胡杨异胚发育叶片碳平衡研究

胡杨成熟个体植株上的叶片可大概分为3种叶形,即阔卵圆形(BO)、过渡形(O)及披针形(L).叶片尺度的碳平衡取决于光合作用和呼吸作用,但机理尚不明.作者研究了胡杨异形叶的气体交换、形态学和生化特性.结果显示:① 胡杨3种叶形比叶面积(SLA)存在显著差异,阔卵圆形叶比叶面积SLA=(6.69±0.24)m2·kg-1显著低于其余两者(过渡形叶SLA=(7.36±0.09)m2·kg-1,披针形叶SLA=(8.09±0.16)m2·kg-1),叶片单位质量氮含量(Nmass)存在差异但不具显著差异;② 阔卵圆形叶单位面积碳同化速率(Aarea=(11.92±1.22)μmol·m-2·s-1)显著高于过渡形叶(Aarea=(10.21±1.43)μmol·m-2·s-1)和披针形叶(Aarea=(9.98±1.04)μmol·m-2·s-1),然而,单位质量(Amass)和单位氮碳同化速率(AN)在3种叶形中并不具显著差异,披针形叶的Amass=(80.37±7.07)μmol·kg-1·s-1(DW)和AN=(80.37±7.07)μmol·kg-1·s-1(DW)略高于其它2种叶形;③ 阔卵圆形叶单位面积及单位质量暗呼吸速率(Rn-area=(1.90±0.17)μmol·m-2·s-1和Rn-mass=(12.58±0.77)μmol·kg-1·s-1(DW))显著高于过渡形叶(Rn-area=(1.60±0.19)μmol·m-2·s-1和Rn-mass=(11.85±0.15)μmol·kg-1·s-1(DW))及披针形叶(Rn-area=(1.57±0.29)μmol·m-2·s-1和Rn-mass=(11.25±0.92)μmol·kg-1·s-1(DW)),另外,3种叶形叶片光下线粒体呼吸速率(RL)均大于暗呼吸速率,说明光对暗呼吸有抑制作用,且不同叶形抑制程度也不同,从披针叶形50.37%到阔卵圆形叶的80.67%;④ 不同叶形叶片水平碳平衡(Ag/R)差异不显著,但披针形叶的Ag/R=7.90±1.39高于其余2种叶形(阔卵圆形叶Ag/R=6.19±0.87,过渡形叶Ag/R=7.65±1.71).由此推测,阔卵圆形叶片可能具更强结构支持能力和更高呼吸速率,利于个体的生理维持,而披针形叶具更高的碳同化能力则用于支持生长.

A study on the carbon balance of the heteromorphic leave of Populus euphratica

Desert poplar(Populus euphratica) is known as a heteroblastic species,with the leaves of mature individuals being roughly classified into three types,namely broad ovate leaf(BO),lanceolate leaf(L) and ovate leaf(O).Previous studies have shown that polymorphic leaves of Populus euphratica differs in their anatomical and physiological properties.The leaf level carbon balance which is determined by both photosynthesis and respiration,however,remains is unclear.Gas exchange characteristics,morphological and biochemical traits of polymorphic leaves of Populus euphratica were studied.Our results showed:(a) Specific leaf area differed(SLA) among polymorphic leaves,with the SLA being significantly higher for ovate leaf(SLA=(7.36±0.09)m2·kg-1) and lanceolate leaf(SLA=(8.09±0.16)m2·kg-1) than for broad ovate leaf(SLA=(6.69±0.24)m2·kg-1).Leaf nitrogen content marginally varied among leaves of different shapes but was not statistically significant;(b) Area-based leaf carbon assimilation rate(Aarea) of broad ovate leaf(Aarea=(11.92±1.22)μmol·m-2·s-1) was significantly higher than that of ovate leaf(Aarea=(10.21±1.43)μmol·m-2·s-1) and lanceolate leaf(Aarea=(9.98±1.04)μmol·m-2·s-1).However,mass-based(Amass) and nitrogen-based carbon assimilation rate(AN) did not differ among polymorphic leaves,with the Amass and AN even being slightly higher for lanceolate leaf(Amass=(80.37±7.07)μmol·kg-1·DW·s-1 and AN=(80.37±7.07)μmol·kg-1·DW·s-1) than for other leaf types;(c) Broad ovate leaf showed a significantly greater dark respiration rate on both area and mass basis(Rn-area=(1.90±0.17)μmol·m-2·s-1 and Rn-mass=(12.58±0.77)μmol·kg-1·DW·s-1) than that of ovate leaf(Rn-area=(1.60±0.19)μmol·m-2·s-1 and Rn-mass=(11.85±0.15)μmol·kg-1·DW·s-1)and lanceolate leaf(Rn-area=(1.57±0.29)μmol·m-2·s-1 and Rn-mass=(11.25±0.92)μmol·kg-1·DW·s-1).Furthermore,mitochondrial respiration taking place under daylight(RL) was consistently lower than Rn,reflecting the occurrence of light inhibition of dark respiration.Moreover,the inhibitory effect of light on dark respiration varied among leaf types,spanning from 50.37% in lanceolate leaf to 80.67% in broad ovate leaf;(d) Leaf level carbon balance(Ag/R) did not differe among leaf types,with Ag/R ratio being higher for lanceolate leaf(Ag/R=7.90±1.39) than for broad ovate leaf(Ag/R=6.19±0.87) and ovate leaf(Ag/R=7.65±1.71).Additionally,Ag/Rn was invariably lower than Ag/RL due to the inhibitory effect of light on dark respiration.It is concluded that broad ovate leaves with high physical rigidity and respiration rate may be of importance for individual maintenance,while lanceolate leaves with high carbon gain ability are predominant in supporting growth.