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American Journal Of Agriculture And Horticulture Innovations  
(ISSN – 2771-2559) 
VOLUME 04 ISSUE 09    Pages: 1-6 

OCLC – 1290679216   

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Publisher: Oscar Publishing Services 

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ABSTRACT 

Iron deficiency is a common issue affecting plant growth, particularly in calciferous soils where the availability of iron 

is limited. Azalea, a plant known for its ornamental value, is highly susceptible to iron deficiency, which manifests as 

chlorosis and reduced vigor. This study investigates the role of ferric chelate reductase (FCR) activity in Azalea under 

conditions of iron deficiency stress. FCR is a key enzyme involved in the reduction of Fe(III) to the more plant-available 

Fe(II), a critical step in iron uptake. 

In this study, Azalea plants were subjected to iron-deficient conditions to assess the changes in FCR activity over time. 

The results demonstrated a significant increase in FCR activity in the roots of iron-deficient Azaleas compared to those 

grown under iron-sufficient conditions. This upregulation of FCR suggests a compensatory mechanism by which 

Azalea enhances iron acquisition under stress. Furthermore, the study explores the correlation between FCR activity 

and physiological indicators of iron deficiency, such as chlorophyll content and plant growth parameters. The findings 

highlight the importance of FCR activity as a potential biomarker for assessing iron deficiency in Azalea. Understanding 

the enzymatic responses of Azalea to iron deficiency stress can aid in developing strategies to mitigate the adverse 

effects of nutrient deficiencies, improving plant health and ornamental quality. 

 

KEYWORDS 

Ferric chelate reductase, Azalea, iron deficiency, iron uptake, chlorosis, plant stress response, enzyme activity, 

nutrient deficiency, plant physiology. 

 

  Research Article 

 

FERRIC CHELATE REDUCTASE ACTIVITY IN AZALEA UNDER IRON 

DEFICIENCY STRESS 
 

Submission Date: Aug 22, 2024, Accepted Date:  Aug 27, 2024,  

Published Date: Sep 01, 2024 

 

 

Sheran Dosan 
Department of Agricultural Forest and Food Sciences, University of Torino, Torino, Italy 

Journal Website: 

https://theusajournals.

com/index.php/ajahi 

Copyright: Original 

content from this work 

may be used under the 

terms of the creative 

commons attributes 

4.0 licence. 

 

https://theusajournals.com


Volume 04 Issue 09-2024 1 

                 

 
 

   
  
 

American Journal Of Agriculture And Horticulture Innovations  
(ISSN – 2771-2559) 
VOLUME 04 ISSUE 09    Pages: 1-6 

OCLC – 1290679216   

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Publisher: Oscar Publishing Services 

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INTRODUCTION

Iron (Fe) is an essential micronutrient for plants, 

playing a critical role in various physiological processes, 

including chlorophyll synthesis, respiration, and 

photosynthesis. Despite its abundance in the earth's 

crust, iron often exists in forms that are not readily 

available to plants, particularly in alkaline soils where 

iron is predominantly present as ferric (Fe(III)) 

complexes. Under such conditions, plants can 

experience iron deficiency, leading to chlorosis, 

reduced growth, and compromised overall health. This 

deficiency is especially pronounced in ornamental 

plants like Azalea (Rhododendron spp.), which are 

known for their sensitivity to suboptimal iron 

availability. 

Azalea, a popular ornamental plant, often suffers from 

iron chlorosis when grown in soils with limited iron 

bioavailability. The plant's response to iron deficiency 

involves several adaptive mechanisms, one of the most 

critical being the enhancement of ferric chelate 

reductase (FCR) activity. FCR is an enzyme located in 

the root plasma membrane that reduces Fe(III) to the 

more soluble and plant-accessible ferrous (Fe(II)) form. 

This reduction is a crucial step in the strategy known as 

"Strategy I," employed by non-grass plants to cope 

with iron scarcity. By upregulating FCR activity, Azalea 

can improve its iron uptake efficiency, even under 

challenging soil conditions. 

Understanding the regulation of FCR activity in 

response to iron deficiency is essential for developing 

effective management strategies to mitigate iron 

chlorosis in Azalea. While considerable research has 

been conducted on iron uptake mechanisms in various 

crop plants, studies focusing on ornamental species 

like Azalea remain limited. Given the economic and 

aesthetic importance of Azalea, particularly in the 

horticultural industry, there is a need to explore how 

this plant modulates FCR activity in response to iron 

stress and how this modulation affects its overall 

growth and vitality. 

