Photosynthesis and rhizome carbohydrate concentrations of switchgrass grown from reserve-depleted rhizomes
Data files
Sep 07, 2023 version files 97.57 KB
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README.md
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SSIII_dryad.csv
Abstract
A long-standing question in perennial grass breeding and physiology is whether yield improvement strategies could compromise winter survival. Perennial grasses rely on the pool of carbohydrates accumulated in storage organs from the previous growing season for winter maintenance and spring regrowth. Yield improvement strategies could reduce winter survival if they increase biomass and grain yields at the expense of carbon allocation to storage. Therefore, it is crucial to better understand the dependence of regrowth on storage reserves. We experimentally depleted switchgrass (Panicum virgatum L.) rhizome reserves by storing rhizomes for two weeks at 5 °C (control treatment) and 25 °C (reserve-depleted treatment). During the storage period rhizome respiration was 5.3x higher at 25 °C (0.010 μmol CO2 g-1 min-1 at 5 °C vs. 0.054 μmolCO2 g-1 min-1 at 25 °C; P < 0.0001) and the starch content was depleted by 30% by the end of storage. Surprisingly, reserve-depleted switchgrass had 60 % larger leaf area, and produced ~40% more aboveground biomass than control plants. In addition, it restored its rhizome starch reserves to pre-storage levels. Switchgrass showed a large plasticity amongst its source-sink components to buffer the imposed reserve depletion. It increased plant photosynthesis by increasing the photosynthetic leaf area while keeping photosynthesis constant on a leaf area basis and readjusted the timing and activity of sink organs to maintain a constant allocation of carbon to storage that was greater than the control treatment. These results suggest that switchgrass, and potentially other perennial grasses, largely over-invest in storage reserves, therefore, current breeding strategies in perennial grasses aimed to extend the growing season should not compromise crop persistence. Our study also has implications on long-term yield dynamics as it highlights sink-limitations as potential driver of the yield decline commonly observed in perennial grasses 5+ years after cultivation.
README
A 30% reduction in switchgrass rhizome reserves did not decrease biomass yield.
Dataset compiles switchgrass (Panicum virgatum) carbohydrate (Glucose, sucrose and starch content in leaves and rhizome), development (tillering, leaf development flowering, and senescence), photosynthesis (net CO2 assimilation, stomatal conductance to water, and Photosystem II efficiency) and biomass data (Aboveground, root, rhizome biomass, leaf area) measured repeatedly over switchgrass growth cycle. Plants were grown from reserve-depleted and control rhizomes. Control and reserve-depleted rhizomes were stored at 5 C and 25 C, respectively, for 14 days. The aim of the study was to study the effects of switchgrass rhizome reserves on physiology and development.
Description of the data and file structure
Data are presented in a long format. Each row corresponds to an observation of an individual plant (RhiID).
Repeated measurements were taken for development and photosynthesis, biomass data collection was destructive.Columns represent:
FieldRhiHarvest: Date when rhizomes were harvested from the field (m/d/YYYY)
ExperimentStart: Date when rhizomes were stored at the different temperatures (m/d/YYYY)
PlantedRhi: Date when rhizomes were planted in the greenhouse (m/d/YYYY)
RhiID: Unique rhizome identifier
Treatment: (factor) Refers to the storage temperature at which rhizomes were stored for 14 days at 5 C (Control) and 25 C (reserve-depleted) for 14 days.
RhiInitialFW_g: Initial rhizome weight in grams when rhizomes were placed in storage.
SamplingDate: Date when plants were sampled for biomass, photosynthesis, and rhizome respiration and leaf area data (m/d/YYYY)
Phase: Refers to whether the measurement was collected during the storage period (Storage) or after planting (Growth)
RhiResp_ug.g.min: Rhizome respiration rate measured during the storage phase at the two different storage treatment (micro g CO2 / g rhizome / min)
Tair: Air temperature inside the respiration chamber used to measure rhizome respiration (Celsius).
Glucose_Rhi: Glucose content in the rhizome on a mass basis (%)
Glucose_Leaf: Glucose content in the leaf on a mass basis (%)
Sucrose_Rhi: Sucrose content, as glucose equivalents, in the rhizome on a mass basis (%)
Sucrose_Leaf: Sucrose content, as glucose equivalents, in the leaf on a mass basis (%)
Starch_Rhi: Starch content, as glucose equivalents, in the rhizome on a mass basis (%)
Starch_Leaf: Starch content, as glucose equivalents, in the leaf on a mass basis (%)
TotalGlu_Rhi: Total amount of glucose equivalents in the rhizome, as the sum of Glucose_Rhi, Sucrose_Rhi and Starch_Rhi.
