迁地保护的4种龙脑香冠层叶光合速率和叶绿素荧光参数的日变化

doi:10.17521/cjpe.2005.0130

摘要/Abstract

摘要：

龙脑香科植物是东南亚热带雨林冠层的优势树种,在生态和经济上具有重要地位,而我国西南地区被认为是龙脑香科植物分布的最北端。该文于2004年雨季测定了西双版纳热带植物园迁地保护区内引种的4种国产龙脑香科植物:望天树(Parashorea chinensis)、云南龙脑香(Dipterocarpus retusus)、版纳青梅(Vatica xishuangbannaensis)和海南坡垒(Hopea hainanensis)冠层叶片的光响应曲线、光合速率的日进程、叶绿素荧光参数、叶绿素含量及叶片平均面积、气孔保卫细胞长度和分布状况等。结果表明,4种植物的最大光合速率(P_max)(7.5~18.1 μmol·m ^-2·s^-1,用单位叶面积表示;89.1~150.8 nmol·g^-1 DW·s^-1,用单位干重表示)、暗呼吸速率(R_d)、光补偿点(LSP)、光饱和点(LCP)、表观量子效率和叶片特征差异显著。在正午时4个树种均出现光合作用显著降低的现象,其中海南坡垒光合速率下降最少。虽然高的叶片温度对光合作用有一定的影响,但正午光合作用的下降主要是由于正午高的叶片-空气的水蒸气压力差(LAVPD)引起的气孔关闭造成的。4个树种正午的光系统Ⅱ线性电子传递的量子效率Φ_PSⅡ显著降低,表明遭受了强烈的光抑制。云南龙脑香、版纳青梅和海南坡垒的非光化学猝灭系数(NPQ)在正午时升高的幅度最大,而望天树的NPQ上升较少,表明热耗散是前3个树种的主要光保护机制。中午前后望天树的表观电子传递速率(ETR)一直保持在很高的水平,但其光合速率显著降低,表明大量的电子被分配到光呼吸上,也说明望天树主要通过光呼吸来保护光合机构。

关键词: 冠层叶, 叶绿素荧光, 龙脑香科, 日进程, 光合作用

Abstract:

Dipterocarps dominate the canopy of tropical rainforest of Southeast Asia. They are not only the world's main source of hardwood timber, but their canopy leaves are main organs for global carbon sequestration. Due to anthropogenic activities, many species of dipterocarps are threatened. Because of this situation, ex-situ conservation efforts were employed to conserve the genetic resources of several dipterocarps.
In this study, four dipterocarp species, Dipterocarpus retusus, Hopea hainanensis, Parashorea chinensis (emergent tree species in the rainforest) and Vatica xishuangbannaensis, were selected as study species that had been transplanted in 1981 to an ex-situ dipterocarp conservation forest in Xishuangbanna Tropical Botanical Garden. We measured the diurnal changes in photosynthetic rates, parameters of chlorophyll fluorescence, and morphological traits of their canopy leaves at 15-21 m height during the rainy season of 2004. The results indicated that the maximum photosynthetic rates (P_max) per unit leaf area (7.5 to 18.1 μmol·m ^-2·s^-1) and mass (89.08 to 150.82 nmol·g^-1 DW·s^-1), dark respiration rates (R_d), light saturation point (LSP), light compensation point (LCP) and leaf morphological traits differed significantly among species. Photosynthesis in the four species was depressed at midday. The results revealed that stomatal closure induced by high leaf-to-air vapor pressure deficit (LAVPD) led to photosynthetic depression at midday. Quantum yields of photosystem II (Φ_PSⅡ) in four dipterocarp species decreased significantly at midday, indicating that photoinhibition occurred. However, their PSⅡ values recovered to the early morning value by sunset, indicating that photoinhibition was reversible. The nonphotochemical quenching rate (NPQ) increased significantly in D. retusus, H. hainanensis and V. xishuangbannaensis, indicating that NPQ was used mainly to dissipate excess light energy absorbed by PSⅡ. At midday, the electron transport rate (ETR) in P. chinensis was maintained at high levels, while its photosynthetic rate decreased, suggesting that a large proportion of electrons were allocated to photorespiration. Thus photorespiration was the main mechanism protecting the photosynthetic apparatuses of P. chinensis during the midday photosynthesis depression. Other parameters, such as leaf area, size and density of stomata, and total chlorophyll content, also were measured at the same time. There was a general ranking of P_max in the following order from highest to lowest: D. retusus, P. chinensis, H. hainanensi, V. xishuangbannaensis. Based on the diurnal changes in chlorophyll fluorescence, both leaf stomatal limitations and non-stomatal effects played an important role to prevent photodamage during the midday depression of photosynthesis brought by the high irradiances, high air temperature, low humidity, and so on. The high midday leaf water potential of the four species showed that water limitations had no influence on photosynthetic rates.