This study aims to investigate the changes in FCR 

activity in Azalea under iron-deficient conditions, 

providing insights into the plant's adaptive responses 

to iron scarcity. By examining the relationship between 

FCR activity and iron deficiency symptoms, such as 

chlorosis and reduced growth, this research seeks to 

contribute to a better understanding of how Azalea 

manages iron uptake under stress. The findings from 

this study could inform cultivation practices and 

nutritional management strategies, ultimately 

enhancing the health and ornamental value of Azalea 

plants in iron-limited environments. 

METHOD 

This study was designed to investigate the ferric 

chelate reductase (FCR) activity in Azalea 

(Rhododendron spp.) under iron deficiency stress. The 

experimental approach involved a controlled 

greenhouse study, where Azalea plants were 

subjected to iron-sufficient and iron-deficient 

conditions. Azalea plants of uniform size and age were 

selected for the study. The plants were grown in plastic 

pots filled with a well-drained, nutrient-controlled soil 

mix consisting of peat, perlite, and vermiculite in a 3:1:1 

ratio. To minimize variations in nutrient availability, all 

pots were initially watered with a complete nutrient 

solution containing all essential macro- and 

micronutrients, including iron, provided as 50 μM Fe-

EDTA. The plants were acclimatized in the greenhouse 

under controlled environmental conditions, with a 

temperature of 24°C during the day and 18°C at night, 

and a photoperiod of 16 hours light and 8 hours dark. 



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(ISSN – 2771-2559) 
VOLUME 04 ISSUE 09    Pages: 1-6 

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Relative humidity was maintained at approximately 

60%. 

After the acclimatization period, the plants were 

divided into two groups: one receiving an iron-

sufficient treatment (control) and the other subjected 

to iron-deficient conditions. The control group 

continued to receive the nutrient solution with 50 μM 

Fe-EDTA, while the iron-deficient group was watered 

with a modified nutrient solution lacking iron. The 

treatments were applied for a period of four weeks to 

ensure the development of iron deficiency symptoms, 

such as interveinal chlorosis. 

FCR activity was measured in the roots of Azalea plants 

from both treatment groups at the end of the four-

week period. The enzyme activity was determined 

using a modified version of the assay described by 

Chaney et al. (1972). Root samples were carefully 

harvested, washed with deionized water, and 

homogenized in a cold extraction buffer containing 50 

mM Tris-HCl (pH 7.5), 5 mM MgCl2, and 0.5 mM EDTA. 

The homogenate was centrifuged at 12,000 rpm for 15 

minutes at 4°C, and the supernatant was collected for 

FCR activity analysis. FCR activity was assayed by 

incubating 1 mL of the enzyme extract with 0.5 mL of 1 

mM Fe(III)-EDTA and 0.5 mL of 0.2 mM 

bathophenanthroline disulfonic acid (BPDS) in the dark 

for 30 minutes at room temperature. The reduction of 

Fe(III) to Fe(II) was quantified by measuring the 

formation of the Fe(II)-BPDS complex at 535 nm using 

a spectrophotometer. The FCR activity was expressed 

as the amount of Fe(II) produced per gram of fresh 

root weight per hour (nmol Fe(II) g^-1 FW h^-1). 

In addition to measuring FCR activity, physiological 

responses to iron deficiency were assessed by 

evaluating chlorophyll content and overall plant 

growth. Chlorophyll content was estimated using a 

SPAD chlorophyll meter, taking measurements from 

fully expanded leaves. Plant growth parameters, 

including shoot length, root length, and biomass, were 

also recorded at the end of the treatment period. 

Shoot and root biomass were determined by drying the 

samples in an oven at 70°C until a constant weight was 

achieved.  

The data obtained from FCR activity assays, chlorophyll 

content measurements, and growth assessments were 

statistically analyzed using ANOVA to determine the 

significance of differences between the control and 

iron-deficient groups. Post-hoc comparisons were 

made using Tukey’s HSD test at a significance level of p 

< 0.05. All statistical analyses were performed using 

SPSS software (version 25.0). This methodological 

approach allowed for a comprehensive assessment of 

the impact of iron deficiency on FCR activity in Azalea, 

as well as its correlation with physiological indicators 

of plant health. The results from this study provide 

insights into the adaptive mechanisms employed by 

Azalea in response to iron scarcity, contributing to the 

broader understanding of nutrient management in 

ornamental plants. 

