平茬措施对天然沙冬青生理特性的影响

沙冬青(Ammopiptanthus mongolicus(Maxim.)Cheng f.)是我国二级珍稀濒危植物,由于自然条件的不断恶化使这一古老残遗物种种群受到威胁。本文以西鄂尔多斯国家级自然保护区内生长的天然沙冬青为材料,对平茬后经过3年恢复生长的萌蘖灌丛和未平茬的沙冬青灌丛的地上部生物量、叶片相对含水量(RWC)、叶水势(WPB)、净光合速率(Pn)、蒸腾速率(Tr)、水分利用效率(WUE)、气孔导度(Gs)和胞间CO2浓度(Ci)等指标进行了测定,并对平茬处理的各项生理指标变化进行了研究。结果显示:平茬后的沙冬青萌蘖灌丛经过3年的生长能恢复到平茬前的生物量;平茬与未平茬(对照)沙冬青叶片相对含水量差异不显著(P0.05),但平茬后的沙冬青叶水势日间(7∶00-19∶00)均显著高于对照(P0.05);平茬与未平茬沙冬青日间净光合速率、蒸腾速率均出现两个高峰值,且均有"午休"现象,平茬后的沙冬青萌蘖丛Pn日均值比对照升高了15.73%、Tr日均值比对照升高了15.57%、WUE日均值比对照升高了13.92%(P0.05);Gs日均值比对照也有所上升,且与Pn、Tr的变化趋势基本一致,但Ci的变化趋势与Gs、Pn和Tr相反。说明平茬处理对增加地上部生物量、提高其生理指标均有明显作用,能提高沙冬青潜在的生产力。

Effect of Stubble Treatment on the Physiological Characteristics of Ammopiptanthus mongolicus

Ammopiptanthus mongolicus (Maxim.) Cheng f. is a Chinese secondary rare and endangered plant. The continuous deterioration of the natural environment of the Western Ordos Plateau National Nature Reserve threatens populations of this plant. A mechanical stubble measure was conducted as a treatment. Physiological characteristics such as leaf relative water content (RWC), leaf water potential (WPB), net photosynthetic rate (Pn), transpiration rate (Tr), water utilization efficiency (WUE), stomatal conductance (Gs) and intercellular CO₂ concentration (Ci) were measured. Results showed that the biomass of A. mongolicus could completely return to pre-stubble level after three years of growth. There was no significant difference (P > 0.05) in relative water content of leaves between stubble and non-stubble, but leaf water potential and water use efficiency (WUE) were significantly different (P < 0.05). The leaf water potential of stubble treatment was significantly higher than that of non-stubble treatment. The diurnal change in the photosynthetic and transpiration rates between these two different treatments presented as typical "twin peak" curves and they showed an obvious "lunch break" phenomenon. The stubble treatment exhibited 15.73%, 15.57%, 13.92% higher Pn, Tr and WUE, than that of non-stubble treatment, respectively. Gs of the stubble treatment was the same as Pn and Tr, but Ci was completely different. This indicated that stubble treatment for A. mongolicus had obvious advantages in growth and physiological characteristics and improved productivity potential.