A Simple and High-Throughput Method for Xylem Sap Collection

Figures & data

Figure 1. Xylem sap collection of small- and medium-volume samples using cotton and tubes.

(A–D) Xylem sap collection of small-volume samples. (A) Items required for small sample collection: plastic straws, absorbent cotton and 1.5-ml tubes. (B) Tube assembly for xylem sap collection. (C) Assembled tubes are placed on cut shoots and the xylem sap is absorbed by the cotton. (D) After xylem sap absorption in cotton, tubes are centrifuged (15,000×g for 2 min). (E) The absorbed xylem sap is separated from the cotton and collected in the bottom of the tubes (arrowhead). (F–J) Xylem sap collection of medium-volume samples. (F) Items required for medium sample collection: absorbent cotton and 2-ml tubes. (G) Assembly for xylem sap collection. (H) Assembled tubes are placed on cut shoots and the xylem sap is absorbed by the cotton. (I) After xylem sap absorption, a hole is made at the bottom of the tube using a pin and the tube is placed in a 5-ml tube. (J) The absorbed xylem sap is separated from the cotton and collected in the bottom of the 5-ml tube via centrifugation (15,000×g for 3 min). The red dashed line represents the maximum volume that can be collected using this medium sample collection method (1 ml).

Figure 2. Cd concentrations in shoots and xylem sap.

Cd concentrations in the shoots (A) and xylem sap collected using the medium sample collection method (B). 5-week-old plants were used for the analysis. 1164-a is an OsHMA3 mutant and Hitomebore is the corresponding wild-type. (A) n = 14; (B) n = 9–14. Mann–Whitney–Wilcoxon test.

*p < 0.05; **p < 0.01.

Table 1. Concentration (ppb) of measured elements in water and xylem sap collected by our medium- and small-scale methods.

Element	Medium-scale method			Small-scale method
	Contamination from the assembly (n = 3)	Xylem sap (rice)		Contamination from the assembly (n = 4)	Xylem sap (sorghum) (n = 110)
		Hitomebore (n = 14)	1164-a (n = 9)
Li	1.21 ± 0.00	2.19 ± 1.10	2.91 ± 2.29	1.98 ± 0.29	9.51 ± 3.98
B	138 ± 37	386 ± 76	405 ± 53	316 ± 350	892 ± 369
Na	5070 ± 130	13,200 ± 8500	18,000 ± 4300	6300 ± 920	10,700 ± 6700
Mg	1300 ± 90	24,200 ± 6800	29,300 ± 6800	1170 ± 300	41,100 ± 20,900
P	962 ± 34	ND	ND	667 ± 82	78,300 ± 51,300
S	ND	ND	ND	ND	24,300 ± 21,000
K	3460	308,000 ± 152,000	374,000 ± 139,000	5520 ± 2020	614,000 ± 317,000
Ca	4810 ± 240	77,400 ± 26,500	83,500 ± 19,400	4970 ± 1030	94,000 ± 45,800
Mn	17.6 ± 5.1	31,600 ± 15,300	28,300 ± 13,600	12.1 ± 1.7	2660 ± 1400
Fe	ND	65.8 ± 43.8	172 ± 111	ND	589 ± 825
Co	ND	3.93 ± 2.01	6.78 ± 1.63	ND	10.7 ± 18.6
Ni	ND	10.7 ± 6.3	17.3 ± 17.1	ND	13.6 ± 16.1
Cu	10.4	66.4 ± 29.6	104 ± 48	ND	324 ± 238
Zn	ND	1110 ± 393	1650 ± 1080	ND	786 ± 587
Ge	ND	1.66 ± 0.53	1.84 ± 0.53	ND	0.274 ± 0.091
As	0.29 ± 0.08	0.317 ± 0.125	0.483 ± 0.243	0.307 ± 0.037	0.412 ± 0.197
Se	ND	ND	ND	ND	ND
Rb	1.98	456 ± 210	558 ± 200	2.32 ± 1.87	131 ± 65
Sr	9.7 ± 1.0	93.8 ± 34.9	115 ± 22	10.1 ± 1.7	135 ± 70
Mo	0.839 ± 0.207	3.79 ± 3.42	3.59 ± 1.75	1.48 ± 0.91	80.7 ± 43.6
Cd	ND	1.03 ± 0.48	2.09 ± 1.04	ND	0.271 ± 0.159
Cs	0.124 ± 0.035	3.05 ± 1.02	3.73 ± 1.06	0.0943 ± 0.0149	1.07 ± 0.49

Mean ± SD (rice data are the same as Figure 2B).

ND: Not detected, lower than detection limit.