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Excess copper effects on growth, uptake of water and nutrients, carbohydrates, and PSII photochemistry revealed by OJIP transients in Citrus seedlings
Seedlings of ‘Shatian pummelo’ ( Citrus grandis ) and ‘Xuegan’ ( Citrus sinensis ) were supplied daily with nutrient solution at a concentration of 0.5 (control), 100, 200, 300, 400, or 500 μM CuCl 2 for 6 months. Thereafter, seedling growth; leaf, root, and stem levels of nutrients; leaf gas exchan...
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| Published in: | Environmental science and pollution research international 2019-10, Vol.26 (29), p.30188-30205 |
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| Main Authors: | , , , , , , |
| Format: | Article |
| Language: | English |
| Subjects: | |
| Citations: | Items that this one cites Items that cite this one |
| Online Access: | Get full text |
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| Summary: | Seedlings of ‘Shatian pummelo’ (
Citrus grandis
) and ‘Xuegan’ (
Citrus sinensis
) were supplied daily with nutrient solution at a concentration of 0.5 (control), 100, 200, 300, 400, or 500 μM CuCl
2
for 6 months. Thereafter, seedling growth; leaf, root, and stem levels of nutrients; leaf gas exchange; levels of pigments; chlorophyll
a
fluorescence (OJIP) transients and related parameters; leaf and root relative water content; levels of nonstructural carbohydrates; H
2
O
2
production rate; and electrolyte leakage were comprehensively examined (
a
) to test the hypothesis that Cu directly damages root growth and function, thus impairing water and nutrient uptake and hence inhibiting shoot growth; (
b
) to establish whether the Cu-induced preferential accumulation of Cu in the roots is involved in Cu tolerance of
Citrus
; and (
c
) to elucidate the possible causes for the Cu-induced decrease in photosynthesis. Most of the growth and physiological parameters were greatly altered only at 300–500 μM (excess) Cu-treated seedlings. Cu supply increased the level of Cu in the roots, stems, and leaves, with a greater increase in the roots than that in the stems and leaves. Many of the fibrous roots became rotten and died under excess Cu. These findings support the hypothesis that Cu directly damages root growth and function, thus impairing water and nutrient uptake and hence inhibiting shoot growth, and the conclusion that the preferential accumulation of Cu in the roots under excess Cu is involved in the tolerance of
Citrus
to Cu toxicity. The lower CO
2
assimilation in excess Cu-treated leaves was caused mainly by nonstomatal factors, including structural damage to thylakoids, feedback inhibition due to increased accumulation of nonstructural carbohydrates, decreased uptake of water and nutrients, increased production of reactive oxygen species, and impaired photosynthetic electron transport chain. Also, we discussed the possible causes for the excess Cu-induced decrease in leaf pigments and accumulation of nonstructural carbohydrates in the roots and leaves. |
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| ISSN: | 0944-1344 1614-7499 |
| DOI: | 10.1007/s11356-019-06170-2 |