Effects of exogenous silicon application on physiological parameters， root architecture and diameter distribution of maize under cadmium stress

doi:10.11686/cyxb2021499

Abstract

Abstract:

The aim of this study was to explore the effect of silicon （Si） on the root architecture， root diameter distribution and seedling growth of maize （Zea mays） under cadmium （Cd） stress， and to find an effective way to alleviate the toxicity of Cd on maize seedlings. The experiment had eight treatments： Control （no Cd， no Si）， Cd only and six different concentrations of applied Si （0.25， 0.50， 1.00， 1.50， 2.00 and 4.00 mmol·L^-1 Si） with hydroponic cultivation to test the Cd concentration and content of maize， growth-related indicators， photosynthetic indicators， and root architecture and diameter. The root architecture was assessed by classifying roots into four diameter classes （Ⅰ， <0.5 mm； Ⅱ， 0.5-1.0 mm； Ⅲ， 1.0-1.5 mm； Ⅳ， <1.5 mm） and the plant characteristics of the various treatments were compared. It was found that Cd stress inhibited the growth and development of maize seedlings， the chlorophyll content increased， and the photosynthetic parameters were significantly decreased. Total root length， root surface area， root volume， number of root tips and root forks， including root length of diameter classes Ⅰ-Ⅲ， root surface area and root volume of the diameter classes of Ⅰ-Ⅱ were decreased significantly. After applying different concentrations of Si， the Cd accumulation of plants was reduced by 12.65%-88.07%， and the Cd toxicity was alleviated to varying extents. Alleviation of Cd toxicity manifested as increase in plant height， main root length， biomass and tolerance index. In plants with the 0.25 mmol·L^-1 concentration of Si applied， the total chlorophyll content was increased by 11.76%. Under Cd stress， stomatal conductance， intercellular CO₂ concentration and transpiration rate were significantly increased with the applied Si concentration of 1.00 mmol·L^-1. The total root length， number of root forks， and the root length， root surface area and root volume in the Class Ⅰ diameter range were maximized at the Si concentration of 1.00 mmol·L^-1； The root surface area and root volume peaked at the Si concentration of 1.50 mmol·L^-1. Correlation analysis showed that the total root length and root surface area of roots in diameter classes Ⅰ-Ⅲ， and the root volume of roots in diameter classes Ⅰ-Ⅱ diameter range were significantly negatively correlated with Cd translocation index. Comprehensive evaluation of the effects of different treatment showed that the 1.00 mmol·L^-1 exogenous Si treatment provided the most efficacious alleviation of 50 μmol·L^-1 Cd toxicity in maize. The results showed that Si application reduced the absorption， accumulation and transport of Cd by the roots of maize seedlings， and reduced the concentration and accumulation of Cd in the shoots. These effects reduced the impact of Cd on the photosynthetic system， increased the biomass of maize seedlings， and promoted the distribution of photosynthetic products to the root system， reducing the impact of Cd on root architecture， improving the ability of maize to tolerate Cd， and alleviating its toxic effects.

Key words: maize, cadmium, silicon, root architecture, root classification

Ying JIANG, Chang WEI, Qiu-juan JIAO, Feng-min SHEN, Ge-zi LI, Xue-hai ZHANG, Fang YANG, Hai-tao LIU. Effects of exogenous silicon application on physiological parameters， root architecture and diameter distribution of maize under cadmium stress[J]. Acta Prataculturae Sinica, 2022, 31(9): 139-154.

