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Rapid Crown Root Development Confers Tolerance to Zinc Deficiency in Rice.

Nanda AK, Wissuwa M - Front Plant Sci (2016)

Bottom Line: Zinc (Zn) deficiency is one of the leading nutrient disorders in rice (Oryza sativa).We therefore conclude that the rate of crown root initiation was differentially affected by Zn deficiency between genotypes.Rapid crown root development, following transplanting, was identified as a main causative trait for tolerance to Zn deficiency and better Zn retranslocation from shoot to root was a key attribute of Zn-efficient genotypes.

View Article: PubMed Central - PubMed

Affiliation: Crop, Livestock and Environment Division, Japan International Research Center for Agricultural Sciences Tsukuba, Japan.

ABSTRACT
Zinc (Zn) deficiency is one of the leading nutrient disorders in rice (Oryza sativa). Many studies have identified Zn-efficient rice genotypes, but causal mechanisms for Zn deficiency tolerance remain poorly understood. Here, we report a detailed study of the impact of Zn deficiency on crown root development of rice genotypes, differing in their tolerance to this stress. Zn deficiency delayed crown root development and plant biomass accumulation in both Zn-efficient and inefficient genotypes, with the effects being much stronger in the latter. Zn-efficient genotypes had developed new crown roots as early as 3 days after transplanting (DAT) to a Zn deficient field and that was followed by a significant increase in total biomass by 7 DAT. Zn-inefficient genotypes developed few new crown roots and did not increase biomass during the first 7 days following transplanting. This correlated with Zn-efficient genotypes retranslocating a higher proportion of shoot-Zn to their roots, compared to Zn-inefficient genotypes. These latter genotypes were furthermore not efficient in utilizing the limited Zn for root development. Histological analyses indicated no anomalies in crown tissue of Zn-efficient or inefficient genotypes that would have suggested crown root emergence was impeded. We therefore conclude that the rate of crown root initiation was differentially affected by Zn deficiency between genotypes. Rapid crown root development, following transplanting, was identified as a main causative trait for tolerance to Zn deficiency and better Zn retranslocation from shoot to root was a key attribute of Zn-efficient genotypes.

No MeSH data available.


Related in: MedlinePlus

Zinc content and retranslocation of Nipponbare, Zn-efficient and inefficient genotypes growing in nutrient solution without Zn. Zn content in whole plants (A), Zn root to shoot ratio (B) and Zn content of shoot (C) and roots (D) before (0 WAT) and after (2 WAT) growth without Zn. Statistical significant differences (p < 0.05) are indicated by different letter for each group. Error bars represent SEM (n = 3 per genotype).
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Figure 3: Zinc content and retranslocation of Nipponbare, Zn-efficient and inefficient genotypes growing in nutrient solution without Zn. Zn content in whole plants (A), Zn root to shoot ratio (B) and Zn content of shoot (C) and roots (D) before (0 WAT) and after (2 WAT) growth without Zn. Statistical significant differences (p < 0.05) are indicated by different letter for each group. Error bars represent SEM (n = 3 per genotype).

Mentions: Nipponbare and Zn-efficient genotypes were capable of developing more roots than Zn-inefficient genotypes in the complete absence of an external source of Zn. In order to accomplish this, Nipponbare and Zn-efficient genotypes must contain more Zn, be capable of growing more roots per unit of Zn available, or retranslocating more Zn from other tissues to the roots, or all of the above. To investigate this, Zn content of Nipponbare, Zn-efficient and inefficient genotypes was measured in the seed (before sowing) and in the shoot and the roots at different time points. Seeds from Zn-inefficient genotypes contained 22% less Zn than seeds from Zn-efficient genotypes (Table 1, Supplementary Table S3). Nipponbare seeds also contained less Zn, compared to those of Zn-efficient genotypes, but only by 9% (Table 1). However, at 0 WAT, seedlings of all genotypes contained the same total amount of Zn in their shoot and roots, though its distribution was slightly different (Figures 3A,B and Supplementary Table S4). Zn-inefficient genotypes had a higher proportion of Zn in the roots, resulting in a higher root to shoot ratio (0.24) at 0 WAT, compared to the Zn-efficient genotypes (0.17) and Nipponbare (0.17; Figure 3B). At 2 WAT to Zn-free nutrient solution, no difference in total Zn content was observed for either Nipponbare, Zn-inefficient or efficient genotypes, confirming that no Zn uptake took place (Figure 3A). However, during the 2-week-growth period, 17% of shoot-Zn was retranslocated to roots in Zn-efficient plants, compared to only 11% in Zn-inefficient plants (Figure 3C). Impressively, Nipponbare retranslocated 25% of its shoot-Zn to roots. This resulted in an increase in root-Zn of 113% for Nipponbare and 109% for Zn-efficient genotypes, while the root-Zn of Zn-inefficient genotypes only increased by 41% (Figure 3D). As a result, the Zn root to shoot ratio of Nipponbare and Zn-efficient genotypes increased by 185 and 118%, respectively, while that of Zn-inefficient genotypes only increased by 60% (Figure 3B).


