Root development and the expression of aquaporin genes in rice seedlings under osmotic stress

Figures & data

Figure 1. Two types of lateral root, e.g. root of Puluik Arang under 10% PEG treatment.

Table 1. Water uptake, dry matter production and root morphological traits of two rice cultivars in response to PEG stress.

Cultivar	Treatment	Water uptake (mg plant^−1 h−1)	Shoot DW (mg plants^−1)	Root DW (mg plants^−1)	Total root length (cm plant^−1)	Root surface area (cm^2 plant^−1)	S type lateral root number (plant^−1)	L type lateral root number (plant^−1)	Water uptake/root length (mg cm^−1 h^−1)
Puluik Arang	Control	169a	26.5ab	4.9a	255a	12.8a	843a	20b	0.66a
	10% PEG	172a	28.1a	4.9a	250a	13.6a	781a	36a	0.69a
	20% PEG	86b	19.9b	4.3a	233a	11.8a	854a	37a	0.37b
Akitakomachi	Control	152a^ns	23.9a^ns	4.6a^ns	312a*	16.3a*	1231a*	8b*	0.49a*
	10% PEG	121a*	22.5a*	4.7a^ns	288ab*	15.3a*	1099ab	14a*	0.42a*
	20% PEG	50b^ns	17.4b^ns	4.2a^ns	258b^ns	12.5b^ns	1035b*	15a*	0.20b*

Notes. Measurements of water uptake (n = 3) were conducted in 13-day-old plants from 3 to 4 h after lights-on. Dry matter weight (n = 3) and root morphological traits (n = 10) of 13-day-old plants were measured. The amount of water uptake per unit root length was calculated by dividing water uptake amount from 3 h to 4 h after lights-on by average root length. Values followed by a different letter within each cultivar indicate significant difference at p < 0.05 by Tukey’s test. Asterisk indicates significant difference between the cultivars ‘Puluik Arang’ and ‘Akitakomachi’ under each treatment by t-test (p < 0.05), and ns = not significant.

Figure 2. Comparison of the copy numbers of expressed aquaporin genes in the seminal roots and lateral roots emerged from seminal root of different cultivars under osmotic stress. Roots of 13-day-old plants were sampled three hours after lights-on. Three replicates of each cultivar for each treatment were conducted using different plant samples. Bars indicate the standard error (n = 3). Asterisk represents a significant difference between cultivars (p < 0.05, t-test). Probability from the results of ANOVA was shown to determine the individual and interaction effects of the treatment and cultivar.

Figure 3. Immunolocalization of OsTIP2;1 in seminal root tissue of the cultivar ‘Puluik Arang’ subjected to 10% PEG treatment. Root tissue samples from 13-day-old plants were excised from the lateral root initiation zone (approximately 1–2 cm from the root tip) and from the mature zone (middle position of seminal root) of the seminal root. Bars represent 100 μm.

Table 2. Correlation coefficients between the expression levels of 11 aquaporin genes versus the amount of water uptake and the amount of water uptake per unit root length.

Aquaporin gene	vs. Water uptake	vs. Water uptake per unit root length
OsPIP1;1	0.937**	0.907*
OsPIP1;2	0.807*	0.847*
OsPIP1;3	0.676^ns	0.777^ns
OsPIP2;1	0.894*	0.959**
OsPIP2;2	0.877*	0.956**
OsPIP2;3	0.866*	0.771^ns
OsPIP2;5	0.881*	0.951**
OsPIP2;6	0.004^ns	0.130^ns
OsTIP1;1	0.907*	0.836*
OsTIP2;1	0.714^ns	0.850*
OsTIP2;2	0.392^ns	0.251^ns

Note. Data of the two cultivars and three water treatments were combined for calculation of the coefficients.

*p < 0.05; **p < 0.01; ***p < 0.001, ns = not significant.