Tolerance and adaptation characteristics of sugar beet (Beta vulgaris L.) to low nitrogen supply

Figures & data

Figure 1. Growth and phenotype of nine sugar beet genotypes under LN stress. Low nitrogen (LN): 0.5 mmol·L⁻¹ N; CK: 10 mmol·L⁻¹, the same key applies to other figures and tables.

Figure 2. Effect of LN on the root morphology of the nine sugar beet genotypes.

Figure 3. Morphological changes in the nine sugar beet genotypes under low nitrogen treatment. (a) Hypocotyl diameter, (b) plant height, (c) root length, (d) total root surface, and (e) leaf area. Lowercase letters indicate a significant difference between each genotype at the same nitrogen supply level (p < .01), as analyzed by Duncan’s multiple tests. The same key applies to other figures.

Figure 4. Changes in chlorophyll a content (a), chlorophyll b content (b), chlorophyll content (c), Chl a/b (d) and soluble protein (e) in different sugar beet genotypes under low nitrogen treatment.

Figure 5. Biomass of different genotypes under low nitrogen treatment. (a) Leaf fresh weight, (b) root fresh weight, (c) leaf dry weight, (d) root dry weight, and (e) root to shoot ratio.

Figure 6. Distribution characteristics of N in nine genotypes under different nitrogen supply levels. (a) N content in leaves; (b) N content in roots.

Figure 7. Low nitrogen tolerance of nine sugar beet genotypes by Pearson correlation coefficient (r) analysis. Hypocotyl diameter: HD; Plant height: PH; Root length: RL; Total root surface: TRS; Leaf area: LA; Chlorophyll a: Chl a; Chlorophyll b: Chl b; Chlorophyll content: Chl; Chl a and b ratio: Chl a/b; Soluble protein: SP; Leaf fresh weight: LFW; Root fresh weight: RFW; Leaf dry weight: LDW; Root dry weight: RDW; Root-to-shoot ratio: RSR; Leaf N accumulation: LNA; and Root N accumulation: RNA. The same abbreviations are used below. All the data were based on the ratio of N deficiency to N sufficiency. Scale: the bright blue to bright red colors represent negative and positive correlations, respectively. *: P < .05, **: P < .01.

Table 1. Variation coefficient of LN tolerance-related growth characteristics in nine sugar beet genotypes.

	LN				CK				CV(LN)-CV(CK)
	Average	Variation range	SD	CV(LN)	Average	Variation range	SD	CV(CK)
HD	4.780	0.019–0.199	0.385	8.046	7.021	0.028–0.105	0.388	5.521	2.525
PH	13.048	0.017–0.099	0.531	4.068	18.917	0.010–0.104	0.745	3.940	0.127
RL	28.672	0.011–0.157	1.609	5.610	28.736	0.022–0.096	1.743	6.067	−0.457
TRS	284.391	0.013–0.211	34.710	12.205	507.747	0.031–0.290	64.216	12.647	−0.442
LA	111.763	0.024–0.170	11.838	10.592	307.690	0.047–0.272	33.130	10.767	−0.176
Chl a	0.185	0.009–0.174	0.021	11.287	0.373	0.036–0.181	0.040	10.701	0.586
Chl b	0.092	0.049–0.231	0.011	11.544	0.174	0.044–0.315	0.026	14.670	−3.126
Chl	0.277	0.003–0.052	0.031	11.031	0.547	0.006–0.188	0.056	10.191	0.841
Chl a/b	1.999	0.037–0.167	0.140	7.022	2.248	0.041–0.182	0.281	12.491	−5.469
SP	198.671	0.005–0.099	8.323	4.189	319.209	0.004–0.076	9.591	3.005	1.184
LFW	4.035	0.042–0.153	0.447	11.090	10.365	0.030–0.202	0.813	7.846	3.244
RFW	1.725	0.049–0.220	0.187	10.836	3.583	0.063–0.259	0.422	11.775	−0.939
LDW	0.662	0.097–0.414	0.157	23.713	1.177	0.055–0.367	0.235	20.005	3.708
RDW	0.140	0.025–0.234	0.020	14.619	0.246	0.389–1.008	0.032	13.195	1.424
RSR	0.469	0.029–0.337	0.055	11.693	0.348	0.897–1.851	0.034	9.862	1.831
LNA	9.656	0.028–0.391	2.097	21.717	38.252	0.079–0.330	5.070	13.254	8.464
RNA	3.502	0.045–0.173	0.411	11.743	11.636	0.080–0.324	2.111	18.145	−6.402

SD, standard deviation; CV, coefficient of variance.

Table 2. PCA and comprehensive evaluation of the nine sugar beet genotypes.

Variety	Sugar beet genotypes	F1	F2	F3	F4	D value	Sequence
A	94004–2	−0.102	0.536	0.165	−0.053	0.547	4
B	92008 feng	−0.072	0.184	0.219	0.083	0.414	7
C	92008–1	0.175	0.266	0.013	−0.030	0.424	6
D	92017/1-4	0.007	0.231	0.027	−0.023	0.242	8
E	92021-1-1	0.208	0.249	0.013	0.080	0.549	3
F	780016B/12 superior	0.774	0.504	0.144	0.032	1.454	1
G	92011	−0.105	0.024	0.132	−0.029	0.023	9
H	92017/1-8	0.158	0.133	0.072	0.068	0.431	5
I	92015-2-3	−0.303	0.749	0.063	0.051	0.559	2

Figure 8. Changes in the physiological activity of LN-tolerant and LN-sensitive sugar beets under different nitrogen supply levels. (a) SOD activity, (b) POD activity, (c) CAT activity, (d) APX activity, (e) MDA content, and (f) proline content. Lowercase letters indicate a significant difference between each germplasm and nitrogen supply level (p < .01).