Zhou Gaofeng, Fu Yiping, Yang Mei, Li Yanhong, Zhang Jing
National Navel Orange Engineering Research Center, College of Navel Orange, Gannan Normal University, Ganzhou 341000, China.
International Education School, Gannan Normal University, Ganzhou 341000, China.
Plants (Basel). 2025 Jan 8;14(2):158. doi: 10.3390/plants14020158.
Roots play essential roles in the acquisition of water and minerals from soils in higher plants. However, water or nutrient limitation can alter plant root morphology. To clarify the spatial distribution characteristics of essential nutrients in citrus roots and the influence mechanism of micronutrient deficiency on citrus root morphology and architecture, especially the effects on lateral root (LR) growth and development, two commonly used citrus rootstocks, trifoliate orange ( L. Raf., Ptr) and red tangerine ( Blanco, Cre), were employed here. The analysis of the mineral nutrient distribution characteristics in different root parts showed that, except for the P concentrations in Ptr, the last two LR levels (second and third LRs) had the highest macronutrient concentrations. All micronutrient concentrations in the second and third LRs of Ptr were higher than those of Cre, except for the Zn concentration in the second LR, which indicates that Ptr requires more micronutrients to maintain normal root system growth and development. Principal component analysis (PCA) showed that B and P were very close in terms of spatial distribution and that Mo, Mn, Cu, and Fe contributed significantly to PC1, while B, Cu, Mo, and Zn contributed significantly to PC2 in both rootstocks. These results suggest that micronutrients are major factors in citrus root growth and development. The analysis of root morphology under micronutrient deficiency showed that root growth was more significantly inhibited in Ptr and Cre under Fe deficiency (FeD) than under other micronutrient deficiencies, while Cre roots exhibited better performance than Ptr roots. From the perspective of micronutrient deficiency, FeD and B deficiency (BD) inhibited all root morphological traits in Ptr and Cre except the average root diameter, while Mn deficiency (MnD) and Zn deficiency (ZnD) had lesser impacts, as well as the morphology of the stem. The mineral nutrient concentrations in Ptr and Cre seedlings under micronutrient deficiency revealed that single micronutrient deficiencies affected both their own concentrations and the concentrations of other mineral nutrients, whether in the roots or in stems and leaves. Dynamic analysis of LR development revealed that there were no significant decreases in either the first or second LR number in Ptr seedlings under BD and ZnD stress. Moreover, the growth rates of first and second LRs in Ptr and Cre did not significantly decrease compared with the control under short-term (10 days) BD stress. Altogether, these results indicate that micronutrients play essential roles in citrus root growth and development. Moreover, citrus alters its root morphology and biological traits as a nutrient acquisition strategy to maintain maximal micronutrient acquisition and growth. The present work on the spatial distribution characteristics and micronutrient deficiency of citrus roots provides a theoretical basis for effective micronutrient fertilization and the diagnosis of micronutrient deficiency in citrus.
在高等植物中，根系在从土壤中获取水分和矿物质方面发挥着重要作用。然而，水分或养分限制会改变植物根系形态。为了阐明柑橘根系中必需养分的空间分布特征以及微量养分缺乏对柑橘根系形态和结构的影响机制，特别是对侧根（LR）生长发育的影响，本研究采用了两种常用的柑橘砧木，枳（Poncirus trifoliata (L.) Raf., Ptr）和红橘（Citrus reticulata Blanco, Cre）。对不同根系部位矿质养分分布特征的分析表明，除枳中磷的浓度外，最后两级侧根（第二级和第三级侧根）的大量养分浓度最高。枳第二级和第三级侧根中的所有微量养分浓度均高于红橘，除了第二级侧根中的锌浓度，这表明枳需要更多的微量养分来维持正常的根系生长发育。主成分分析（PCA）表明，在两种砧木中，硼和磷在空间分布上非常接近，而钼、锰、铜和铁对主成分1有显著贡献，硼、铜、钼和锌对主成分2有显著贡献。这些结果表明，微量养分是柑橘根系生长发育的主要因素。对微量养分缺乏条件下根系形态进行分析，结果表明，缺铁（FeD）条件下，枳和红橘的根系生长受到的抑制比其他微量养分缺乏条件下更显著，而红橘根系表现优于枳根系。从微量养分缺乏的角度来看，缺铁和缺硼（BD）抑制了枳和红橘除平均根径外的所有根系形态特征，而缺锰（MnD）和缺锌（ZnD）的影响较小，对地上部形态也有影响。微量养分缺乏条件下枳和红橘幼苗的矿质养分浓度表明，单一微量养分缺乏会影响其自身浓度以及其他矿质养分的浓度，无论是在根系中还是在茎叶中。对侧根发育的动态分析表明，在缺硼和缺锌胁迫下，枳幼苗的第一级或第二级侧根数量均无显著减少。此外，在短期（10天）缺硼胁迫下，枳和红橘第一级和第二级侧根的生长速率与对照相比没有显著降低。总之，这些结果表明微量养分在柑橘根系生长发育中起重要作用。此外，柑橘通过改变其根系形态和生物学特性作为一种养分获取策略，以维持最大程度的微量养分获取和生长。目前关于柑橘根系空间分布特征和微量养分缺乏的研究为柑橘有效施用微量养分肥料和诊断微量养分缺乏提供了理论依据。