Figures/Tables 12

References 51

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项目 Item	CK	Cd₅₀
项目 Item	CK	Si₀	Si_0.25	Si_0.5	Si₁	Si_1.5	Si₂	Si₄
总根长RL （cm）	966.95±120.15a	367.71±32.39b	380.44±64.23b	393.17±142.11b	484.58±115.19b	433.66±43.93b	436.79±41.96b	206.38±19.77c
各分级总根长RL of each class （cm）
Ⅰ	794.09±104.54a	266.37±14.84b	290.32±43.70b	290.55±129.39b	358.25±98.33b	297.63±39.49b	284.08±28.68b	115.60±17.26c
Ⅱ	146.80±17.46a	86.01±20.61bcd	67.94±20.62d	79.36±14.49bcd	101.85±14.47b	97.94±5.46bc	130.00±15.51a	71.24±5.93cd
Ⅲ	16.10±2.26b	9.43±1.67c	11.83±2.01bc	13.17±1.46bc	15.30±2.37bc	22.39±7.32a	13.67±4.06bc	10.61±1.19bc
Ⅳ	9.60±3.06b	5.85±1.59b	10.31±0.66b	10.02±2.99b	9.13±2.70b	15.49±5.20a	8.93±3.13b	8.83±0.89b
根表面积SA （cm²）	100.56±10.31a	47.73±3.24de	52.42±8.81cde	56.09±14.61bcd	68.12±13.74bc	72.87±9.37b	68.21±4.97bc	36.29±4.09e
各分级根表面积SA of each class （cm²）
Ⅰ	42.73±5.91a	15.93±0.73b	19.04±2.73b	19.20±8.51b	25.10±7.50b	22.21±2.28b	20.62±2.25b	6.66±1.09c
Ⅱ	32.49±3.91a	18.75±4.14cd	15.48±5.06d	17.75±3.50cd	23.11±3.12bc	22.60±1.28bc	28.80±3.31ab	15.20±2.07d
Ⅲ	6.05±0.87b	3.57±0.59b	4.45±0.78b	4.93±0.53b	5.69±0.82b	8.62±2.93a	5.15±1.56b	4.08±0.48b
Ⅳ	7.43±2.33b	4.68±1.38b	8.12±0.60b	8.83±3.00ab	7.27±2.23b	12.82±4.35a	7.38±2.04b	7.24±1.03b
根体积RV （cm³）	0.83±0.07ab	0.49±0.03d	0.57±0.10cd	0.65±0.11bcd	0.76±0.13bc	0.99±0.23a	0.85±0.05ab	0.51±0.07d
各分级根体积RV of each class （cm³）
Ⅰ	0.23±0.04a	0.09±0.01cd	0.12±0.02bc	0.12±0.05bc	0.17±0.05b	0.15±0.01b	0.14±0.02bc	0.04±0.01d
Ⅱ	0.59±0.07a	0.33±0.07cd	0.29±0.10d	0.33±0.07cd	0.43±0.06bc	0.43±0.03bc	0.52±0.06ab	0.27±0.05d
Ⅲ	0.18±0.03b	0.11±0.02b	0.13±0.02b	0.15±0.02b	0.17±0.02b	0.27±0.09a	0.16±0.05b	0.13±0.02b
Ⅳ	0.54±0.17bc	0.36±0.12c	0.61±0.09bc	0.84±0.36ab	0.55±0.19bc	1.03±0.33a	0.61±0.13bc	0.60±0.19bc
平均直径RD （mm）	0.33±0.01e	0.41±0.01d	0.44±0.00cd	0.47±0.07bcd	0.45±0.02cd	0.54±0.07ab	0.50±0.01abc	0.56±0.03a
根尖数RT	1759.67±91.54a	598.33±118.45bc	513.33±74.57c	564.00±190.84bc	723.00±97.15bc	603.33±147.55bc	735.33±53.68b	623.67±46.19bc
分枝数RF	3768.67±659.30a	1111.67±62.77bc	1225.67±282.53bc	1313.67±507.38bc	1578.67±391.95b	1512.33±282.17b	1451.00±178.10b	641.00±142.45c

