Data from: Drought stress induces salicylic acid accumulation, altering monoterpene profile and suppressing resin duct formation in Engelmann spruce
Data files
Jun 29, 2026 version files 18.44 KB
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experiment1_water_deprivation.csv
2.88 KB
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experiment2_chronic_water_stress.csv
9.42 KB
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experiment3_meja_and_resin_ducts.csv
2.83 KB
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README.md
3.30 KB
Abstract
Drought is a critical stressor on plants and is often observed preceding large-scale insect outbreaks in forest ecosystems. Whether plant physiological mechanisms underlie this pattern remains uncertain; environmental conditions affect the growth rate of insect populations but also have consequences for plant defense phenotypes. To investigate the latter, we experimentally applied water stress to test relationships between drought, salicylic acid (SA) accumulation, and tree resistance factors including secondary metabolite (monoterpene) concentrations and formation of traumatic resin ducts in Engelmann spruce (Picea engelmannii), a widespread forest tree in western North America. Three key findings emerged. First, both acute and chronic water stress reduced stem water potentials, with evidence for loss of photosynthetic function as water potentials declined below -2.0 MPa. Negative water potential was associated with an increase in the concentrations of SA in both needles and stem phloem, but this trend was stronger in needles. Second, under water stress elevated SA concentrations were associated with increased concentrations of several structurally similar monoterpenes in needles and stem phloem, including β-phellandrene, δ-3-carene, γ-terpinene, and terpinolene. These trends were stronger in stem phloem than in needles. Lastly, chronic water stress inhibited the ability of P. engelmannii to form traumatic resin ducts in response to methyl jasmonate, a ubiquitous elicitor of inducible plant defenses. Collectively, our experiments show endogenous upregulation of SA in response to water stress in Engelmann spruce, resulting in changes to composition of volatile profiles and potentially suppressing induction of defense systems. These phenotypic changes may affect the performance of phloeophagous forest insects by altering plant resistance traits associated with defensive competency in response to herbivory.
Dataset DOI: 10.5061/dryad.cnp5hqck4
Description of the data and file structure
Datasets represent a set of three greenhouse studies investigating the effects of experimental drought stress on photosynthesis, salicylic acid concentrations, monoterpene concentrations, and resin duct formation in Engelmann spruce seedlings.
Files and variables
File: experiment1_water_deprivation.csv
Description: A greenhouse test of acute water deprivation, where water was withheld from seedlings over time and water potentials, salicylic acid concentrations, and photosynthetic rates were recorded.
Variables
- date: the date on which destructive samples were collected.
- mpa: stem water potential, megapascals
- A: photosynthetic rate, mmol CO2 fixed per m2 s -1
- tissue: tissue type, where R = root, S = stem phloem, and F = foliar tissue/needles
- SAMPLE_ID: the unique sample label
- sa: salicylic acid concentration, micrograms per gram tissue
File: experiment2_chronic_water_stress.csv
Description: A greenhouse experiment analyzing variation in salicylic acid and monoterpenes in seedlings that were well-watered and those experiencing chronic drought stress.
Variables
- tissue: tissue type, where S = stem phloem and F = foliar tissue/needles
- sample_ID: the unique sample label
- a.pinene: concentration of alpha pinene, micrograms per gram
- b.pinene: concentration of beta pinene, micrograms per gram
- sabinene: concentration of sabinene, micrograms per gram
- myrcene: concentration of myrcene, micrograms per gram
- carene: concentration of delta-3-carene, micrograms per gram
- b.phell: concentration of beta phellandrene, micrograms per gram
- g.terp: concentration of gamma terpinene, micrograms per gram
- terpinolene: concentration of terpinolene, micrograms per gram
- linalool: concentration of linalool, micrograms per gram
- camphene: concentration of camphene, micrograms per gram
- sum_terps.ug.ml: concentration of all monoterpenes, summed, micrograms per gram
- water_trt: watering treatment, where low = 0.2 g H2O/g soil and high = 0.8 g H2O/g soil
- day: the day of the test on which experimental units were destructively sampled
- mpa: stem water potential, megapascals
- SA.ug.mL: salicylic acid concentration, micrograms per milliliter
File: experiment3_meja_and_resin_ducts.csv
Description: A greenhouse experiment where methyl jasmonate was applied to seedlings under chronic drought stress or those that were well-watered.
Variables
- ID Number: the unique sample label
- Watering Treatment: watering treatment, where low = 0.2 g H2O/g soil and high = 0.8 g H2O/g soil
- Resin Duct Classification (0-3): resin duct category where 0 = no traumatic resin ducts, 1 = resin ducts bisecting < 20 % of the growth increment, 2 = resin ducts bisecting between 20 and 90 % of the growth increment and 3 = resin ducts bisecting > 90 % of the growth increment.
- week: the week during which destructive samples were taken.
Code/software
MS Excel, Notepad, or any software that will open .csv files.