18O enrichment of leaf cellulose correlated with 18O enrichment of leaf sucrose but not bulk leaf water in a C3 grass across contrasts of atmospheric CO2 concentration and air humidity
18O enrichment of leaf cellulose correlated with 18O enrichment of leaf sucrose but not bulk leaf water in a C3 grass across contrasts of atmospheric CO2 concentration and air humidity
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DOI：
10.21203/rs.3.rs-596094/v1
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发表时间：
2021-06
期刊：
影响因子：
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通讯作者：
J. C. B. Cabrera;R. Hirl;R. Schäufele;Jianjun Zhu;Haitao Liu;J. Ogée;H. Schnyder
中科院分区：
文献类型：
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作者：
J. C. B. Cabrera;R. Hirl;R. Schäufele;Jianjun Zhu;Haitao Liu;J. Ogée;H. Schnyder
植物纤维素的18 O组成通常用于重建过去的气候和植物功能。然而，关于叶片蔗糖18 O信号的估计及其随后在纤维素合成过程中与源水交换18 O的衰减仍然存在不确定性。·研究了不同CO2浓度（200、400和800 mmol mol-1）和相对湿度（50%和75%）条件下多年生黑麦草（Lolium perenne）叶片中蔗糖（Δ 18 OSucrose）、叶片含水量（Δ 18 OLW）、叶片纤维素（Δ 18 OCellulose）和纤维素合成部位含水量（Δ 18 OCelSynW）的18 O富集情况。· Δ 18 O纤维素与Δ 18 O蔗糖相关（R2=0.87），但与Δ 18 OLW无关（R2=0.04），这是由于蔗糖合成水（Δ 18 OSucSynW，由Δ 18 O蔗糖估算）和大量叶片水之间的可变18 O差异（范围为2.0-9.0‰）。这种差异主要是由于相对湿度的影响。在纤维素形成过程中与介质水交换的纤维素中的氧的比例（pex）当参考Δ 18 OSucSynW时接近恒定（pex-SucSynW = 0.52±0.02 SE），但当与大量叶水相关时变化（pex-LW = -0.01至0.46）。·我们得出结论，先前报道的禾本科植物中pex-LW的RH依赖性变化与Δ 18 OSucSynW和Δ 18 OLW之间的差异有关，这可能是由于叶片水分和光合蔗糖合成的18 O梯度的空间异质性造成的。
· The 18O composition of plant cellulose is often used to reconstruct past climate and plant function. However, uncertainty remains regarding the estimation of the leaf sucrose 18O signal and its subsequent attenuation by 18O exchange with source water during cellulose synthesis.· We grew Lolium perenne at three CO2 concentrations (200, 400 or 800 mmol mol-1) and two relative humidity (RH) levels (50% or 75%), and determined 18O enrichment of leaf sucrose (Δ18OSucrose), bulk leaf water (Δ18OLW), leaf cellulose (Δ18OCellulose) and water at the site of cellulose synthesis (Δ18OCelSynW). · Δ18OCellulose correlated with Δ18OSucrose (R2=0.87) but not with Δ18OLW (R2=0.04), due to a variable 18O discrepancy (range 2.0-9.0‰) between sucrose synthesis water (Δ18OSucSynW, estimated from Δ18OSucrose) and bulk leaf water. The discrepancy resulted mainly from an RH effect. The proportion of oxygen in cellulose that exchanged with medium water during cellulose formation (pex), was near-constant when referenced to Δ18OSucSynW (pex-SucSynW = 0.52±0.02 SE), but varied when related to bulk leaf water (pex-LW = –0.01 to 0.46). · We conclude that previously reported RH-dependent variations of pex-LW in grasses are related to a discrepancy between Δ18OSucSynW and Δ18OLW that may result from spatial heterogeneity in 18O gradients of leaf water and photosynthetic sucrose synthesis.