甘蔗叶片光合CO2响应参数分析及其品种间差异

甘蔗光合作用的CO2响应是甘蔗生理生态研究的重要内容。作为C4植物的甘蔗具有较高的光合效率，是最重要的糖料作物。为比较不同模型拟合甘蔗CO2响应曲线的效果，分析不同品种甘蔗光合CO2响应特性，探究甘蔗光合CO2响应参数之间的关系，本文使用LI-6400XT光合测定系统在云南开远进行了田间观测，用直角双曲线模型（RH）、非直角双曲线模型（NRH）、叶子飘（Ye）模型拟合6个品种甘蔗光合CO2响应曲线，并分析光合CO2响应参数。结果表明：RH和NRH模型拟合的最大光合速率（Amax）偏差较大，且无法得到CO2饱和点（CSP）。NRH模型拟合的初始羧化速率（η）与实测值最为接近，但得到的呼吸速率（Rp）和CO2补偿点（CCP）均为负。综合来看叶子飘模型模拟甘蔗叶片光合CO2响应的效果最佳。Ye模型得到的光合CO2响应参数中，η与Rp/CCP呈极显著正相关（P<0.01），Rp与η、CCP呈显著正相关（P<0.05），Rp、η与CSP呈显著负相关（P<0.05）。有的品种在低CO2浓度时表现高光合特性，伴随高呼吸消耗，同时在高浓度CO2时光合能力较弱，易达到CO2饱和点。Ye模型得到的6个品种甘蔗的Amax平均值为32.44.5mol·m-2·s-1，η平均值为0.1280.060，CSP平均值为115277mol·m-2·s-1，CCP平均值为8.55.5mol·m-2·s-1。品种ROC22具有很低的Rp、CCP和最高的Amax，光合特性最好；除YZ99-91外其它5个品种甘蔗的CSP都较大，能适应大气中CO2浓度的升高。

Sugarcane Leaf Photosynthetic CO2 Responses Parameters and Their Difference among Varieties

Sugarcane (Saccharum officinarum L.)photosynthetic CO2 response represents an important physiological characteristic for sugarcane growth. Sugarcane is the major sugar crop, exhibiting the characteristic of higher photosynthetic efficiency as a C4 plant. This study was conducted to compare performance of different models of photosynthetic CO2 response, and to investigate the photosynthetic CO2 response characteristics of different sugarcane varieties. Field measurements were carried out in Kaiyuan, Yunnan Province, using a portable LI-6400XT photosynthesis system to explore the correlation between the photosynthetic CO2 response parameters. The non-rectangular hyperbola model (NRH), rectangular hyperbola model (RH) and Ye model were used to fit the sugarcane photosynthetic CO2 response curve of six varieties, and the photosynthetic CO2 response parameters were analyzed. The results showed that the photosynthetic CO2 response curve fitted by NRH and RH model do not determine CO2 saturation point (CSP), and overestimate the maximum net photosynthetic rate (Amax). The initial carboxylation rate (η) fitted by NRH model were almost the same as the measured values, but the respiration rate (Rp) and CO2 compensation point (CCP) fitted by NRH model were both negative. In general, the Ye model was the best in simulating the photosynthetic CO2 response curves. In the photosynthetic CO2 response parameters fitted by Ye model, η was significantly correlated (positively) with Rp/CCP (P<0.001), Rp was significantly correlated (positively) with η and CCP (P<0.05), η and Rp were significantly correlated (negatively) with CSP (P<0.05). The varieties with higher photosynthetic rate under low CO2 concentration tended to have higher respiration rate, meanwhile, they have lower photosynthesis capacity under high CO2 concentration, which are easier to reach CO2 saturation point. The average Amax value of six sugarcane varieties fitted by Ye model was 32.44.5mol·m-2·s-1, η was 0.1280.060, CSP was 115277mol·m-2·s-1 and CCP was 8.55.5045mol·m-2·s-1. ROC22 had lower Rp, and CCP and the highest Amax, indicating the most realistic to represent photosynthetic characteristics. All the five sugarcane varieties except YZ99-91 have large CSP, and could adapt to the increasing CO2 concentration in the atmosphere.