Effects of serpentine soil factors on Virginia pine (Pinus virginiana) seedlings

Our plain-English summary of Effects of serpentine soil factors on Virginia pine (Pinus virginiana) seedlings, by S.P. Miller, J.R. Cumming (Tree Physiology, 2000).

The study

• Authors: S.P. Miller, J.R. Cumming
• Journal: Tree Physiology
• Published: 2000;20(16):1129-35
• Cited by: 10 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Effects of simulated serpentine soil conditions (elevated Mg:Ca ratio and Ni concentration) on seedlings from populations of Virginia pine (Pinus virginiana Mill.) from serpentine and non-serpentine sites were evaluated in sand culture. We determined (1) how seedlings are affected by elevated Mg:Ca ratio and Ni concentrations, (2) if there are interactive effects between Mg:Ca ratio and Ni concentrations on seedling growth, needle pigment concentrations, and nutrition, and (3) if Virginia pine populations from serpentine areas are edaphic ecotypes. A Mg:Ca ratio of 5 and 50 microM Ni both reduced seedling growth compared with control seedlings grown in the presence of the standard Mg:Ca ratio of 0.5 and no Ni. Interactive effects between Mg:Ca ratio and Ni concentrations were highly significant for growth, foliar pigments, and needle and root elemental concentrations. Nickel-mediated reductions in growth and foliar pigment concentrations were less at the serpentine Mg:Ca ratio of 5 than at the standard (non-serpentine) Mg:Ca ratio of 0.5. Foliar N was reduced by Ni concentrations as low as 10 microM, and foliar and root K, Ca and P concentrations were significantly reduced by Ni concentrations above 25 microM, with greater reductions at a Mg:Ca ratio of 0.5 than at a Mg:Ca ratio of 5. There were no population x serpentine soil factor interactions for seedling growth, foliar pigment concentrations, or nutrition, suggesting that seedlings from trees growing on serpentine soils are not edaphic ecotypes. We conclude that serpentine conditions present at the site of seed collection have not resulted in the selection of edaphic ecotypes of Virginia pine with respect to Mg:Ca ratio and Ni concentration.

In plain English

This greenhouse experiment tested how two serpentine-soil features, a high magnesium-to-calcium (Mg:Ca) ratio and elevated nickel, affected Virginia pine seedlings. The article does not discuss asbestos. Seed came from trees on Pennsylvania's Conowingo serpentine barrens and from a non-serpentine seed orchard. For 9 weeks, sand-grown seedlings got a standard Mg:Ca ratio of 0.5 with 0 or 50 µM nickel, or a serpentine ratio of 5.0 with 0, 10, 25 or 50 µM. Without nickel, shoot and root biomass were about 20% lower at the serpentine ratio. Versus no nickel at the same ratio, 50 µM nickel cut shoot and root biomass by 70% and 89% at the standard ratio and by 22% and 40% at the serpentine ratio. At the serpentine ratio, 10 µM nickel cut needle nitrogen by 30% versus no nickel. No statistically significant differences were detected between the seed sources' responses. The authors concluded that serpentine conditions at the seed-collection site had not selected for Virginia pines adapted to its Mg:Ca ratio and nickel (edaphic ecotypes). They noted that root nutrient results in the harshest treatment were hard to interpret.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: greenhouse experiment on tree seedlings grown in sand culture with controlled nutrient solutions (plant physiology study)
• Who was studied: Virginia pine (Pinus virginiana) seedlings from two seed sources. The serpentine source was trees on the Conowingo pine barrens, Lancaster County, PA, with seed collected in fall 1996. The general (non-serpentine) source was a seed orchard at Penn Nursery, Spring Mills, PA. There were 9 seedlings of the general population and 8 of the serpentine population. Seedlings were grown in a greenhouse in Morgantown, WV, in 1998, and the experiment lasted 9 weeks.
• Exposure: Simulated serpentine soil chemistry, not asbestos fibers. Seedlings at the serpentine Mg:Ca ratio of 5.0 received nickel at 0, 10, 25 or 50 µM. Seedlings at the standard Mg:Ca ratio of 0.5 received only 0 or 50 µM nickel.
• Main results:
  • In seedlings given no nickel, shoot and root biomass were about 20% lower at the serpentine Mg:Ca ratio of 5 than at the standard ratio of 0.5.
  • Each of these reductions is relative to seedlings given 0 µM nickel at the same Mg:Ca ratio. At the standard Mg:Ca ratio, 50 µM nickel reduced shoot biomass by 70% and root biomass by 89%. At the serpentine Mg:Ca ratio, it reduced shoot biomass by 22% and root biomass by 40%.
  • Seedlings given 50 µM nickel showed chlorosis (yellowing), with significantly lower needle chlorophyll a and b.
  • The most sensitive measure was needle nitrogen. In seedlings at the serpentine Mg:Ca ratio given 10 µM nickel, it was reduced by 30%. The comparison is with seedlings given no nickel at that ratio, as shown by the article's Table 3 values of 34.3 mg per g at 0 µM and 24.0 mg per g at 10 µM.
  • At the standard Mg:Ca ratio, 50 µM nickel reduced needle phosphorus by 54% and root phosphorus by 75%.
  • At the serpentine Mg:Ca ratio, 50 µM nickel reduced needle phosphorus by 36% and root phosphorus by 20%.
  • No statistically significant population-by-treatment interactions were detected between the serpentine and non-serpentine seed sources (P values 0.269 to 0.998). The authors said this does not support the hypothesis that edaphic ecotypes are present.
  • The authors found that the elevated (serpentine) Mg:Ca ratio slightly harmed seedling growth but reduced nickel toxicity.
• The authors' conclusion: The authors concluded that serpentine conditions at the seed-collection site had not resulted in the selection of edaphic ecotypes of Virginia pine with respect to Mg:Ca ratio and nickel concentration. Edaphic ecotypes are populations adapted to particular soils. The authors noted that other factors, such as shallow rooting depth, might be selective forces at these sites.
• Limitations the authors state:
  • Roots in the 50 µM nickel plus standard Mg:Ca ratio treatment were small and necrotic, making root nutrient results for that treatment difficult to interpret.
  • A slight increase in root potassium at the standard ratio with 50 µM nickel may be an artifact of the small tissue sample size for that treatment.
  • Slight growth differences between the two populations may have reflected differences in initial seed mass.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile.

Medical terms in this study, explained in our Lexicon: Serpentine Group.

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