TABLE 1.

Effect of planting density and nitrogen application on vascular bundle area of maize at milking stage in 2016.

Position	Planting density	N level	The average area of single big vascular bundle (×10–3 mm2)			The average area of single small vascular bundle (×10–3 mm2)			TAVB	PBVB	PSVB
			Sum	Phloem	Xylem	Sum	Phloem	Xylem	(mm2)
Basal-stem	ND	N0	63.1d	7.3c	26.4c	48.8c	2.4b	11.7b	33.7d	0.30c	0.70a
		N150	89.9bc	9.3b	32.3b	62.9a	2.5b	10.3b	49.8b	0.30c	0.70a
		N300	122.6a	13.5a	49.8a	63.8a	3.4a	15.6a	61.9a	0.37b	0.63b
	HD	N0	79.0cd	5.4c	31.0b	47.2c	2.3b	9.7b	33.0d	0.34b	0.66b
		N150	97.3b	6.0c	29.8bc	48.2c	2.6bc	9.4b	41.1c	0.42a	0.58c
		N300	135.4a	13.1a	51.0a	53.0b	2.3b	14.4a	53.5b	0.44a	0.56c
Ear-located	ND	N0	59.8c	5.3c	17.4c	40.4b	1.7b	6.9a	20.3d	0.41bc	0.59ab
		N150	77.1b	5.9bc	17.0c	40.8b	2.2a	7.1a	24.2c	0.44bc	0.56ab
		N300	89.0a	8.2a	20.9a	46.3a	2.2a	7.5a	33.0a	0.45b	0.55b
	HD	N0	76.9b	6.1bc	13.2d	37.1c	0.5c	5.3b	16.1e	0.56a	0.44c
		N150	83.0ab	6.5b	19.8ab	42.6b	2.0ab	6.8a	22.4cd	0.44bc	0.56ab
		N300	85.3a	6.9b	18.1bc	46.2a	2.1ab	7.0a	28.5b	0.40c	0.60a
Peduncle	ND	N0	83.3cd	13.7d	23.3d	24.1c	2.2c	4.6c	13.7d	0.58b	0.42c
		N150	77.3d	15.2cd	26.5c	24.2c	2.6bc	4.7c	17.3c	0.49c	0.51b
		N300	109.3a	18.6b	30.0b	45.9a	3.5a	6.8a	32.8a	0.45d	0.55a
	HD	N0	85.7bc	18.2b	22.6d	19.2d	2.1c	4.2c	12.9de	0.68a	0.32d
		N150	92.6b	17.0bc	28.9bc	22.3c	2.4c	4.8c	12.3e	0.59b	0.41c
		N300	113.7a	21.4a	41.7a	39.7b	3.1ab	6.1b	29.8b	0.52c	0.48b
Cob	ND	N0	82.8d	12.7c	29.8b	22.3e	2.9c	6.3c	7.6c	0.73a	0.27c
		N150	152.7b	17.3b	41.6a	47.3b	3.5bc	6.8bc	17b	0.69b	0.31b
		N300	169.6a	19.6b	45.1a	58.6a	4.6ab	8.1a	24.5a	0.65c	0.35a
	HD	N0	121.2c	19.1b	22.7c	21.7e	2.8c	6.2c	8.5c	0.76a	0.24c
		N150	144.5b	18.1b	44.7a	28.1d	3.3bc	7.5ab	9.6c	0.69b	0.31b
		N300	176.7a	23.6a	43.0a	44.7c	4.0b	7.2b	17.9b	0.66bc	0.34ab

TAVB, total area of vascular bundle; PBVB, proportion of big vascular bundle area to total vascular bundle area; PSVB, proportion of small vascular bundle area to total vascular bundle area. ND and HD indicate planting density of 67,500 and 90,000 plants ha^–1; N0, N150, and N300 indicate N applied at 0, 150, and 300 kg ha^–1 levels, respectively. Values of six treatments followed by different letters indicate significant difference at 5% level.