项目 Item	CK	Cd₅₀
项目 Item	CK	Si₀	Si_0.25	Si_0.5	Si₁	Si_1.5	Si₂	Si₄
总根长RL （cm）	966.95±120.15a	367.71±32.39b	380.44±64.23b	393.17±142.11b	484.58±115.19b	433.66±43.93b	436.79±41.96b	206.38±19.77c
各分级总根长RL of each class （cm）
Ⅰ	794.09±104.54a	266.37±14.84b	290.32±43.70b	290.55±129.39b	358.25±98.33b	297.63±39.49b	284.08±28.68b	115.60±17.26c
Ⅱ	146.80±17.46a	86.01±20.61bcd	67.94±20.62d	79.36±14.49bcd	101.85±14.47b	97.94±5.46bc	130.00±15.51a	71.24±5.93cd
Ⅲ	16.10±2.26b	9.43±1.67c	11.83±2.01bc	13.17±1.46bc	15.30±2.37bc	22.39±7.32a	13.67±4.06bc	10.61±1.19bc
Ⅳ	9.60±3.06b	5.85±1.59b	10.31±0.66b	10.02±2.99b	9.13±2.70b	15.49±5.20a	8.93±3.13b	8.83±0.89b
根表面积SA （cm²）	100.56±10.31a	47.73±3.24de	52.42±8.81cde	56.09±14.61bcd	68.12±13.74bc	72.87±9.37b	68.21±4.97bc	36.29±4.09e
各分级根表面积SA of each class （cm²）
Ⅰ	42.73±5.91a	15.93±0.73b	19.04±2.73b	19.20±8.51b	25.10±7.50b	22.21±2.28b	20.62±2.25b	6.66±1.09c
Ⅱ	32.49±3.91a	18.75±4.14cd	15.48±5.06d	17.75±3.50cd	23.11±3.12bc	22.60±1.28bc	28.80±3.31ab	15.20±2.07d
Ⅲ	6.05±0.87b	3.57±0.59b	4.45±0.78b	4.93±0.53b	5.69±0.82b	8.62±2.93a	5.15±1.56b	4.08±0.48b
Ⅳ	7.43±2.33b	4.68±1.38b	8.12±0.60b	8.83±3.00ab	7.27±2.23b	12.82±4.35a	7.38±2.04b	7.24±1.03b
根体积RV （cm³）	0.83±0.07ab	0.49±0.03d	0.57±0.10cd	0.65±0.11bcd	0.76±0.13bc	0.99±0.23a	0.85±0.05ab	0.51±0.07d
各分级根体积RV of each class （cm³）
Ⅰ	0.23±0.04a	0.09±0.01cd	0.12±0.02bc	0.12±0.05bc	0.17±0.05b	0.15±0.01b	0.14±0.02bc	0.04±0.01d
Ⅱ	0.59±0.07a	0.33±0.07cd	0.29±0.10d	0.33±0.07cd	0.43±0.06bc	0.43±0.03bc	0.52±0.06ab	0.27±0.05d
Ⅲ	0.18±0.03b	0.11±0.02b	0.13±0.02b	0.15±0.02b	0.17±0.02b	0.27±0.09a	0.16±0.05b	0.13±0.02b
Ⅳ	0.54±0.17bc	0.36±0.12c	0.61±0.09bc	0.84±0.36ab	0.55±0.19bc	1.03±0.33a	0.61±0.13bc	0.60±0.19bc
平均直径RD （mm）	0.33±0.01e	0.41±0.01d	0.44±0.00cd	0.47±0.07bcd	0.45±0.02cd	0.54±0.07ab	0.50±0.01abc	0.56±0.03a
根尖数RT	1759.67±91.54a	598.33±118.45bc	513.33±74.57c	564.00±190.84bc	723.00±97.15bc	603.33±147.55bc	735.33±53.68b	623.67±46.19bc
分枝数RF	3768.67±659.30a	1111.67±62.77bc	1225.67±282.53bc	1313.67±507.38bc	1578.67±391.95b	1512.33±282.17b	1451.00±178.10b	641.00±142.45c

项目 Item	Cd处理 Cd treatment （μmol·L^-1）	Si处理 Si treatment （mmol·L^-1）	平均值 Average value	排序 Rank
CK	0	0	0.82	1
Cd₅₀Si₀	50	0	0.31	7
Cd₅₀Si_0.25	50	0.25	0.45	4
Cd₅₀Si_0.5	50	0.50	0.43	5
Cd₅₀Si₁	50	1.00	0.53	2
Cd₅₀Si_1.5	50	1.50	0.49	3
Cd₅ Si₂	50	2.00	0.36	6
Cd₅₀Si₄	50	4.00	0.07	8

项目 Item	Cd处理 Cd treatment （μmol·L^-1）	Si处理 Si treatment （mmol·L^-1）	平均值 Average value	排序 Rank
CK	0	0	0.82	1
Cd₅₀Si₀	50	0	0.31	7
Cd₅₀Si_0.25	50	0.25	0.45	4
Cd₅₀Si_0.5	50	0.50	0.43	5
Cd₅₀Si₁	50	1.00	0.53	2
Cd₅₀Si_1.5	50	1.50	0.49	3
Cd₅ Si₂	50	2.00	0.36	6
Cd₅₀Si₄	50	4.00	0.07	8

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