Keith F. Jensen

Changes in yellow poplar stomatal resistance with SO2 and O3 fumigation

Abstract The effect of O 3 and SO 2 on leaf diffusive resistance (LDR) of yellow poplar seedlings was studied at 40% and 80% humidity. LDR was measured at 0800, 0900, 1100, 1400 and 1600 h on seedlings fumigated from 0900 h until 1400 h each day for five consecutive days. Fumigation treatments were control, 0·15 μl litre −1 O 3 , 0·25 μl litre −1 SO 2 and 0·15 μl litre −1 O 3 + 0·25 μl litre −1 SO 2 . No change in daily LDR response was observed for the seedlings at 40% humidity. At 80% humidity, daily LDR response of seedlings in all four treatments changed significantly over the 5 days of the experiment. The range of the LDR values and the daily response curves both changed. The higher humidity apparently caused the stomata to open so that more pollutants could enter the leaves. The pollutants then interacted with the leaf cells and modified the stomatal response.

Growth analysis of hybrid poplar cuttings fumigated with ozone and sulphur dioxide

Abstract To measure the influence of air pollutants on the partitioning of photosynthate into leaves or stems and roots, softwood cuttings of a hybrid poplar clone ( Populus deltoides Bartr. × P. trichocarpa Torr. and Gray) were fumigated with either zero pollutants, 0·15 ppm ozone (O 3 ), 0·25 ppm sulphur dioxide (SO 2 ) or 0·15 ppm O 3 plus 0·25 ppm SO 2 for 12 h a day for 7 weeks. Cuttings were harvested at 3- or 4-day intervals and leaf area and dry weights of leaves, stems and roots were determined. Relative growth rate ( K W ), relative leaf area expansion rates ( K A ) and relative leaf weight growth rates ( K L ) were calculated. Values for K W and K L were reduced from approximately 0.04 g g −1 day −1 for the control cuttings to near zero with the O 3 plus SO 2 gas fumigation. K A was reduced from 0.04 cm 2 cm −1 day −1 for the control cuttings to zero for the O 3 plus SO 2 gas treatment. As K W ) decreased among treatments, K A and K L decreased by a proportional amount. These results indicate that even though total biomass was reduced by air pollutants, the proportion of total available photosynthate used in leaf growth remained nearly constant.

Effects of sulfur dioxide and ozone on growth of hybrid poplar leaves.

Hybrid poplar plants were exposed to 0.5 ppM SO/sub 2/, 0.25 ppM O/sub 3/ or 0.5 ppM SO/sub 2/ + 0.25 ppM O/sub 3/ 12 hr/day for 24 days to ascertain their effects on leaf growth and abscission. The data revealed that both O/sub 3/ alone and O/sub 3/ + SO/sub 2/ promoted leaf abscission, while SO/sub 2/ alone had no effect. Leaf area and dry weight were reduced while leaf abscission was stimulated by ozone fumigation. The interaction found between SO/sub 2/ and O/sub 3/, with all the parameters measured, was an antagonistic relationship in which SO/sub 2/ reduced the toxic effect of ozone. The data analyzed, in relation to leaf position, demonstrated that ozone did not affect development of the six youngest rapidly growing leaves. However, ozone significantly reduced both leaf area and leaf weight, at later stages of development. 14 references, 4 tables.

Response of eastern hardwood species to ozone, sulfur dioxide and acid precipitation

Recent reports and observations of dieback, declines, and reduced growth in forests in the Eastern States have lead to an attempt to determine if atmospheric deposition is a major causal factor in these disorders. In the red spruce and southern pine forest where these abnormalities are either visible or have been documented by research data, studies are underway to determine the mechanisms involved and the role of atmospheric deposition. In the eastern hardwood forest there are reasons to suspect similar phenomenon, but because of the more complex nature and the wider species diversity in these forests the declines are more difficult to document. Another factor that increases the difficulty in determining whether atmospheric deposition is affecting hardwood forests is that tree responses to most stress factors, including atmospheric deposition, are very similar. The objective of this study was to determine the relative sensitivity and symptom development of 10 hardwood tree species to ambient levels of common gaseous pollutants.

