Dipotassium tetraborate

Toxicity to terrestrial plants

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to terrestrial plants: long-term

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study is well documented

Qualifier:

no guideline followed

Principles of method if other than guideline:

no guideline was reported

GLP compliance:

not specified

Species:

other: Capsicum annuum L.

Plant group:

other: eudicots

Details on test organisms:

- Common name: pepper
- Source of seed: cv. Nokkwang
- Seed treatment: seeds were sown in washed, fine sand watered with half strength Hoagland's solution.

Test type:

seed germination/root elongation toxicity test

Study type:

laboratory study

Substrate type:

natural soil

Total exposure duration:

3 wk

Test temperature:

4 °C

Details on test conditions:

TEST SYSTEM
- Test container (type, material, size): Wagner pot containing 1 kg of dried sandy loam soil.
- Structure: experiment was structured following a randomized complete block design (RCBD)
- Fresh leaves were put immediately into a liquid N deep-freeze (-70 °C) to analyze antioxidative enzymes
- To analyze mineral elements, plant materials were first air-dried at 70 °C to constant weight.
- Boron analysis was determined spectrophotometrically by the azomethine-H method
- No. of replicates per treatment group: 4 replicates of each treatment


SOURCE AND PROPERTIES OF SOIL
- pH: (1:5 water): 6.0
- EC: 0.45 dS/m
- Organic matter: 8 g/kg
- Total nitrogen: 0.7 g/kg
- Soil texture (if natural soil): dried sandy loam soil
- CEC: Ca 3.8, K 0.5, Na 0.4 cmol+/kg and B 1.0 cmol+/kg
- Pretreatment of soil: a basal fertilizer was applied N-P-K: 100-80-50 kg/ha


GROWTH CONDITIONS
- Photoperiod: natural light conditions
- Germination: in a greenhouse, with daytime temperature of 25 °C an relative humidity 65-70 %. After the second true leaves appeared, the seeds were transplanted.
- Harvest: all plants were harvested 3 weeks after transplanting.

Nominal and measured concentrations:

combination 2 salinity (NaCl at 3 and 6 dS/m) and 2 boron levels (15 and 30 mg/lg H3BO3) + controls

Species:

other: C.annuum

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

>= 5.25 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

B

Basis for effect:

other: dry matter yield

Details on results:

- The toxic effect of salinity was greater in the presence of B, the maximum reduction occured with the combination of 5 dS/m and 30 mg/kg B

Reported statistics and error estimates:

all data were analyzed statistically by analysis of variance using Costat software (CoHort software, Monterey, USA). Means comparisons were conducted using an ANOVA protected the least significant difference (p<0.05)

Conclusions:

No effect of H3BO3 on dry matter yield of hot pepper after 21 days of exposure at normal salinity.

Reference 2

Endpoint:

toxicity to terrestrial plants: long-term

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study is well documented

Qualifier:

no guideline followed

Principles of method if other than guideline:

no guideline was reported

GLP compliance:

not specified

Remarks:

No data is available on the GLP compliance, as no guideline was followed this value was set to no, respectively.

Species:

Triticum aestivum

Plant group:

Monocotyledonae (monocots)

Details on test organisms:

- Common name: Wheat
- Variety: Gerek-79

Test type:

seed germination/root elongation toxicity test

Study type:

laboratory study

Substrate type:

natural soil

Total exposure duration:

60 d

Details on test conditions:

TEST SYSTEM
- Testing facility: greenhouse under natural light conditions
- Test container (type, material, size): grown in plastic pots containing 2000 g air-dried soils
- Method: randomized factorial experiment
- No. of seeds per container: 12 seeds per pot. After emergence, the plants were thinned to 8.
- No. of replicates per treatment group: 4
- 60d after sowing, vegetative growth was harvested and divided into shoot and rot. Samples were washed with boron free distilled water and fresh leaf samples were taken for determination of boron concentrations on cell wall: remaining shoot and root plant samples were dried at 65 °C and weighted. After grinding plant samples were dry-ashed at 500 °C for total plant boron determination by using ICP-OES. Tips of leaves (2 cm length) was taken from each individual plant leaf. Cell wall was separated from the plants. The samples were dried and ashed at 500°C for cell wall boron by using ICP-OES.


SOIL PROPERTIES
- Texture: clay loam
- CaCO3: 46 g/kg
- pH: 8.08
- EC: 0.102 dS/cm
- OM: 10.4 g/kg
- Basal fertilizer were applied to all pots before sowing

Nominal and measured concentrations:

0, 5, 10, 20 mg B/kg as boric acid H3BO3

Species:

Triticum aestivum

Duration:

60 d

Dose descriptor:

NOEC

Effect conc.:

5 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

B

Basis for effect:

growth

Remarks:

shoot and root

Remarks on result:

other: normal Ca concentration

Details on results:

- inhibitory effect of boron on the shoot and root growth was reduced by the presence of calcium

Reported statistics and error estimates:

data obtained from different analyses and measurements were analyzed statistically using Minitab package program (release 10.51) and treatment means were compared using the MSTAT package program (version 3.00) for Duncan's Multiple Range Test.

Conclusions:

the 60d NOEC of boric acid on shoot and root groth of Triticum aestivum is 5 mg/kg B at normal Ca concentrations of the soil.

Description of key information

All selected NOEC/EC₁₀ values from long term single-species toxicity tests with higher plants are summarised in the respective table listing effects to terrestrial plants. All these values are considered reliable (Klimisch score 1 and 2) and relevant for the effects assessment. Thereby all data are based on added doses (nominal or measured), as background concentrations are not always available and the added risk approach will be followed because of the significant difference in bioavailability between boron naturally present in soils and added soluble B. In total 192 individual high quality NOEC/EC₁₀ values (for 28 different species) are selected for the PNEC derivation, ranging from 3 mg B/kg for barley root elongation in Zwijnaarde soil (Van Laer et al., 2010) to 84.0 mg B/kg for wheat shoot length, canola shoot yield and western wheatgrass root yield (Aquaterra, 1998). A large number of papers were assessed from the literature, yet only a limited toxicity dataset could be created due to the poor quality of most of the data.

 

Please also refer to read-across statement section 13.