Lou Yuanxin, Wang Ruolan, Che Peiyue, Zhao Chuan, Chen Yali, Yang Yangheshan, Mu Junpeng
Ecological Security and Protection Key Laboratory of Sichuan Province, Mianyang Normal University, Mianyang 621000, China.
Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, China.
Biology (Basel). 2023 Aug 14;12(8):1132. doi: 10.3390/biology12081132.
The variability observed in the annual seed production of perennial plants can be seen as an indication of changes in the allocation of resources between growth and reproduction, which can be attributed to fluctuations in the environment. However, a significant knowledge gap exists concerning the impacts of nitrogen addition on the interannual seed production patterns of perennial plants. We hypothesized that the addition of nitrogen would impact the annual variations in the seed production of perennial plants, ultimately affecting their overall reproductive efficiency. A multiyear field experiment was conducted to investigate the effects of varying nitrogen supply levels (e.g., 0, 4, and 8 kg N ha yr of N0, N4, and N8) on vegetative and floral traits, pollinator visitation rates, and seed traits over a period of four consecutive years. The results showed that the N0 treatment exhibited the highest levels of seed production and reproductive efficiency within the initial two years. In contrast, the N4 treatment displayed its highest level of performance in these metrics in the second and third years, whereas the N8 treatment showcased its most favorable outcomes in the third and fourth years. Similar patterns were found in the number of flowers per capitulum and the number of capitula per plant. There exists a positive correlation between aboveground biomass and several factors, including the number of flowers per capitulum, the number of capitula per plant, the volume of nectar per capitulum, and the seed production per plant. A positive correlation was found between pollinator visitation and the number of flowers per capitulum or the number of capitula per plant. This implies that the addition of N affected the maintenance of plant aboveground biomass, flower trait stability, pollinator visitation, and, subsequently, the frequency of seed production and reproductive efficiency. Our results suggest that augmenting the nitrogen content in the soil may have the capacity to modify the inherent variability in seed production that is observed across various years and enhance the effectiveness of reproductive processes. These findings have the potential to enhance our comprehension of the impact of nitrogen addition on the reproductive performance of perennial herbaceous plants and the underlying mechanisms of biodiversity in the context of global environmental changes.
多年生植物年度种子产量的变化可被视为生长和繁殖之间资源分配变化的一个指标，这可能归因于环境波动。然而，关于添加氮对多年生植物年际种子生产模式的影响，存在显著的知识空白。我们假设添加氮会影响多年生植物种子产量的年度变化，最终影响其整体繁殖效率。进行了一项多年田间试验，以研究连续四年不同氮供应水平（如分别为0、4和8千克氮/公顷·年的N0、N4和N8）对营养和花部性状、传粉者访花率以及种子性状的影响。结果表明，在最初两年内，N0处理的种子产量和繁殖效率最高。相比之下，N4处理在第二年和第三年这些指标上表现出最高水平，而N8处理在第三年和第四年展示出最有利的结果。在每头状花序的花朵数量和每株植物的头状花序数量上也发现了类似模式。地上生物量与几个因素之间存在正相关，包括每头状花序的花朵数量、每株植物的头状花序数量、每头状花序的花蜜量以及每株植物的种子产量。传粉者访花与每头状花序的花朵数量或每株植物的头状花序数量之间存在正相关。这意味着添加氮影响了植物地上生物量的维持、花部性状稳定性、传粉者访花，进而影响了种子生产频率和繁殖效率。我们的结果表明，增加土壤中的氮含量可能有能力改变多年间观察到的种子生产固有变异性，并提高繁殖过程的有效性。这些发现有可能增进我们对添加氮对多年生草本植物繁殖性能的影响以及全球环境变化背景下生物多样性潜在机制的理解。