Key words: Canopy leaf, Chlorophyll fluorescence, Dipterocarpaceae, Diurnal change, Photosynthesis

孟令曾, 张教林, 曹坤芳, 许再富. 迁地保护的4种龙脑香冠层叶光合速率和叶绿素荧光参数的日变化. 植物生态学报, 2005, 29(6): 976-984. DOI: 10.17521/cjpe.2005.0130

MENG Ling-Zeng, ZHANG Jiao-Lin, CAO Kun-Fang, XU Zai-Fu. DIURNAL CHANGES OF PHOTOSYNTHETIC CHARACTERISTICS AND CHLOROPHYLL FLUORESCENCE IN CANOPY LEAVES OF FOUR DIPTOCARP SPECIES UNDER EX-SITU CONSERVATION. Chinese Journal of Plant Ecology, 2005, 29(6): 976-984. DOI: 10.17521/cjpe.2005.0130

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链接本文: https://www.plant-ecology.com/CN/10.17521/cjpe.2005.0130

https://www.plant-ecology.com/CN/Y2005/V29/I6/976

图/表 8

表1 4个树种的基本信息

Table 1 The general information of the four species selected

树种 Species	云南龙脑香 Dipterocarpus retusus	海南坡垒 Hopea hainanensis	望天树 Parashorea chinensis	版纳青梅 Vatica xishuangbannaensis
样木平均高度 Height of sampled trees (m)	21 (45)^*	18 (25)	17 (60)	15 (40)
样木平均胸径 DBH of sampled trees (cm)	25.3	22.3	19.0	14.0
中国分布地区和海拔 Regions and altitude distributed in China	云南盈江, 西藏墨脱(600~1 000 m) Yingjiang in Yunnan, Motuo in Tibet (600-1 000 m)	海南崖县、琼中(400~800 m) Yaxian, Qiongzhong in Hainan (400-800 m)	云南补蚌, 广西那坡 (700~950 m) Bubeng in Yunnan, Napo in Guangxi (700-950 m)	云南补蚌, 广西那坡 (800~1 100 m) Bubeng in Yunnan, Napo in Guangxi (800-1 100 m)

图1 4个树种冠层叶光合作用的光响应曲线 a: 以单位叶面积表示 On area basis b: 以单位干重表示 On mass basis ●云南龙脑香Dipterocarpus retusus ○望天树Parashorea chinensis ▲海南坡垒Hopea hainanensis ▽版纳青梅Vatica xishuangbannaensis 数据点为平均值±标准误 Data were means±SE (n=3-4) Pn: 净光合速率 Net photosynthesis rate PPFD: 光通量密度 Photon flux density

Fig.1 The light-photosynthetic response curves of canopy leaves in four species

表2 4个树种冠层叶片的气体交换参数

Table 2 Gas exchange parameters of the canopy leaves in four species

树种 Species	云南龙脑香 Dipterocarpus retusus	海南坡垒 Hopea hainanensis	望天树 Parashorea chinensis	版纳青梅 Vatica xishuangbannaensis
最大净光合速率 Maximal net photosynthetic rate (P_max)
以单位叶面积表示 On area basis (μmol·m^-2·s^-1)	18.10±1.13^a	14.43±0.52^b	12.97±0.93^b	7.50±0.59^c
以单位干重表示 On dry weight (nmol ·g ^-1 DW·s^-1)	140.10±16.93^a	101.79±2.52^b	150.82±11.32^a	89.08±8.27^b
暗呼吸速率 Dark respiration rate (R_d)
以单位叶面积表示 On area basis (μmol·m^-2·s^-1)	2.08±0.15^a	1.35±0.09^b	1.22±0.03^b	0.70±0.10^c
以单位干重表示 On dry weight (nmol ·g ^-1 DW·s^-1)	13.86±2.06^a	9.13±1.03^a	13.98±0.88^a	8.44±1.15^a
光饱和点 Light satuaration point (μmol·m^-2·s^-1)	791±93^b	1184±109^a	1311±204^a	851±81^b
光补偿点 Light compensation point (μmol·m^-2·s^-1)	15.8±0.9^b	30.4±2.6^a	10.3±2.0^b	11.6±1.8^b
表观量子效率 Apparent quantum yield (μmol·μmol^-1)	0.062±0.005^a	0.034±0.002^b	0.051±0.008^ab	0.031±0.003^b

