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首页> 外文期刊>Journal of Experimental Botany >Shade compromises the photosynthetic efficiency of NADP-ME less than that of PEP-CK and NAD-ME C-4 grasses
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Shade compromises the photosynthetic efficiency of NADP-ME less than that of PEP-CK and NAD-ME C-4 grasses

机译：遮阳损害了nadp-me的光合效率低于pep-ck和nad-me c-4草的光合效率

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摘要

The high energy cost and apparently low plasticity of C-4 photosynthesis compared with C-3 photosynthesis may limit the productivity and distribution of C-4 plants in low light (LL) environments. C-4 photosynthesis evolved numerous times, but it remains unclear how different biochemical subtypes perform under LL. We grew eight C-4 grasses belonging to three biochemical subtypes [NADP-malic enzyme (NADP-ME), NAD-malic enzyme (NAD-ME), and phosphoenolpyruvate carboxykinase (PEP-CK)] under shade (16% sunlight) or control (full sunlight) conditions and measured their photosynthetic characteristics at both low and high light. We show for the first time that LL (during measurement or growth) compromised the CO2 -concentrating mechanism (CCM) to a greater extent in NAD-ME than in PEP-CK or NADP-ME C-4 grasses by virtue of a greater increase in carbon isotope discrimination (Delta p) and bundle sheath CO2 leakiness (phi), and a greater reduction in photosynthetic quantum yield (Phi(max)). These responses were partly explained by changes in the ratios of phosphoenolpyruvate carboxylase (PEPC)/initial Rubisco activity and dark respiration/photosynthesis (R-d/A). Shade induced a greater photosynthetic acclimation in NAD-ME than in NADP-ME and PEP-CK species due to a greater Rubisco deactivation. Shade also reduced plant dry mass to a greater extent in NAD-ME and PEP-CK relative to NADP-ME grasses. In conclusion, LL compromised the co-ordination of the C-4 and C-3 cycles and, hence, the efficiency of the CCM to a greater extent in NAD-ME than in PEP-CK species, while CCM efficiency was less impacted by LL in NADP-ME species. Consequently, NADP-ME species are more efficient at LL, which could explain their agronomic and ecological dominance relative to other C-4 grasses.
机译：与C-3光合作用相比，C-4光合作用的高能量成本和明显低可塑性可能限制低光（LL）环境中C-4植物的生产率和分布。 C-4光合作用众多次数发展，但仍然不明确不同的生物化学亚型在LL下表现。在阴影（16％阳光）或阳光下）或控制（完全阳光）条件，并在低光和高光下测量它们的光合特性。我们首次表明LL（在测量或增长期间）在NAD-ME更大程度上损害了CO2-复合机制（CCM），而不是PEP-CK或NADP-ME C-4草，凭借更大的增加在碳同位素辨别（Delta P）和束鞘CO2泄漏（PHI）中，以及光合量子产率的更大降低（PHI（MAX））。部分反应部分解释了磷酸丙酮酸羧化酶（Pepc）/初始Rubisco活性和暗呼吸/光合作用（R-D / A）的比例的变化。由于更高的Rubisco失活，阴影在NAD-ME中诱导了较大的光合作用灌注序列，而不是在NADP-ME和PEP-CK物种中。在NADP-ME草相对于NADP-ME草地上，遮阳也将植物干肿块降低到NAD-ME和PEP-CK。总之，LL损害了C-4和C-3循环的协调，因此，CCM在NAD-ME中的效率比PEP-CK物种在更大程度上，而CCM效率则影响较小在NADP-ME物种中。因此，NADP-ME物种在LL更高效，这可以解释他们相对于其他C-4草的农艺和生态优势。

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