Effects Of Aluminium Toxicity On Root Morphology And Physiology Of Two Maize Hybrids
Acid soils in Malaysia account for 72% of the country that was classified under Ultisols and Oxisols. Crop production is not favorable in highly weathered Ultisols and Oxisols, due to aluminium (Al) and manganese (Mn) toxicities as well as calcium (Ca) and magnesium (Mg) deficiencies. Acid soils...
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| Format: | Thesis |
| Language: | English English |
| Published: |
2007
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| Online Access: | http://psasir.upm.edu.my/id/eprint/5498/1/FP_2007_20.pdf http://psasir.upm.edu.my/id/eprint/5498/ |
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| Summary: | Acid soils in Malaysia account for 72% of the country that was classified under
Ultisols and Oxisols. Crop production is not favorable in highly weathered Ultisols and
Oxisols, due to aluminium (Al) and manganese (Mn) toxicities as well as calcium (Ca)
and magnesium (Mg) deficiencies. Acid soils with high Al saturation (> 60%) induce
water stress and retards plant growth. Al toxicity and water stress affects every aspect
of plant growth, including the anatomy, morphology, physiology and biochemistry.
Therefore, a detail understanding of the physiological characteristics of Al stress, will
lead to improvement of maize (Zea mays L.) with tolerance to Al that can be grown on
Ultisols and Oxisols.
Three experiments were conducted to study the effects of aluminium toxicity on root
morphology and physiology of two maize hybrids (Putra J-58 and C-7). Experiments
were conducted in the laboratory and at Field two, Faculty of Agriculture, Universiti
Putra Malaysia. The experiments were conducted to study the effect of Al on seed
germination, short-term effect of Al on root structure and effect of high Al concentrations on maize growth. The experimental designs were randomized
complete block design in factorial arrangement, and replicated three times.
Overall results showed that maize seeds were impermeable to Al, even though seeds
were soaked in 300 μM Al for 8 h, the seeds when sliced and stained with 0.2%
hematoxylin showed that the embryo was not stained. Moreover, seed germination
was normal when soaked in Al solution, but after germination, root growth was
restricted and root tip became brown, stubby, with lesions on the root surface. The
total root length of C-7 was significantly longer than Putra J-58.
Hematoxylin staining showed that tolerance level of Putra J-58 was considered as
intermediate tolerance to Al, while C-7 was sensitive to Al. Al uptake appears to take
place within 30 min, and based on the root morphological observations, Al disrupted
root cells within 24 h as indicated by lesions in the cortex tissue of the root tip.
High Al concentrations (278 and 556 μM Al) inhibited root growth as well as root
branching and induced water stress symptoms. After two days in the Al solution,
leaves showed interveinal chlorosis, a symptom of Mg deficiency and supported by
result of leaf analysis. This symptom was observed on plant grown in solutions with
278 and 556 μM Al. Ca content in the shoot of maize grown in 0 and 556 μM Al were
8.81 and 4.41 μg/g of DM, respectively. Moreover, Mg content in the shoot of maize
grown in 0 and 556 μM Al were 5.51 and 2.33 μg/g of DM, respectively. After six
days in the nutrient solution containing 556 μM Al, root and shoot dry matter
reduced by 61.1% and 34.8%, respectively, compared to control. In addition, stomatal resistance increased by 84.6% and transpiration rate was reduced 41.8% by
556 μM Al, respectively, compared to control.
Al toxicity induced root lesions, stubby roots and deep-cracking on the epidermal
tissue of the roots. However, the degree of root inhibition or root damage and the
decreasing plant physiological activities were dependent on the level of Al present.
Maize root growth appears to show a linear or almost exponential response to Al
toxicity. |
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