Elevated atmospheric CO2 and drought effects on leaf gas exchange properties of barley

Atmospheric CO₂ concentration (C_a) is rising, predicted to cause global warming, and alter precipitation patterns. During 1994, spring barley (Hordeum vulgare L. cv. Alexis) was grown in a strip-split-plot experimental design to determine the effects that the main plot C_a treatments [A: Ambient at 370 μmol (CO₂) mol⁻¹; E: Enriched with free-air CO₂ enrichment (FACE) at ∼550 μmol (CO₂) mol⁻¹] had on several gas exchange properties of fully expanded sunlit primary leaves. The interacting strip-split-plot irrigation treatments were Dry or Wet [50% (D) or 100% (W) replacement of potential evapotranspiration] at ample nitrogen (261 kg N ha⁻¹) and phosphorous (29 kg P ha⁻¹) fertility. Elevated C_a facilitated drought avoidance by reducing stomatal conductance (g_s) by 34% that conserved water and enabled stomata to remain open for a longer period into a drought. This resulted in a 28% reduction in drought-induced midafternoon depression in net assimilation rate (A). Elevated C_a increased A by 37% under Dry and 23% under Wet. Any reduction in A under Wet conditions occurred because of nonstomatal limitations, whereas under Dry it occurred because of stomatal limitations. Elevated C_a increased the diurnal integral of A (A′) that resulted in an increase in the seasonal-long integral of A′ (A″) for barley leaves by 12% (P = 0.14) under both Dry and Wet - 650, 730, 905 and 1020 ± 65 g (C) m⁻² y⁻¹ for AD, ED, AW and EW treatments, respectively. Elevated C_a increased season-long average dry weight (DW_S; crown, shoots) by 14% (P = 0.02), whereas deficit irrigation reduced DW_S by 7% (P = 0.06), although these values may have been affected by a short but severe pea aphid [Acyrthosiphon pisum (Harris)] infestation. Hence, an elevated-C_a-based improvement in gas exchange properties enhanced growth of a barley crop.     

麻疯树成熟胚乳再生植株及其气孔分析

对麻疯树成熟胚乳进行组织培养获得胚乳再生植株,并对其气孔进行分析.麻疯树成熟胚乳在25℃、12 h光照条件下培养7 d愈伤组织诱导完成,2,4-D浓度为2.0 mg L-1的MS培养基愈伤诱导效果最好,诱导率达89.29%.愈伤组织在含BAP的改良培养基上培养至黄绿色后转入分化培养基,在含IAA 0.25 mg L-1和ZT 1.5 mg L-1的WPM培养基上不定芽分化率达32.50%.将分化的不定芽从愈伤组织上剥离后转入含IBA、BAP和GA3的培养基上进行芽伸长培养.取胚乳不定芽叶片接种在含IBA 0.1 mg L-1、BAP 0.5 mg L-1和TDZ 0.5 mg L-1的MS培养基上诱导生芽后,再转入含IAA 0.25mgL-1、KT 0.5mg L-1、BAP 1.0 mg L-1和GA3 0.25 mg L-1的培养基上进行丛生芽的诱导,成芽率为85.2%.这些芽在含0.1 mgL-1 IBA的1/2 MS培养基上生根,大约有37.5%的芽生了根,平均有5.2条根系形成.与母本植株相比,再生的胚乳植株保卫细胞更大,且气孔密度减小.图2表6参24     

湿地生态系统CO2净交换、水汽通量及二者关系浅析

湿地生态系统碳循环是陆地碳循环研究中的重要组成部分,对于全球变化具有重要意义。水汽通量是影响湿地生态系统碳循环最重要、最基本的生态因子之一,与湿地生态系统CO2净交换密切相关。本文在总结湿地生态系统CO2净交换与水汽通量变化基本规律及其主要影响因子的基础上,从宏观和微观2个方面分析二者之间的内在关系。从宏观上看,湿地生态系统本身的特点决定了CO2净交换与水汽通量之间必然是相互影响、相互制约的;就微观而言,叶片尺度上的气孔行为是水分蒸腾和净碳通量这两个生理生态过程相互联系的纽带。最后,对湿地生态系统CO2净交换与水汽通量关系的研究方向提出展望。     

盐胁迫对油菜幼苗生长和光合特征的影响

采用盆栽砂培试验,研究了不同浓度(0、50、100、200、300mmol·L-1)NaCl胁迫10和30d对油菜(Brassica napus)幼苗干质量、叶绿素(Chl)含量、净光合速率(Pn)、气孔导度(Gs)、细胞间CO2浓度(xi)、蒸腾速率(Rt)、水分利用效率(Ew,u)和气孔限制值(Ls)等的影响.结果表明,在NaCl胁迫下,油菜幼苗植株干质量显著降低,长期高盐胁迫下油菜干质量降低更显著;随NaCl浓度的增加,Chl含量、Chl a/Chl b比值均呈先升高后降低的变化趋势,处理10d,Chl含量、Chl a/Chl b比值在NaCl浓度为200mmol·L-1条件下达最大值,处理30d,在NaCl浓度为100mmol·L-1条件下达最大值.在50～100mmol·L-1NaCl胁迫下,油菜叶片的Pn、xi和Ls所受影响均很小;高盐胁迫下,其Pn、Gs、xi和Rt均显著下降,而Ew,u和Ls则显著上升.相关分析显示,植株干质量与Chl含量、Chl a/Chl b比值间无相关性,与Na+、Cl-含量,Ew,u和Ls间呈显著负相关(P＜0.01),与根冠比,K+、Ca2+含量,K+/Na+、Ca2+/Na+比值,K+与Na+的选择性比率[S(K+,Na+)],Ca2+与Na+的选择性比率[S(Ca2+,Na+)],Pn,Gs,xi和Rt间呈显著正相关(P＜0.01).上述结果表明,200mmol·L-1 NaCl胁迫10和30d、300mmol·L-1 NaCl胁迫10d,油菜幼苗光合抑制主要来自气孔限制,而300mmol·L-1 NaCl胁迫30d,气孔限制和非气孔限制在油菜幼苗光合抑制中均具有重要作用.Na+、Cl-、K+、Ca2+含量,Ew,u,Ls,根冠比,K+/Na+、Ca2+/Na+比值,S(K+,Na+),S(Ca2+,Na+),Pn,Gs,xi和Rt均可作为油菜生长盐适应性的评价指标.