Rapid Crown Root Development Confers Tolerance to Zinc Deficiency in Rice.

Nanda AK, Wissuwa M - Front Plant Sci (2016)

Zinc content and retranslocation of Nipponbare, Zn-efficient and inefficient genotypes growing in nutrient solution without Zn. Zn content in whole plants (A), Zn root to shoot ratio (B) and Zn content of shoot (C) and roots (D) before (0 WAT) and after (2 WAT) growth without Zn. Statistical significant differences (p < 0.05) are indicated by different letter for each group. Error bars represent SEM (n = 3 per genotype).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4815024&req=5

Figure 3: Zinc content and retranslocation of Nipponbare, Zn-efficient and inefficient genotypes growing in nutrient solution without Zn. Zn content in whole plants (A), Zn root to shoot ratio (B) and Zn content of shoot (C) and roots (D) before (0 WAT) and after (2 WAT) growth without Zn. Statistical significant differences (p < 0.05) are indicated by different letter for each group. Error bars represent SEM (n = 3 per genotype).
Mentions: Nipponbare and Zn-efficient genotypes were capable of developing more roots than Zn-inefficient genotypes in the complete absence of an external source of Zn. In order to accomplish this, Nipponbare and Zn-efficient genotypes must contain more Zn, be capable of growing more roots per unit of Zn available, or retranslocating more Zn from other tissues to the roots, or all of the above. To investigate this, Zn content of Nipponbare, Zn-efficient and inefficient genotypes was measured in the seed (before sowing) and in the shoot and the roots at different time points. Seeds from Zn-inefficient genotypes contained 22% less Zn than seeds from Zn-efficient genotypes (Table 1, Supplementary Table S3). Nipponbare seeds also contained less Zn, compared to those of Zn-efficient genotypes, but only by 9% (Table 1). However, at 0 WAT, seedlings of all genotypes contained the same total amount of Zn in their shoot and roots, though its distribution was slightly different (Figures 3A,B and Supplementary Table S4). Zn-inefficient genotypes had a higher proportion of Zn in the roots, resulting in a higher root to shoot ratio (0.24) at 0 WAT, compared to the Zn-efficient genotypes (0.17) and Nipponbare (0.17; Figure 3B). At 2 WAT to Zn-free nutrient solution, no difference in total Zn content was observed for either Nipponbare, Zn-inefficient or efficient genotypes, confirming that no Zn uptake took place (Figure 3A). However, during the 2-week-growth period, 17% of shoot-Zn was retranslocated to roots in Zn-efficient plants, compared to only 11% in Zn-inefficient plants (Figure 3C). Impressively, Nipponbare retranslocated 25% of its shoot-Zn to roots. This resulted in an increase in root-Zn of 113% for Nipponbare and 109% for Zn-efficient genotypes, while the root-Zn of Zn-inefficient genotypes only increased by 41% (Figure 3D). As a result, the Zn root to shoot ratio of Nipponbare and Zn-efficient genotypes increased by 185 and 118%, respectively, while that of Zn-inefficient genotypes only increased by 60% (Figure 3B).

Bottom Line: Zinc (Zn) deficiency is one of the leading nutrient disorders in rice (Oryza sativa).We therefore conclude that the rate of crown root initiation was differentially affected by Zn deficiency between genotypes.Rapid crown root development, following transplanting, was identified as a main causative trait for tolerance to Zn deficiency and better Zn retranslocation from shoot to root was a key attribute of Zn-efficient genotypes.

View Article: PubMed Central - PubMed

Affiliation: Crop, Livestock and Environment Division, Japan International Research Center for Agricultural Sciences Tsukuba, Japan.

ABSTRACT
Zinc (Zn) deficiency is one of the leading nutrient disorders in rice (Oryza sativa). Many studies have identified Zn-efficient rice genotypes, but causal mechanisms for Zn deficiency tolerance remain poorly understood. Here, we report a detailed study of the impact of Zn deficiency on crown root development of rice genotypes, differing in their tolerance to this stress. Zn deficiency delayed crown root development and plant biomass accumulation in both Zn-efficient and inefficient genotypes, with the effects being much stronger in the latter. Zn-efficient genotypes had developed new crown roots as early as 3 days after transplanting (DAT) to a Zn deficient field and that was followed by a significant increase in total biomass by 7 DAT. Zn-inefficient genotypes developed few new crown roots and did not increase biomass during the first 7 days following transplanting. This correlated with Zn-efficient genotypes retranslocating a higher proportion of shoot-Zn to their roots, compared to Zn-inefficient genotypes. These latter genotypes were furthermore not efficient in utilizing the limited Zn for root development. Histological analyses indicated no anomalies in crown tissue of Zn-efficient or inefficient genotypes that would have suggested crown root emergence was impeded. We therefore conclude that the rate of crown root initiation was differentially affected by Zn deficiency between genotypes. Rapid crown root development, following transplanting, was identified as a main causative trait for tolerance to Zn deficiency and better Zn retranslocation from shoot to root was a key attribute of Zn-efficient genotypes.

No MeSH data available.


Related in: MedlinePlus