Leaf internal diffusion conductance limits photosynthesis more strongly in older leaves of Mediterranean evergreen broad-leaved species
Leaf internal diffusion conductance limits photosynthesis more strongly in older leaves of Mediterranean evergreen broad-leaved species
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DOI：
10.1111/j.1365-3040.2005.01392.x
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发表时间：
2005-12-01
影响因子：
7.3
通讯作者：
Tosens, T
中科院分区：
文献类型：
--
作者：
Niinemets, Ü;Cescatti, A;Tosens, T
研究了Laurus nobilis L.、Olea europea L.和Quercus ilex L.的成熟非衰老叶片的结构、氮含量、内部叶肉扩散电导(g(m))、光合电子传递能力(J(max))和Rubisco最大羧化酶活性(V-cmax)与年龄相关的变化，以检验光合作用生化和扩散限制的相对显着性随叶龄变化的假设。 L. nobilis 和 O. europea 的叶子寿命可达 3 年，Q. ilex 的叶子寿命可达 6 年。叶龄的增加导致所有物种的单位面积叶片干质量（MA）增加，叶片干鲜质量比增大，单位干质量氮含量（N-M）降低，而冬青和冬青的单位面积氮含量（N-A）降低。较老的叶子具有较低的 g(m)、J(max) 和 V-cmax 由于 M-A 随年龄而增加，基于质量的 g(m)、J(max) 和 V-cmax 随着年龄的增长比基于面积（5 至 7 倍）的特征下降得更强烈（7 至 10 倍）。扩散电导与叶片光合潜力呈正相关。然而，这种相关性是曲线的，导致叶绿体与内部 CO2 浓度的比率 (C-c/C-i) 较低，并且在 g(m) 较低的老叶中，CO2 从叶片内部空气空间到叶绿体的下降量较大 (Delta(c))。总体而言，年龄依赖性的光合潜力下降与光合蛋白中 N-M 和 N 分数的下降有关，而 gm 的下降与 MA 和细胞壁分数的增加有关。这些与年龄相关的修饰改变了叶子光合潜力与 M-A、N-M 和 N-A 的功能缩放。这些物种的差异主要在于叶子结构和功能特征随年龄变化的变化率，以及各种变量随年龄变化的程度。气孔开放度与叶龄相关性较弱，但由于气孔开放度的物种差异，气孔和叶肉之间的总扩散限制在物种之间的分布存在差异。这些数据共同表明，在地中海常绿植物中，光合作用的结构限制与生化限制强烈相互作用。在这些物种中，gm 和光合能力的年龄依赖性变化不会以协调的方式发生，因此叶肉扩散限制对老叶的光合作用的抑制作用比对新叶的抑制更大。
Leaf age-dependent changes in structure, nitrogen content, internal mesophyll diffusion conductance (g(m)), the capacity for photosynthetic electron transport (J(max)) and the maximum carboxylase activity of Rubisco (V-cmax) were investigated in mature non-senescent leaves of Laurus nobilis L., Olea europea L. and Quercus ilex L. to test the hypothesis that the relative significance of biochemical and diffusion limitations of photosynthesis changes with leaf age. The leaf life-span was up to 3 years in L. nobilis and O. europea and 6 years in Q. ilex. Increases in leaf age resulted in enhanced leaf dry mass per unit area (MA), larger leaf dry to fresh mass ratio, and lower nitrogen contents per dry mass (N-M) in all species, and lower nitrogen contents per area (N-A) in L. nobilis and Q. ilex. Older leaves had lower g(m), J(max) and V-cmax Due to the age-dependent increase in M-A, mass-based g(m), J(max) and V-cmax declined more strongly (7- to 10-fold) with age than area-based (5- to 7-fold) characteristics. Diffusion conductance was positively associated with foliage photosynthetic potentials. However, this correlation was curvilinear, leading to lower ratio of chloroplastic to internal CO2 concentration (C-c/C-i) and larger drawdown Of CO2 from leaf internal air space to chloroplasts (Delta(c)) in older leaves with lower g(m). Overall the age-dependent decreases in photosynthetic potentials were associated with decreases in N-M and in the fraction of N in photosynthetic proteins, whereas decreases in gm were associated with increases in MA and the fraction of cell walls. These age-dependent modifications altered the functional scaling of foliage photosynthetic potentials with M-A, N-M, and N-A. The species primarily differed in the rate of age-dependent modifications in foliage structural and functional characteristics, but also in the degree of age-dependent changes in various variables. Stomatal openness was weakly associated with leaf age, but due to species differences in stomatal openness, the distribution of total diffusion limitation between stomata and mesophyll varied among species. These data collectively demonstrate that in Mediterranean evergreens, structural limitations of photosynthesis strongly interact with biochemical limitations. Age-dependent changes in gm and photosynthetic capacities do not occur in a co-ordinated manner in these species such that mesophyll diffusion constraints curb photosynthesis more in older than in younger leaves.