Effects of nitrogen addition on photosynthetic characteristics of Leymus chinensis in the temperate grassland of Nei Mongol, China

doi:10.17521/cjpe.2016.0128

Abstract

Abstract:

Aims The increased atmospheric nitrogen (N) deposition due to human activity and climate change greatly causes grassland ecosystems shifting from being naturally N-limited to N-eutrophic or N-saturated, and further affecting the growth of grass species. The aims of this study are: 1) to evaluate the effects of different N addition levels on morphology and photosynthetic characteristics of Leymus chinensis; 2) to determine the critical N level to facilitate L. chinensis growth.
Methods We conducted a different N addition levels experiment in dominant species in the temperate steppe of Nei Mongol. The aboveground biomass, morphological and leaf physiological traits, pigment contents, chlorophyll a fluorescence parameters and biochemical parameters of L. chinensis were investigated.
Important findings Our results showed that aboveground biomass first increased and then decreased with the increased N, having the highest values at the 10 g N·m^-2·a^?1 treatment, but the 25 g N·m^-2·a^?1 still significantly increased the aboveground biomass relative to 0 g N·m^-2·a^?1. Leymus chinensis accommodate low N situation through allocating less N to carboxylation system and decreasing leaf mass per area (LMA) in order to get more light energy. Moderate N addition captured more light energy through increasing total chlorophyll (Chl) contents and decreasing the ratio of Chl a/b. Moderate N addition increased LMA, carboxylation efficiency, maximum carboxylation rate (V_cmax), maximum electron transport rate (J_max) and decreased J_max/V_cmax, thus allocating more N to carboxylation system to enhance carboxylation capability. Moreover, the photochemical activity of PSII was increased through higher effective quantum yield of PSII photochemistry, electron transport rate and photochemical quenching coefficient. Excessive N addition had negative effects on physiological variables of L. chinensis due to lower carboxylation capability and photochemical activity of PSII, further leading to decreased net photosynthetic rate, whereas increased non-photochemical quenching coefficient and carotenoids played the role in the dissipation of excess excitation energy. Overall, moderate N addition facilitated the photosynthetic characteristics of dominant species, but excessive N addition inhibited photosynthetic characteristics. The most appropriate N addition for the growth of L. chinensis was 5-10 g N·m^-2·a^?1in the temperate steppe of Nei Mongol, China.

http://jtp.cnki.net/bilingual/detail/html/ZWSB201702005

Key words: nitrogen addition, temperate grassland, Leymus chinensis, photosynthetic characteristics, photo- synthetic pigments

Zhan-Wei ZHAI, Ji-Rui GONG, Qin-Pu LUO, Yan PAN, Taogetao BAOYIN, Sha XU, Min LIU, Li-Li YANG. Effects of nitrogen addition on photosynthetic characteristics of Leymus chinensis in the temperate grassland of Nei Mongol, China[J]. Chin J Plant Ecol, 2017, 41(2): 196-208.

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URL: https://www.plant-ecology.com/EN/10.17521/cjpe.2016.0128

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Figures/Tables 8

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氮处理 N treatment	最大光化学量子产量 F_v/F_m	实际光化学量子产量 Ф_PSII	电子传递速率 ETR (μmol·m^-2·s^-1)	光化学淬灭系数 q_P	非光化学淬灭系数 NPQ
CK	0.81 ± 0.002^c	0.23 ± 0.001^a	153.0 ± 0.82^a	0.54 ± 0.002^b	2.63 ± 0.05^c
N1	0.80 ± 0.001^c	0.23 ± 0.003^a	156.9 ± 2.02^a	0.55 ± 0.003^ab	3.08 ± 0.05^a
N2	0.82 ± 0.002^a	0.23 ± 0.004^a	157.0 ± 2.80^a	0.59 ± 0.010^a	3.11 ± 0.05^a
N3	0.82 ± 0.002^ab	0.24 ± 0.009^a	161.9 ± 6.18^a	0.54 ± 0.008^b	2.82 ± 0.05^b
N4	0.81 ± 0.004^c	0.19 ± 0.010^b	127.3 ± 6.77^b	0.46 ± 0.016^c	2.74 ± 0.09^bc
N5	0.81 ± 0.003^abc	0.17 ± 0.003^b	117.0 ± 1.62^b	0.44 ± 0.004^c	2.79 ± 0.05^bc

