all pH levels tested. When plants were exposed to simulated rains of various pH levels, calcium, nitrate and sulphate were preferentially leached from whole leaves by rainfalls of low pH, whereas potassium and chloride leached more at pH 5 7 and 3-4 compared with 2 7 and 2 9. Isotope tests indicated that cells within leaves were more permeable to 35S042- and 3H20 and less permeable to 86Rb+ at pH 2 7 than at higher pH levels. These results suggest a wide diversity of leaf and cell permeability responses to various ions after exposure to acidic rain. In general, an increased rate of nutrient leaching at more acidic levels was correlated with a lower adaxial leaf resistance during leaf development.

Thérèse M. Curry

Papers

Differential responses of plant foliage to simulated acid rain

Responses of leaves of phaseolus vulgaris l. to simulated acidic rain

Vulgaris l. to simulated acidic rain