Abstract
All over the world, a common problem in the soil is the low content of available zinc (Zn), which is unevenly distributed and difficult to move. However, information on the foraging strategies of roots in response to heterogeneous Zn supply is still very limited. Few studies have analyzed the adaptability of maize inbred lines with different Zn efficiencies to different low Zn stress time lengths in maize. This study analyzed the effects of different time lengths of low Zn stress on various related traits in different inbred lines. In addition, morphological plasticity of roots and the response of Zn-related important gene iron-regulated transporter-like proteins (ZIPs) were studied via simulating the heterogeneity of Zn nutrition in the soil. In this report, when Zn deficiency stress duration was extended (from 14 to 21 days), under Zn-deficient supply (0.5 μM), Zn efficiency (ZE) based on shoot dry weight of Wu312 displayed no significant difference, and ZE for Ye478 was increased by 92.9%. Under longer-term Zn deficiency, shoot, and root dry weights of Ye478 were 6.5 and 2.1-fold higher than those of Wu312, respectively. Uneven Zn supply strongly inhibited the development of some root traits in the -Zn region. Difference in shoot dry weights between Wu312 and Ye478 was larger in T1 (1.97 times) than in T2 (1.53 times). Under heterogeneous condition of Zn supply, both the –Zn region and the +Zn region upregulated the expressions of ZmZIP3, ZmZIP4, ZmZIP5, ZmZIP7, and ZmZIP8 in the roots of two inbred lines. These results indicate that extended time length of low-Zn stress will enlarge the difference of multiple physiological traits, especially biomass, between Zn-sensitive and Zn-tolerant inbred lines. There were significant genotypic differences of root morphology in response to heterogeneous Zn supply. Compared with split-supply with +Zn/+Zn, the difference of above-ground biomass between Zn-sensitive and Zn-tolerant inbred lines under split-supply with –Zn/+Zn was higher. Under the condition of heterogeneous Zn supply, several ZmZIP genes may play important roles in tolerance to low Zn stress, which can provide a basis for further functional characterization.
Highlights
Zinc (Zn) is an essential micronutrient in plant growth and development
Except for the treatment without Zn supply, Zn use efficiency of Wu312 was higher than that of Ye478 (Figure 4J). These findings showed that Zn uptake efficiency of maize plants decreased more, and Zn use efficiency increased more under longer-term Zn-deficiency stress
Heterogeneous Zn supply induced higher expression of both ZmZIP5 and ZmZIP7 in the Differences in Physiological Responses of Seedling Maize to Different Zn Stress Levels and Stress Time Lengths In Experiment 1, shoot dry weight of Ye478 under Zn-deficient condition (0.5 μM) was 1.5 times higher than that of Wu312 despite there being no significant difference in root dry weight between two inbred lines (Figures 2A,B)
Summary
Zinc (Zn) is an essential micronutrient in plant growth and development. It plays an important role in various enzymatic reactions, metabolic processes, redox reactions, plant hormone metabolism, promoting the development of plant reproductive organs, resistance to infection by certain pathogens, and improving plant resistance to stress (Shemi et al, 2021; Suganya et al, 2021). Because of the adsorption and fixation of calcium carbonate, organic matter, phosphate, and clay in the soil, the effectiveness of Zn in the soil is low (Cakmak, 2008). The lack of Zn in the soil leads to lower yields (Aziz et al, 2017), and affects nutritional quality of crop plants (Cakmak and Kutman, 2018). Zn deficiency in plants causes damage to plant cells mainly at the cell membrane level (Candan et al, 2018) and can alter mitochondrial ultrastructure (Chen et al, 2009)
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