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Scientia Silvae Sinicae ›› 2016, Vol. 52 ›› Issue (5): 55-63.doi: 10.11707/j.1001-7488.20160507

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Response of Photosynthesis and Nitrogen Distribution of Torreya grandis ‘Merrilli’ Seedlings in Different Light Regimes

Song Yang1, Liao Liang2, Liu Tao3, Jiang Yanfeng4, Yu Weiwu1, Hu Yuanyuan1, Wu Jiasheng1   

  1. 1. The Nurturing Station for Key Laboratory of Subtropical Silviculture Zhejiang Agriculture and Forestry University Li'an 311300;
    2. Yandang Forest Farms of Yueqing City Yueqing 325614;
    3. Hangzhou Raw Seed Growing Farm Yuhang 311115;
    4. Lishui Forestry Institute of Zhejiang Lishui 323000
  • Received:2015-11-10 Revised:2016-01-14 Online:2016-05-25 Published:2016-06-01

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Abstract:

[Objective] To elucidate the mechanism of photosynthetic characteristics and nitrogen allocation of Torreya grandis ‘Merrilli’ seedlings under different shading levels, the growth, gas exchanges parameters, chlorophyll content and leaf nitrogen content were measured. [Method] We measured the height, ground diameter, biomass, light response curve, CO2 response curve, chlorophyll content, leaf nitrogen content of T. grandis ‘Merrilli’ seedlings under different shading levels(0%, 50%, 75% and 90%). [Result] The results showed that the leaf color of seedlings became much greener with the increasing level of shade levels. However, the diameter increment and biomass of seedlings showed an increase at first, followed by a decreased trend with increasing shade level. The seedlings at 50% and 75% shade levels had the greatest diameter increment, which was 215.2% and 233.6% of that at 0% shade level and 161.4% and 175.2% of that at 90% shade level, respectively. The biomass at 75% shade level was significanly higher than the other shade treatments, and was 141.0%, 111.5% and 114.0% compared with that at 0%, 50% and 90% shade level respectively. The root/shoot ratio of seedlings reduced gradually, while the chlorophyll a (Chl a), chlorophyll b (Chl b) and carotenoid (Car) content increased with increasing of shade levels. LCP (light compensation point), and LSP (light saturation point) decreased while the apparent quantum efficiency (AQY) increased with increasing of shade level. Maximum net photosynthetic rate (Pmax), maximum RuBP carboxylation rate (Vcmax) and RuBP regeneration of photosynthetic electron transport rate (Jmax) showed an increase at first, followed by a decreased trend with increasing of shade level and the highest parameters were observed at 50% and 75% shade levels. However, the leaf nitrogen content per unit area (Na) showed a decrease trend with increasing of shade level. Moreover, the fraction of leaf nitrogen allocated to carboxylation (NC), the fraction of leaf nitrogen allocated to bioenergetics (NB), the fraction of leaf nitrogen allocated to light-absorbing pigment (NL), and photosynthetic nitrogen utilization efficiency (PNUE) showed a decrease trend with increasing of shade levels, and the highest values of these parameters except NL were observed at 75% shade level. [Conclusion] Shade treatment can effectively promote the growth of T. grandis ‘Merrilli’ seedlings. The seedlings grown under shade treatment can effectively use the lower light intensity at early morning or late afternoon in comparison to that grown at full sun light. Heavy shading (90% shading level) significantly decreased the Pmax, which may be related to the capacity to capture more light, and thus more resources were used to the light protein, resulting in a decline in photosynthetic capacity. Compared with the 50% shade level, the 75% shade level had more nitrogen allocated to the photosynthetic mechanism, such as in Nc and NB, and significant higher PNUE. Thus, our results indicate that T. grandis ‘Merrilli’ seedlings likely grow better at 75% shade level for seedling cultivation.

Key words: Torreya grandis ‘Merrilli’, biomass, photosynthetic characteristics, leaf nitrogen content, photosynthetic nitrogen utilization efficiency

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