图2 4个树种净光合速率、气孔导度、水分利用效率及环境参数的日变化 ●云南龙脑香Dipterocarpus retusus ○望天树Parashorea chinensis ▲海南坡垒Hopea hainanensis ▽版纳青梅Vatica xishuangbannaensis 数据点为平均值±标准误 Data were means±SE (n=3-4) Pn、PPFD: 同图1 See Fig.1 Gs: 气孔导度 Stomatal conductance WUE: 水分利用效率 Water use efficiency LAVPD: 叶片到空气的水气压差 Leaf-to-air vapor pressure deficit

Fig.2 The diurnal changes in net photosynthetic rate (Pn), stomatal conductance (Gs), water use efficiency (WUE) and environmental parameters of four dipterocarp species

图3 4个树种叶绿素荧光参数的日变化 ●云南龙脑香Dipterocarpus retusus ○望天树Parashorea chinensis ▲海南坡垒Hopea hainanensis ▽版纳青梅Vatica xishuangbannaensis 数据点为平均值±标准误 Data were means±SE (n=3-4) ΦPSⅡ: 光系统II下的光量子效率 Quantum yields of PSII NPQ: 非光化学猝灭 Nonphotochemical quenching rate ETR: 电子传递速率 Electron transport rate

Fig.3 The diurnal changes in parameters of chlorophyll fluorescence in four dipterocarp species

表3 4个树种冠层叶片的叶片水势、叶绿素含量和叶片特征

Table 3 Leaf water potential, chlorophyll content and leaf traits in four dipterocarp species

树种 Species	云南龙脑香 Dipterocarpus retusus	海南坡垒 Hopea hainanensis	望天树 Parashorea chinensis	版纳青梅 Vatica xishuangbannaensis
正午水势 Midday leaf water potential (MPa)	-0.058±0.003^b	-0.071±0.007^a	-0.094±0.012^a	-0.072±0.004^ab
相对含水量 Relative water content (%)	98.0±0.4^a	99.6±0.3^a	93.9±0.6^b	98.8±0.2^a
叶绿素含量 Total chl content (mg·g^-1 FW)	1.39±0.29^b	1.97±0.17^a	2.46±0.37^a	1.53±0.12^b
叶绿素a/b比值 Ratios of chl a/b	2.71±0.05^a	2.50±0.07^ab	2.20±0.17^b	2.61±0.08^a
比叶面积 Specific leaf area (cm²·g^-1)	76.85±5.02^b	72.23±2.70^b	116.65±7.20^a	118.40±2.90^a
气孔密度 Stomatal density (mm^-2)	89.5±1.79^c	90.0±0.19^c	105.2±1.89^b	158.6±1.79^a
保卫细胞长度 Guard cell length (μm)	25.41±0.69^a	22.10±0.47^b	21.96±0.23^b	19.77±0.50^c
平均叶面积 Average leaf area (cm²)	403.8±26.7^a	66.6±2.5^b	47.6±2.1^c	42.9±2.1^c

图4 4个树种净光合速率和气孔导度的相关性数据为一天的所有测定值 Data were pooled from all measurements during a day 在图a和b中黑点分别代表云南龙脑香和海南坡垒, 白点分别代表望天树和版纳青梅 Black dot represents Dipterocarpus retusus and Hopea hainanensis, white dot represents Parashorea chinensis and Vatica xishuangbannaensis 4个种的回归方程分别是 The regression equations of four species are Pn=50.74Gs-0.96 R2=0.77 p<0.001n=48 Dipterocarpus retusus Pn=58.14Gs+0.84 R2=0.72 p<0.001n=60 Parashorea chinensis Pn=46.33Gs+2.45 R2=0.79 p<0.001n=86 Hopea hainanensis Pn=37.88Gs+1.21 R2=0.63 p<0.001n=71 Vatica xishuangbannaensis Pn、Gs: 同图2 See Fig.2

Fig.4 The relationship between Pn and Gs in four dipterocarp species

图5 4个树种气孔导度和叶片水蒸气压差的相关性数据为一天的所有测定值 Data were pooled from all measurements during a day 在图a和b中黑点分别代表云南龙脑香和海南坡垒, 白点分别代表望天树和版纳青梅 Black dot represents Dipterocarpus retusus and Hopea hainanensis, white dot represents Parashorea chinensis and Vatica xishuangbannaensis 4个种的回归方程分别是 The regression equations of four species are Gs=-0.05LAVPD+0.27 R2=0.55 p<0.001n=48 Dipterocarpus retusus Gs=-0.03LAVPD+0.21 R2=0.39 p<0.001n=60 Parashorea chinensis Gs=-0.05LAVPD+0.28 R2=0.51 p<0.001n=86 Hopea hainanensis Gs=-0.05LAVPD+0.20 R2=0.37 p<0.001n=71Vatica xishuangbannaensis Gs、LAVPD: 同图2 See Fig.2

Fig.5 The relationship between LAVPD and Gs in four dipterocarp species

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