Relationship between leaf chlorosis and different boron forms in Trifoliate orange seedlings under excessive boron supply

Figures & data

Figure 1 Classification of leaf chlorosis (“None” indicates the normal leaf without chlorosis; “I” indicates the first level of leaf chlorosis: the leaf tip was slightly chlorotic; “II” indicates the second level of leaf chlorosis: the leaf tip was completely chlorotic; “III” indicates the third level of leaf chlorosis: the chlorosis along the margins has expanded and the leaves were necrotic).

Table 1 Effects of different boron (B) treatments on the seedling height (cm), leaf numbers and dry weight (leaf, stem, root, total) (g) (mean ± standard error, SE)

			Dry weight (g)
Treatment	Seedling height (cm)	Leaf numbers	Leaf	Stem	Root	Total
B5	30.1 ± 1.7a	29 ± 3a	0.36 ± 0.01a	0.30 ± 0.03a	0.61 ± 0.05a	1.26 ± 0.08a
B10	24.9 ± 0.6a	26 ± 3a	0.34 ± 0.02ab	0.30 ± 0.01a	0.56 ± 0.04a	1.20 ± 0.04a
B20	25.8 ± 4.4a	24 ± 5a	0.27 ± 0.03ab	0.19 ± 0.05a	0.55 ± 0.05a	1.01 ± 0.08ab
B100	20.7 ± 2.0a	22 ± 2a	0.26 ± 0.01b	0.17 ± 0.02b	0.35 ± 0.01b	0.78 ± 0.03b

Different letters following the means indicate significant differences at P < 0.05 by Tukey’s test (n = 3).

Table 2 The proportion of different chlorotic levels in chlorotic leaves of different boron (B) treatments (%) (mean ± standard error, SE)

Treatment	I	II	III	Total
B5	11.8 ± 1.6	0	0	11.8 ± 1.6c
B10	26.7 ± 4.9	0	0	26.7 ± 4.9bc
B20	12.0 ± 2.0	22.3 ± 3.2	0	34.2 ± 4.5ab
B100	25.1 ± 2.7	7.6 ± 1.8	15.0 ± 1.4	47.7 ± 2.3a

Different letters following the means indicate significant differences at P < 0.05 by Tukey’s test (n = 3).

Figure 2 Boron (B) concentration of the root, stem, new leaves (N-Leaf) and old leaves (O-Leaf) between different B treatments. Different letters indicate significant differences at P < 0.05 by Tukey (n = 3). DW, dry weight.

Figure 3 Boron (B) forms (free B, semi-bound B, bound B) in (a) root and (b) stem (mean ± standard error, SE). FW, fresh weight.

Table 3 Free boron (B) in different chlorotic leaves with different treatments (mg kg^–1 fresh weight, FW) (mean ± standard error, SE)

	B5	B10	B20	B100
None	9.6 ± 0.1f	11.7 ± 1.4f	18.3 ± 0.2ef	24.1 ± 0.3ef
I	32.2 ± 1.2de	30.8 ± 0.7de	43.7 ± 1.5cd	42.6 ± 2.1cd
II			53.4 ± 1.3c	78.3 ± 2.1b
III				141.9 ± 9.4a

Different letters indicate significant differences at P < 0.05 by Tukey’s test (n = 3).

Table 4 Semi-bound boron (B) in chlorottic leaves of different treatments (mg kg^–1 fresh weight, FW) (mean ± standard error, SE)

	B5	B10	B20	B100
None	6.4 ± 0.6d	7.9 ± 0.5d	11.4 ± 1.7cd	12.3 ± 0.4cd
I	21.5 ± 4.2bc	20.0 ± 0.5bc	21.8 ± 1.1bc	26.0 ± 2.3ab
II			27.2 ± 3.3ab	34.1 ± 2.3a
III				33.4 ± 2.9a

Different letters indicate significant differences at P < 0.05 by Tukey’s test (n = 3).

Table 5 Bound boron (B) in chlorotic leaves of different treatments (mg kg^–1 fresh weight, FW) (mean ± standard error, SE)

	B5	B10	B20	B100
None	10.9 ± 0.9d	13.0 ± 1.5bcd	12.6 ± 1.8cd	12.1 ± 0.9cd
I	25.8 ± 3.4a	26.3 ± 2.6a	24.9 ± 3.0ab	23.5 ± 2.7abc
II			25.7 ± 0.9a	22.5 ± 2.9abcd
III				21.9 ± 3.5abcd

Different letters indicate significant differences at P < 0.05 by Tukey’s test (n = 3).

Figure 4 Different forms of boron (B) in different level leaves (data in the figure are the means of B concentrations in different treatments). FW, fresh weight.