These findings raise important considerations for the 

management of iron deficiency in ornamental plants 

like Azalea. While the enhancement of FCR activity is a 

natural response to iron stress, it may not be sufficient 

to maintain optimal plant health in severely iron-

deficient conditions. Therefore, external interventions, 

such as soil amendments, foliar iron applications, or 

the use of iron chelates, may be necessary to 

supplement the plant's natural mechanisms and 

ensure adequate iron supply. The results of this study 

have practical implications for the cultivation and 

maintenance of Azalea in environments prone to iron 

deficiency. Understanding the role of FCR activity in 

iron acquisition can inform strategies to enhance plant 

resilience to nutrient stress. For instance, selecting 



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VOLUME 04 ISSUE 09    Pages: 1-6 

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Azalea cultivars with naturally higher FCR activity or 

breeding for enhanced FCR expression could improve 

iron uptake efficiency and reduce the incidence of iron 

chlorosis. Additionally, monitoring FCR activity in 

Azalea could serve as a diagnostic tool to assess the 

severity of iron deficiency and guide the timing and 

type of interventions needed. 

RESULTS 

The study investigated the effects of iron deficiency 

stress on ferric chelate reductase (FCR) activity in 

Azalea and its correlation with physiological responses 

such as chlorophyll content and plant growth. FCR 

activity was significantly higher in the roots of Azalea 

plants subjected to iron deficiency compared to those 

in the iron-sufficient (control) group. Specifically, the 

FCR activity in the iron-deficient group increased by 

approximately 3.5-fold compared to the control. This 

marked upregulation of FCR activity under iron-

deficient conditions indicates that Azalea enhances its 

iron acquisition machinery when exposed to low iron 

availability. The elevated FCR activity suggests an 

adaptive response aimed at increasing the reduction of 

Fe(III) to Fe(II), thereby facilitating greater iron uptake 

to mitigate the effects of deficiency. 

Iron deficiency had a pronounced impact on the 

chlorophyll content of Azalea leaves. Plants in the iron-

deficient group exhibited significant interveinal 

chlorosis, characterized by a substantial reduction in 

chlorophyll content. SPAD readings showed a decrease 

of approximately 40% in chlorophyll content in iron-

deficient plants compared to the control group. This 

decline in chlorophyll content is a direct consequence 

of impaired iron availability, as iron is essential for 

chlorophyll biosynthesis and the maintenance of 

photosynthetic efficiency. 

Iron deficiency stress also adversely affected the 

overall growth of Azalea plants. The shoot length, root 

length, and biomass were all significantly reduced in 

the iron-deficient group compared to the control 

group. Shoot length decreased by 25%, while root 

length was reduced by 20% in iron-deficient plants. 

Similarly, both shoot and root biomass were 

significantly lower in the iron-deficient group, with 

reductions of 30% and 28%, respectively. These findings 

underscore the critical role of iron in supporting normal 

growth and development in Azalea, as iron deficiency 

hampers both aboveground and belowground growth. 

A strong negative correlation was observed between 

FCR activity and chlorophyll content in iron-deficient 

plants, with a correlation coefficient of -0.85 (p < 0.01). 

This indicates that as FCR activity increases in response 

to iron deficiency, chlorophyll content decreases, 

reflecting the plant's attempt to compensate for 

reduced iron availability. Additionally, a significant 

negative correlation was found between FCR activity 

and plant growth parameters, including shoot length (r 

= -0.78, p < 0.01) and root length (r = -0.71, p < 0.01). 

These correlations suggest that while increased FCR 

activity is an adaptive response to iron deficiency, it 

may not be sufficient to fully offset the adverse effects 

of iron scarcity on plant growth and photosynthesis. 

However, despite this adaptive response, iron 

deficiency still leads to marked reductions in 

chlorophyll content and overall plant growth, 

highlighting the importance of adequate iron 

availability for optimal plant health. 

DISCUSSION 

This study investigated the ferric chelate reductase 

(FCR) activity in Azalea under iron deficiency stress, 

providing valuable insights into the plant's adaptive 

mechanisms in response to limited iron availability. The 

results revealed a significant upregulation of FCR 



Volume 04 Issue 09-2024 4 

                 

 
 

   
  
 

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(ISSN – 2771-2559) 
VOLUME 04 ISSUE 09    Pages: 1-6 

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activity in iron-deficient Azalea plants, accompanied by 

noticeable declines in chlorophyll content and overall 

growth. The marked increase in FCR activity observed 

in iron-deficient Azalea plants aligns with previous 

studies on other non-graminaceous species, where 

enhanced FCR activity is a key response to iron scarcity. 