TotalGlu_Leaf: Total amount of glucose equivalents in the leaf, as the sum of Glucose_Rhi, Sucrose_Rhi and Starch_Rhi.
Leaf.Area_cm2: Total leaf area of the plant, sum of leaves and stems.
AboveGround_g: Aboveground biomass of the plant after material was dried for 48hr at 60 C (g).
RhiSample_g: Rhizome fresh weight (g)
Root_g: Root biomass after material was dried for 48hr at 60 C (g).
Qin: Photosynthetic Photon Flux Density inside the cuvette used to measure photosynthesis.
A: net CO2 assimilation (mol CO2 m-2 s-1)
gsw: Stomatal conductance to water (mol H2O m-2 s-1)
PhiPS2: Quantum efficiency of photosystem II
NumberOfTiller: number of tillers per pot
totLeaves: Number of leaves per pot
Caputd: did the plant die during the experiment before being harvested? Yes (Dead), no (Alive)
In all columns, NA represents not available data. Usually caused by not all variables measured at all sampling dates.
Sharing/Access information
Companion manuscript is submitted to the Global Change Biology Bioenergy for publication.
Please direct correspondence to Mauricio Tejera-Nieves (mauri@msu.edu)
Code/Software
We used R (R Core Team, 2017) for all analyses and plots. We used lm() to fit linear models, gnls() in the nlme package to fir nonlinear models (Pinherio & Bates, 2000), and emmeans() in the emmeans package (Lenth, Singmann, Love, Buerkner, & Herve, 2018) for mean and parameter comparisons.
Scripts are available at: https://github.com/PerennialDr/SinkDepletion.
Please reach out to Mauricio Tejera-Nieves (mauri@msu.edu) for questions.
Methods
Rhizomes used in this experiment were harvested from a 12-year-old switchgrass stand in the Michigan State University Agronomy Farm (42.713 N, -84.467 W) in East Lansing, Michigan, USA. Rhizomes were harvested during winter, in early January, and stored at 5 °C for two weeks before the start of the reserve-depletion treatment. Reserve-depletion was imposed by storing switchgrass rhizomes at 25 °C for 14 days, control treatment rhizomes remained at 5 °C for the same period.
Immediately after the storage period, rhizomes were planted individually in 2.54 L pots filled with a peat and perlite mix (SureMixTM; Michigan Grower Products, Galesburg, MI, USA) and kept in a greenhouse at 27 °C and 16hr photoperiod supplemented with artificial lights for the length of the growth cycle (~180 days). Rhizome respiration, development, and photosynthesis were measured repeatedly over the course of the experiment. These non-destructive measurements were taken on randomly assigned rhizomes weekly or biweekly. Leaf net CO2 assimilation rate and stomatal conductance to water were measured biweekly in the middle portion of the youngest fully expanded leaf with a Li-6800.
Aboveground biomass, rhizome and root biomass, and total leaf area were sampled 5 times during the experiment. Rhizome biomass was also sampled three times during the storage period on the first, 8th and 14th day of storage. These destructive measurements were taken on 10 randomly preassigned rhizomes per treatment every 30 – 40 days.
To harvest belowground tissues, soil was rinsed using tap water and roots were removed from rhizomes. Roots were dried and weighted separately as with aboveground biomass. All rhizome samples were weighed fresh, placed in an aluminum pouch and flash frozen in liquid nitrogen for glucose, sucrose, and starch content analyses. Total belowground biomass was estimated as the sum of root and rhizome biomass.
Leaf and rhizome samples were stored at -80°C until further processing. Leaf samples were ground to a fine powder with a mortar and pestle. Rhizome samples were ground with a spice mixer (Cuisinart; SG-10). All samples stayed in contact with liquid nitrogen during grinding and were then freeze-dried for at least 48 hours in a lyophilizer. Leaf and rhizome starch, sucrose and free glucose were measured at the Biomass Analytics Facility at Michigan State University.
Usage notes
We used R (R Core Team, 2017) for all analyses and plots. We used lm() to fit linear models, gnls() in the nlme package to fir nonlinear models (Pinherio & Bates, 2000), and emmeans() in the emmeans package (Lenth, Singmann, Love, Buerkner, & Herve, 2018) for mean and parameter comparisons.
Code for data analysis and plotting can be found at: https://github.com/PerennialDr/SinkDepletion