Compensation as a Plant Response to Ozone and Associated Stresses: An Analysis of ROPIS Experiments

Abstract

This paper examines the role that compensation plays in determining plant response to stress. In addition to exploring the compensatory responses to individual stresses, multiple stresses that induce different compensatory strategies are considered. To do this we have utilized results of many experiments conducted by the Response of Plants to Interacting Stresses (ROPIS) project. Similarities and differences in compensatory responses of plants are considered as a function of growth habits viz. herbaceous annuals, and deciduous and evergreen perennials. The predominant way that plants compensate for stress is through shifts in C allocation, with shifts toward the roots occurring in response to stresses like drought and nutrient deficiencies. Photosynthetic poisons like ozone (O3) and sulfur dioxide (SO2) will induce shifts in favor of the shoot. Plant physiological strategies for coping with stress can also lead to shifts in shoot/root ratio; these include accelerated senescence of injured leaves in favor of production of new foliage, altered leaf area and rates of photosynthesis, and N and C allocation. At the biochemical level, the mechanisms for induction of compensatory shifts are not known; however, it is likely that hormonal changes lead to altered genetic expression of protein synthesis that modify metabolism within tissues or organelles. At the whole plant level, the role of sink strength appears to be important in determining the flow of C and N in stressed plants.

Nitrogen supply as a limiting factor determining the sensitivity of Populus tremuloides Michx. to ozone stress

“…Unlike the O.,-induced loss in biomass, this shift did not correlate with growth rate, and therefore with N supply {r = 0-05). Similarly, there was no correlation between Oj-induced shift in shoot/root ratio and O.,-induced loss in biomass {r = 0-06), supporting the suggestion of Pell et al (1994) that the 03-induced shift in shoot/root ratio might be a compensatory response rather than a reflection of injury.…”

Effect of O3 on Hydraulic Architecture in Pima Cotton (Biomass Allocation and Water Transport Capacity of Roots and Shoots)

“…Numerous studies indicate that O, exposure of plants (McLaughlin and McConathy, 1983;Heggestad et al, 1988;Temple et al, 1988a;Heggestad and Lee, 1990;Kostka-Rick et al, 1993;Pell et al, 1994), specifically including upland cotton (Gossypium hirsutum L.; Oshima et al, 1979;Miller, 1988;Temple et al, 198813;Temple, 1990b), reduces plant size and commercial yield. Effects typically include reductions in leaf area, height, biomass production, and relative allocation of biomass below ground.…”

Sensitivity of seedlings of black cherry (Prunus serotina Ehrh.) to ozone in Great Smoky Mountains National Park

“…( ) individual year models, ( ) common model. (McCool & Menge, 1983;Pell et al, 1994); (2) there is an apparent lower priority by roots for photosynthate, especially under conditions of carbohydrate limitation (Laurence et al, 1994); and (3) most of the photosynthate for roots comes from leaves lower down on the stem (Dickson, 1986), which are the ones that most often show the greatest depressions in photosynthetic rates, owing to ageing and longer ozone exposure (Reich & Amundson, 1985;Pell et al, 1994). The ratio of leaf area to dry weight, or leaf area ratio (LAR), was significantly lowered by exposure to ozone in 1989, but not in 1992 (Table 3).…”