Table 1.

Comparison of deuterium ion counts (μm⁻²) of each tissue under high (during the day), less (sunset) and no (night period) evaporative demand

	Vessel		Cortex	Cambium	Parenchyma		Control
	Xylem	Phloem			Xylem	Phloem
Day	8.04±0.56 a	4.65±0.45 b	4.32±0.40 b	4.05±0.44 b	1.25±0.07 c	0.89±0.07 c
Sunset	13.61±0.79 a	1.94±0.22 c		4.33±0.56 b	1.45±0.08 c	1.65±0.13 c	0.13±0.02
Night	13.25±0.27 a	2.87±0.37 b		3.64±0.47 b	1.60±0.11 c	1.78±0.14 c

D₂O labelling was done for 1 h during a sunny morning (9:00–10:00 h) inside an open glasshouse for high evaporative demand in experiment 1. In experiment 2, D₂O labelling was done for 4 h (13:00–17:00 h for sunset sampling) and 8 h (13:00–21:00 h for night sampling) in a growth chamber. The values are expressed as the average number of deuterium ion counts per 1 μm² of cells in each tissue. The control shows the mean of each tissue with unlabelled H₂O.

Each value is shown as the average ±SE. The same letter within each row indicates no significant statistical difference at the 5% level by Fisher's PLSD with 4–8 replicate measurements.