Responses of hybrid poplar cuttings to chronic and acute levels of ozone

Hybrid poplar cuttings were exposed to either 0·15 ppm ozone for 6 weeks or 1 ppm ozone for 2, 4, or 8 h. The chronic ozone treatment reduced growth by 50% and caused injury to 75 of the leaves. The acute ozone treatment had no effect on growth but caused injury to 70% of the leaves 48 h after fumigation.

Atmospheric Deposition Effects on Foliar Injury and Foliar Leaching in Red Spruce

The initial contact that atmospheric deposition makes with the forest occurs in the canopies of the trees. Therefore, the foliage is a primary area to look for a response to acidic deposition and ozone. Two major foliar responses are cell and tissue injury and increased leaching of foliar constituents. Pollutants initially affect physiological processes and cell ultrastructure. There are no outward signs of stress, although the tree may be weakened and growth impaired. Ultimately, if the pollutant dosage is high enough, visible symptoms appear that are characteristic of a specific pollutant or mixture of pollutants. Severely injured needles eventually may be shed. Visible foliar symptoms are probably the most widely used bioindicators of a plant’s response to air pollution stress. They appear as discolorations (e.g., chlorosis) and necroses that occur in various sizes, shapes, patterns, and locations on the leaf. Unfortunately, no one pollutant produces a unique set of foliar symptoms that are distinct from those produced by other pollutants or stresses. Foliar injury may affect processes occurring in leaves such as photosynthesis, respiration, transpiration, and foliar leaching.

Response of yellow-poplar (Liriodendron tulipifera L.) seedlings to simulated acid rain and ozone—1. Growth modifications

Abstract One-year-old yellow-poplar seedlings were exposed to 0.0, 0.05, 0.1, or 0.2 ppm ozone (O 3 ) for 8 hr on each of 3 consecutive days. On the 4th day they were treated with 1.25 cm of simulated rain at a pH of 3.0, 4.0, or 5.5. The plants were placed on a greenhouse bench for the remainder of the week. This procedure was repeated each week from late May until mid-October. Seedlings in each treatment were harvested on 15 July, 1 September, and 15 October, and leaf area, leaf weight, new-growth weight, and height were determined. Stepwise regression was used to develop a response surface for each variable at each harvest. Growth-analysis variables were calculated from the response surfaces. Both O 3 and rain acidity had an impact on growth. At the second harvest (1 September), only acidity had an impact on growth; in general, growth increased with a decrease in acidity. At the first and third harvests (15 July and 15 October), O 3 alone or in combination with rain acidity affected growth. Growth decreased with an increase in O 3 concentration or a decrease in the acidity.

Response of yellow poplar seedlings to intermittent fumigation

Abstract Yellow poplar Liriodendron tulipifera L. seedlings were treated with either clean air, 0·1 ml litre−1 O3, 0·1 ml litre−1 O3 plus 0·2 ml litre−1 SO2, or 0·1 ml litre−1 O3 plus 0·2 ml litre−1 NO2 for one or two 12-h fumigation periods per week. Ten seedlings were harvested from each treatment every 4 weeks throughout the growing season and growth curves for height, leaf area, leaf dry weight, new growth dry weight, and total dry weight were constructed. Height, leaf area, leaf dry weight, new growth dry weight, and total dry weight differed by fumigation treatments. Relative growth rate and net assimilation rate of the yellow poplar seedlings were reduced by fumigation. Seedlings moved twice a week from the glasshouse to the fumigation chambers were significantly shorter than seedlings moved only once a week.

Effects of chronic and acute exposure to sulphur dioxide on the growth of hybrid poplar cuttings

Abstract Hybrid poplar clones were fumigated in controlled-environment chambers with either 5 ppm sulphur dioxide for 1 1 2 , 3, and 6 h or with 0·25 ppm sulphur dioxide for six weeks. Multivariate analyses were made from shoot-growth data before and after treatment and on the foliar injury induced by SO 2 . Both short- and long-term fumigation produced similar plant-behaviour responses to the two SO 2 concentrations.

Effects of Fusarium canker on translocation in yellow-poplar seedlings

Abstract Yellow-poplar seedlings inoculated with Fusarium solani were exposed to 14 CO 2 , and the 14 C activity was measured 24 h later. Fusarium cankers did not cause an accumulation of photosynthate in the phloem tissue near the infection site. The inoculated seedlings contained more 14 C activity than the uninoculated seedlings, suggesting a greater photosynthetic assimilation of 14 CO 2 by the infected seedlings.