College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, China.
PLoS One. 2021 Feb 17;16(2):e0246944. doi: 10.1371/journal.pone.0246944. eCollection 2021.
Phosphorus (P) is an essential macronutrient for plant growth, development and production. However, little is known about the effects of P deficiency on nutrient absorption, photosynthetic apparatus performance and antioxidant metabolism in citrus. Seedlings of 'sour pummelo' (Citrus grandis) were irrigated with a nutrient solution containing 0.2 mM (Control) or 0 mM (P deficiency) KH2PO4 until saturated every other day for 16 weeks. P deficiency significantly decreased the dry weight (DW) of leaves and stems, and increased the root/shoot ratio in C. grandis but did not affect the DW of roots. The decreased DW of leaves and stems might be induced by the decreased chlorophyll (Chl) contents and CO2 assimilation in P deficient seedlings. P deficiency heterogeneously affected the nutrient contents of leaves, stems and roots. The analysis of Chl a fluorescence transients showed that P deficiency impaired electron transport from the donor side of photosystem II (PSII) to the end acceptor side of PSI, which showed a greater impact on the performance of the donor side of PSII than that of the acceptor side of PSII and photosystem I (PSI). P deficiency increased the contents of ascorbate (ASC), H2O2 and malondialdehyde (MDA) as well as the activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR) and glutathione reductase (GR) in leaves. In contrast, P deficiency increased the ASC content, reduced the glutathione (GSH) content and the activities of SOD, CAT, APX and monodehydroascorbate reductase (MDHAR), but did not increase H2O2 production, anthocyanins and MDA content in roots. Taking these results together, we conclude that P deficiency affects nutrient absorption and lowers photosynthetic performance, leading to ROS production, which might be a crucial cause of the inhibited growth of C. grandis.
磷（P）是植物生长、发育和生产的必需大量营养素。然而，对于缺磷对柑橘养分吸收、光合器官性能和抗氧化代谢的影响知之甚少。用含有 0.2 mM（对照）或 0 mM（缺磷）KH2PO4 的营养液每隔一天灌溉‘酸柚’（Citrus grandis）幼苗，直至饱和，共 16 周。缺磷显著降低了 C. grandis 叶片和茎的干重（DW），增加了根/茎比，但不影响根的 DW。叶片和茎 DW 的减少可能是由缺磷幼苗中叶绿素（Chl）含量和 CO2 同化的减少引起的。缺磷不均匀地影响叶片、茎和根的养分含量。Chl a 荧光瞬变分析表明，缺磷损害了从 PSII 供体侧到 PSI 末端受体侧的电子传递，这对 PSII 供体侧的性能影响大于对 PSI 和 PSI 受体侧的影响。缺磷增加了 ASC、H2O2 和丙二醛（MDA）的含量，以及叶片中超氧化物歧化酶（SOD）、过氧化氢酶（CAT）、抗坏血酸过氧化物酶（APX）、脱氢抗坏血酸还原酶（DHAR）和谷胱甘肽还原酶（GR）的活性。相比之下，缺磷增加了 ASC 含量，降低了 GSH 含量以及 SOD、CAT、APX 和单脱氢抗坏血酸还原酶（MDHAR）的活性，但没有增加 H2O2 的产生、根中的花青素和 MDA 含量。综上所述，我们得出结论，缺磷影响养分吸收并降低光合作用性能，导致 ROS 产生，这可能是 C. grandis 生长受到抑制的关键原因。
