The Effects of Pine (Pinus sylvestris L.) Needle Surface Wax Layer Structure on Water Loss and Uptake of ¹⁴CO₂ and ³⁵SO₂

Abstract

The surfaces of current and one-year-old pine (Pinus sylvestris L.) needles from areas of different air pollution levels were examined using SEM + ED AX. It was found that abrasion of needle surfaces (using a fine hairbrush), thus destroying the wax layer structure, led to an increase in water loss and a decrease in the uptake rate of 14CC₂. This phenomenon was restricted to current-year needles.

Labelling needles with ³⁵SO₂ to obtain information on distribution of sulphur taken up between particular needle compartments revealed that particulate matter accumulated on the needle surface contributing from 6 to 15% and from 13 to 24% to the total uptake of ³⁵S0₂ by needles of shoots taken from control and polluted areas, respectively. Dust contributed from 10 to 30% of ³⁵S0₂ deposits on needle surfaces. Sulphur compounds were neither soluble nor removable with water. Generally, a significantly higher amount of sulphur was bound to waxes and particulate matter than to needle tissue. There was no evidence of sulphur leaching following needle washin with water.

X-ray fluorescence analysis of pine needle surfaces under SEM has shown some differences between both the area of the needle (stomata region and next to it) and the sampling sites. On the basis of the parameters tested, the protective role of the wax layer with regard to dust accumulation is discussed.