Cadmium Movement in Young Cacao Plants

Jim Crocker
21st June, 2024

Cadmium Movement in Young Cacao Plants

This model illustrates that cadmium absorbed by Theobroma cacao seedlings is transported from the roots to the stem via the xylem and subsequently reallocated through the phloem to supply developing leaves and roots.

Image adapted from: Blommaert et al. / CC BY (Source)

Key Findings

  • The study was conducted in northern Honduras to analyze Cd accumulation in 11 cacao cultivars
  • Cd levels in rootstocks, scions, and leaves were more closely linked to soil Cd than in beans
  • Different cacao cultivars showed significant variations in Cd levels in mature beans
Cadmium (Cd) is a heavy metal that poses significant risks to plants, animals, and humans even at low concentrations. Recent regulations by the European Union in 2019 have heightened the urgency to address Cd contamination in cacao beans, especially from Latin America, where levels often exceed acceptable limits. A recent study conducted by researchers at Université Grenoble Alpes aims to address this problem by exploring differences in Cd uptake and translocation among various cacao cultivars[1]. The study involved a long-term trial at CEDEC-JAS in northern Honduras, where 11 cacao cultivars were analyzed for their Cd accumulation patterns. Researchers sampled different plant parts, including rootstocks, scions, leaves, and beans, from three replicate trees per cultivar. They also examined the soil around each tree to understand the relationship between soil Cd levels and plant Cd concentrations. Results showed that Cd concentrations in rootstocks, scions, and leaves were more closely correlated with available soil Cd than bean Cd concentrations. Specifically, the correlation coefficients were R2 = 0.56 for rootstocks, R2 = 0.59 for scions, and R2 = 0.46 for leaves, compared to R2 = 0.26 for beans. This indicates that while vegetative parts of the plant absorb Cd in relation to soil levels, the beans accumulate Cd differently. Notably, significant variations in bean Cd concentrations were observed among different cultivars, particularly during the bean maturation stage. These findings suggest that the differences in Cd concentrations in mature beans are likely due to cultivar-specific mechanisms affecting Cd transfer from vegetative parts to the beans. One possible explanation is the variation in xylem-to-phloem transfer of Cd among cultivars. This is supported by earlier studies on rice, which identified nodes as critical sites for xylem-to-phloem transfer, playing a pivotal role in Cd transport from soil to grains[2]. The study's approach to understanding Cd accumulation in cacao beans also aligns with the broader research on metal hyperaccumulation and hypertolerance in plants. These plants have evolved specialized traits to thrive in metal-rich environments, providing valuable insights into the physiological, molecular, and genetic mechanisms underlying metal uptake and tolerance[3]. By identifying cultivars with low Cd transfer to beans, the study offers a practical solution to reduce Cd levels in cacao, making it safer for consumption. The research methods included sampling various plant parts and soil, followed by analyzing Cd concentrations using techniques that measure labile metal pools. This approach is similar to the isotope dilution technique used to measure labile pools of metals like Cu in soils[4]. Such methods are crucial for accurately assessing metal availability and uptake in plants. In conclusion, the study by Université Grenoble Alpes provides a promising avenue for reducing Cd levels in cacao beans by selecting cultivars with lower Cd transfer from vegetative parts to beans. This approach not only addresses the immediate concern of meeting regulatory standards but also contributes to our understanding of metal uptake and translocation in plants. By building on previous research, this study offers a comprehensive solution to a pressing agricultural and public health issue.

AgricultureBiochemPlant Science

References

Main Study

1) Evidence of cadmium transport via the phloem in cacao seedlings

Published 20th June, 2024

https://doi.org/10.1007/s11104-024-06753-0

Related Studies

2) Tracing cadmium from culture to spikelet: noninvasive imaging and quantitative characterization of absorption, transport, and accumulation of cadmium in an intact rice plant.

https://doi.org/10.1104/pp.109.151035

3) Metal hyperaccumulation in plants.

https://doi.org/10.1146/annurev-arplant-042809-112156

4) Measurement of labile Cu in soil using stable isotope dilution and isotope ratio analysis by ICP-MS.

Journal: Analytical and bioanalytical chemistry, Issue: Vol 380, Issue 5-6, Nov 2004


Related Articles

An unhandled error has occurred. Reload 🗙