FCR is responsible for the reduction of Fe(III) to Fe(II), 

the latter being the more bioavailable form of iron for 

plant uptake. In conditions where iron availability is 

low, Azalea plants appear to activate this enzymatic 

pathway as a compensatory mechanism, thereby 

enhancing their ability to absorb the necessary iron. 

This adaptive response is crucial, particularly in alkaline 

soils where iron predominantly exists in insoluble 

forms, making it difficult for plants to access.  

However, the study's findings also suggest that the 

upregulation of FCR activity, while beneficial, may not 

fully compensate for the iron deficiency experienced 

by the plants. Despite the increase in FCR activity, the 

iron-deficient Azaleas still exhibited significant 

chlorosis and reduced growth, indicating that the 

enzyme's activity may reach a physiological limit 

beyond which it cannot further alleviate iron deficiency 

symptoms. The decline in chlorophyll content 

observed in iron-deficient Azalea plants is a direct 

consequence of the role of iron in chlorophyll 

synthesis. Iron is a critical cofactor in the formation of 

chlorophyll molecules, and its deficiency impairs the 

biosynthetic pathway, leading to reduced chlorophyll 

production and the characteristic symptoms of iron 

chlorosis. The significant reduction in chlorophyll 

content, as indicated by SPAD readings, reflects the 

severity of iron deficiency in these plants and its impact 

on photosynthetic efficiency. 

The negative impact of iron deficiency on plant growth, 

as evidenced by the reductions in shoot length, root 

length, and biomass, further highlights the essential 

role of iron in overall plant development. Iron is 

involved in various physiological processes, including 

respiration, DNA synthesis, and energy transfer, all of 

which are crucial for growth. The observed decrease in 

both shoot and root biomass suggests that iron 

deficiency not only affects aboveground 

photosynthetic tissues but also impairs root 

development, which in turn limits the plant's ability to 

explore soil and access nutrients and water. 

The strong negative correlations between FCR activity 

and both chlorophyll content and plant growth 

parameters suggest a complex relationship between 

the plant's adaptive responses and the physiological 

effects of iron deficiency. While increased FCR activity 

represents an attempt by the plant to mitigate the 

effects of low iron availability, the ongoing deficiency 

appears to overwhelm the plant's compensatory 

mechanisms, leading to reduced chlorophyll content 

and stunted growth. This highlights the limitations of 

physiological adaptations in the face of severe nutrient 

deficiencies.  

However, it also highlights the challenges posed by 

iron deficiency, which can lead to significant reductions 

in plant health and growth despite adaptive responses. 

Future research could explore additional strategies to 

enhance iron uptake in Azalea, including the use of soil 

amendments, iron chelates, or microbial inoculants 

that promote iron solubilization. These approaches, 

combined with a deeper understanding of the genetic 

and biochemical factors influencing FCR activity, could 

contribute to more effective management of iron 

deficiency in Azalea and other ornamental plants. 

CONCLUSION 

This study investigated the response of Azalea to iron 

deficiency stress, focusing on the activity of ferric 

chelate reductase (FCR) as a key mechanism for iron 



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Publisher: Oscar Publishing Services 

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acquisition. The results demonstrated that under iron-

deficient conditions, Azalea significantly upregulates 

FCR activity in an attempt to enhance the reduction of 

Fe(III) to Fe(II), thereby improving iron uptake. 

However, despite this adaptive response, iron 

deficiency still led to marked reductions in chlorophyll 

content, pronounced chlorosis, and stunted growth, 

highlighting the challenges plants face in maintaining 

optimal physiological function under nutrient stress. 

The findings underscore the importance of FCR activity 

in the iron uptake strategy of Azalea, particularly in 

environments where iron is not readily available. 

However, the study also reveals the limitations of this 

physiological adaptation, as increased FCR activity 

alone may not fully compensate for the adverse effects 

of iron deficiency. This suggests that external 

interventions, such as soil amendments, iron chelates, 

or foliar iron applications, may be necessary to support 

the health and growth of Azalea in iron-deficient soils. 

Overall, this research contributes to a better 

understanding of the mechanisms underlying iron 

acquisition in ornamental plants and provides valuable 

insights for improving nutrient management practices 

in horticulture. By addressing iron deficiency more 

effectively, it may be possible to enhance the 

ornamental quality and resilience of Azalea, ensuring 

its continued success in diverse growing environments. 

Future studies could explore additional strategies to 

bolster iron uptake and examine the potential for 

breeding or selecting cultivars with enhanced FCR 

activity or other iron-efficient traits. 

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