Effect of simulated acid rain on the epicuticular wax of Scots pine needles under northerly conditions

The long-term effects of simulated acid rain treatment (pH 4 and pH 3) on the physicochemical characteristics of the needle surfaces in a natural stand of Scots pine was investigated in the extreme north of Finland during the period 1985–1988. By the end of this period, the pH 3 treated pines had received a sulphur load of 7.48 g m−2 and a nitrogen load of 2.62 g m−2, and the pH 4 treated pines a sulphur load of 1.23 g m−2 and a nitrogen load of 0.43 g m−2 in addition to ambient deposition. No visible symptoms of acid rain injury were observed in the needles, but their growth was significantly reduced. Delayed development of the epistomatal waxes and four types of deformed stomatal complex, namely narrow, half-formed, occluded, and double-sized, were found by scanning electron microscopy. The total number of deformed stomatal complexes in the pH 4 treated pine needles was over 50% greater than in dry control specimens and over 70% greater than in water controls. The rapid erosion of young, undeveloped waxes increased needle wettability (11%) significantly, but the quantity of chloroform-soluble waxes had decreased only slightly. The effects of acid rain on the epicuticular waxes were accentuated during unfavourable growing seasons with reduced effective temperature sums. Key words: acid rain, Scots pine, epicuticular wax, wettability.

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Effects of potassium deficiency and simulated acid rain, alone and in combination, on the ultrastructure of Scots pine needles

Canadian Journal of Forest Research ◽

10.1139/x89-215 ◽

1989 ◽

Vol 19 (11) ◽

pp. 1402-1411 ◽

Cited By ~ 23

Author(s):

Toini Holopainen ◽

Pekka Nygren

Keyword(s):

Acid Rain ◽

Scots Pine ◽

Potassium Deficiency ◽

Simulated Acid Rain ◽

Sand Culture ◽

Short Term ◽

Transmission Electron ◽

Resting Period ◽

Lipid Structures ◽

Parenchyma Tissue

The effects of potassium deficiency and artificial acid precipitation, alone and in combination, on Scots pine (Pinussilvestris L.) needles were studied using transmission electron microscopy. The seedling material was grown in quartz sand culture and watered with nutrient solution containing 45, 20, 10, or 5 mg of potassium/L; the concentration of other nutrients was constant and equally available for all seedlings. A portion of the seedlings from each group received consecutive acidified water spraying of pH 4.5, 4.0, 3.5, and 3.0, each for 4 days with a 3-day resting period between applications. The potassium deficiency caused an increase in the proportional vacuolar space and severe vesiculation of the tonoplast. Irregularly shaped lipid structures increased in number in the cytoplasm, and lipid bodies also appeared in the vacuoles and occasionally in the chloroplasts. The symptoms related to potassium deficiency were more severe in the transfusion parenchyma cells than in the mesophyll. The lowest level of potassium produced almost complete disorganization of the cellular structures in the transfusion parenchyma tissue, but severe changes were also seen in the mesophyll. The simulated acid rain treatment caused the formation of protrusions in the chloroplasts and an increase in irregularly shaped lipid structures in the cytoplasm throughout the mesophyll tissue, but no clear symptoms were observed inside the bundle sheath. In general, the changes caused by acid rain in the chloroplasts were slight and did not cause serious disorganization of these organelles. When the seedlings were exposed to combination treatment, the typical symptoms of both exposures were observable. The results suggest that the stresses caused by potassium deficiency and short-term foliar acid rain treatment can be distinguished in the needle ultrastructure.

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