Abstract
To explore the zinc stress response in eddo, plants were grown for 15 d in hydroponic solutions containing 1 (control), 200, and 1000 μM zinc, and the hydathode function and changes in the contents of various elements in these plants were investigated. Under 1000 μM zinc, the dry weights of leaf blades and roots are decreased by 17 and 42%, respectively. The zinc contents in leaf blades, petioles, corms, and roots increased with increasing zinc levels in the solution. The zinc content in roots was 6.57 mg g−1 dry weight, which was 2.8–4.3 times higher than in other plant parts under 1000 μM zinc. These results demonstrate that the severe root damage occurring under 1000 μM zinc is due to higher zinc content in the roots. Under zinc stress, the contents of iron and copper in roots increased, but the contents of magnesium and calcium in petioles, corms, and roots, iron in leaf blades and corms, and manganese in petioles and corms decreased. In the guttation fluid, the concentrations of zinc, magnesium, and potassium increased, while the iron concentration decreased under 1000 μM zinc. Thus, elemental changes occurred in the guttation fluid as well as in different plant parts in eddo. In the 200 and 1000 μM zinc treatments, the amount of zinc eliminated via guttation was 2.8 and 8.5 times higher, respectively, than in the control. The results indicate that guttation partly contributes to the excretion of excess zinc under zinc stress conditions.
Highlights
Eddo [Colocasia esculenta (L.) Schott var. antiquorum Hubbard & Rehder] belongs to the taro group in the family Araceae and is cultivated mainly in Asia as a staple food
Guttation can facilitate the excretion of boron (B) in banana (Shapira et al, 2013), calcium (Ca) in eddo (Islam & Kawasaki, 2015), and arsenic in Pteris vittata fronds (Cantamessa et al, 2015) when those elements are present at excessive concentrations
Mizuno et al (2002) suggested that unbalanced elements could be excreted via guttation to adjust ion concentrations in Petasites japonicus var. giganteus and Polygonum cuspidatum growing on ultramafic soil
Summary
Eddo [Colocasia esculenta (L.) Schott var. antiquorum Hubbard & Rehder] belongs to the taro group in the family Araceae and is cultivated mainly in Asia as a staple food. Excess Zn was found to accumulate in the edible parts of taro cultivated in lead/Zn mine waste-affected areas (Liu et al, 2005) In plants such as sugar beet, rice, and sorghum, Zn toxicity can reduce growth by disrupting physiological processes such as photosynthesis, respiration, transpiration, and nutrient distribution (Ali et al, 2000; Lin et al, 2005; Mirshekali et al, 2012; Sagardoy et al, 2010; Subba et al, 2014). We aimed to elucidate the mechanism of the Zn stress response in eddo by investigating changes in the contents of various elements in different plant parts as well as in guttation fluid. We explored whether guttation contributes to ion homeostasis in eddo under Zn stress conditions
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