Wang Feng, Gao Jingwen, Yong Jean W H, Wang Qiang, Ma Junwei, He Xinhua
Institute of Environmental Resources, Soil and Fertilizer, Zhejiang Academy of Agricultural Sciences, Hangzhou, China.
Centre of Excellence for Soil Biology, College of Resources and Environment, Southwest University, Chongqing, China.
Front Plant Sci. 2020 Dec 2;11:537443. doi: 10.3389/fpls.2020.537443. eCollection 2020.
Photosynthesis of wheat and maize declined when grown with NH as a nitrogen (N) source at ambient CO concentration compared to those grown with a mixture of NO and NH , or NO as the sole N source. Interestingly, these N nutritional physiological responses changed when the atmospheric CO concentration increases. We studied the photosynthetic responses of wheat and maize growing with various N forms at three levels of growth CO levels. Hydroponic experiments were carried out using a C plant (wheat, L. cv. Chuanmai 58) and a C plant (maize, L. cv. Zhongdan 808) given three types of N nutrition: sole NO (NN), sole NH (AN) and a mixture of both NO and NH (Mix-N). The test plants were grown using custom-built chambers where a continuous and desired atmospheric CO ( ) concentration could be maintained: 280 μmol mol (representing the pre-Industrial Revolution CO concentration of the 18th century), 400 μmol mol (present level) and 550 μmol mol (representing the anticipated futuristic concentration in 2050). Under AN, the decrease in net photosynthetic rate ( ) was attributed to a reduction in the maximum RuBP-regeneration rate, which then caused reductions in the maximum Rubisco-carboxylation rates for both species. Decreases in electron transport rate, reduction of electron flux to the photosynthetic carbon [] and electron flux for photorespiratory carbon oxidation [] were also observed under AN for both species. However, the intercellular ( ) and chloroplast ( ) CO concentration increased with increasing atmospheric CO in C wheat but not in C maize, leading to a higher ratio. Interestingly, the reduction of under AN was relieved in wheat through higher CO levels, but that was not the case in maize. In conclusion, elevating atmospheric CO concentration increased and in wheat, but not in maize, with enhanced electron fluxes towards photosynthesis, rather than photorespiration, thereby relieving the inhibition of photosynthesis under AN. Our results contributed to a better understanding of NH involvement in N nutrition of crops growing under different levels of CO.
与以硝酸盐和铵盐混合物或仅以硝酸盐作为氮源种植的小麦和玉米相比，在环境二氧化碳浓度下以铵盐作为氮源种植时，小麦和玉米的光合作用下降。有趣的是，当大气二氧化碳浓度增加时，这些氮营养生理反应会发生变化。我们研究了在三种生长二氧化碳水平下，以不同氮形态生长的小麦和玉米的光合反应。使用一种C3植物（小麦，Triticum aestivum L. cv. Chuanmai 58）和一种C4植物（玉米，Zea mays L. cv. Zhongdan 808）进行水培实验，给予三种类型的氮营养：仅硝酸盐（NN）、仅铵盐（AN）以及硝酸盐和铵盐的混合物（混合氮）。测试植物在定制的培养箱中生长，在其中可以维持连续且所需的大气二氧化碳（CO₂）浓度：280 μmol mol⁻¹（代表18世纪工业革命前的二氧化碳浓度）、400 μmol mol⁻¹（当前水平）和550 μmol mol⁻¹（代表2050年预期的未来浓度）。在铵盐处理下，净光合速率（Pn）的下降归因于最大核酮糖-1,5-二磷酸（RuBP）再生速率的降低，这进而导致两个物种的最大羧化酶（Rubisco）羧化速率降低。在铵盐处理下，两个物种还观察到电子传递速率降低、光合碳[C]的电子通量减少以及光呼吸碳氧化[O]的电子通量减少。然而，C3小麦的细胞间（Ci）和叶绿体（Cc）二氧化碳浓度随着大气二氧化碳增加而增加，但C4玉米则不然，导致更高的Ci/Ca比率。有趣的是，在较高二氧化碳水平下，铵盐处理下小麦的Pn降低得到缓解，但玉米并非如此。总之，提高大气二氧化碳浓度增加了小麦的Pn和羧化效率（CE），但玉米没有，增强了朝向光合作用而非光呼吸的电子通量，从而缓解了铵盐处理下对光合作用的抑制。我们的结果有助于更好地理解铵盐在不同二氧化碳水平下生长的作物氮营养中的作用。