氮处理 N treatment	最大光化学量子产量 F_v/F_m	实际光化学量子产量 Ф_PSII	电子传递速率 ETR (μmol·m^-2·s^-1)	光化学淬灭系数 q_P	非光化学淬灭系数 NPQ
CK	0.81 ± 0.002^c	0.23 ± 0.001^a	153.0 ± 0.82^a	0.54 ± 0.002^b	2.63 ± 0.05^c
N1	0.80 ± 0.001^c	0.23 ± 0.003^a	156.9 ± 2.02^a	0.55 ± 0.003^ab	3.08 ± 0.05^a
N2	0.82 ± 0.002^a	0.23 ± 0.004^a	157.0 ± 2.80^a	0.59 ± 0.010^a	3.11 ± 0.05^a
N3	0.82 ± 0.002^ab	0.24 ± 0.009^a	161.9 ± 6.18^a	0.54 ± 0.008^b	2.82 ± 0.05^b
N4	0.81 ± 0.004^c	0.19 ± 0.010^b	127.3 ± 6.77^b	0.46 ± 0.016^c	2.74 ± 0.09^bc
N5	0.81 ± 0.003^abc	0.17 ± 0.003^b	117.0 ± 1.62^b	0.44 ± 0.004^c	2.79 ± 0.05^bc

氮处理 N treatment	初始羧化效率 CE (mol·m^-2·s^-1)	最大羧化速率 V_cmax (μmol·m^-2·s^-1)	最大电子传递速率 J_max (μmol·m^-2·s^-1)	J_max/V_cmax
CK	0.005 ± 0.000 2^f	16.83 ± 0.49^e	16.48 ± 0.48^e	0.98 ± 0.03^b
N1	0.015 ± 0.000 4^d	26.14 ± 0.75^d	26.79 ± 0.77^d	1.02 ± 0.03^ab
N2	0.018 ± 0.000 5^c	22.98 ± 0.66^d	24.79 ± 0.72^d	1.08 ± 0.03^a
N3	0.045 ± 0.001 3^a	54.79 ± 1.58^a	47.80 ± 1.38^a	0.87 ± 0.03^c
N4	0.030 ± 0.000 9^b	40.18 ± 1.16^c	31.69 ± 0.91^c	0.79 ± 0.02^d
N5	0.010 ± 0.000 3^e	47.73 ± 1.38^b	36.80 ± 1.06^b	0.77 ± 0.02^d

氮处理 N treatment	初始羧化效率 CE (mol·m^-2·s^-1)	最大羧化速率 V_cmax (μmol·m^-2·s^-1)	最大电子传递速率 J_max (μmol·m^-2·s^-1)	J_max/V_cmax
CK	0.005 ± 0.000 2^f	16.83 ± 0.49^e	16.48 ± 0.48^e	0.98 ± 0.03^b
N1	0.015 ± 0.000 4^d	26.14 ± 0.75^d	26.79 ± 0.77^d	1.02 ± 0.03^ab
N2	0.018 ± 0.000 5^c	22.98 ± 0.66^d	24.79 ± 0.72^d	1.08 ± 0.03^a
N3	0.045 ± 0.001 3^a	54.79 ± 1.58^a	47.80 ± 1.38^a	0.87 ± 0.03^c
N4	0.030 ± 0.000 9^b	40.18 ± 1.16^c	31.69 ± 0.91^c	0.79 ± 0.02^d
N5	0.010 ± 0.000 3^e	47.73 ± 1.38^b	36.80 ± 1.06^b	0.77 ± 0.02^d