Analysis of factors related to varietal differences in the yield of rice (Oryza sativa L.) under Free-Air CO₂ Enrichment (FACE) conditions

Figures & data

Table 1. Climate condition of Nipponbare with ambient in experiment years.

Year	Mean temperature (°C)		Solar radiation (MJ m^−2 d^−1)
	T-H	H-M	T-H	H-M
2010	24.0 (+1.9)	27.1 (+3.3)	18.7 (+2.5)	18.3 (+3.6)
2011	23.7 (+1.6)	24.7 (+0.9)	17.2 (+1.0)	15.8 (+1.1)

T: transplanting time, H: heading stage, M: maturity. Values in the parenthesis are the difference from the average of 1981–2010.

Table 2. Growth parameters of five rice varieties grown under ambient (AMB) and FACE.

				Aboveground dry weight (g m^−2)		ΔW	NSC FH	ΔW+NSC	ΔW+NSC	Nitrogen uptake (g m^−2)
CO2	Variety	Days to FH (days)	Growth duration (days)	FH	M	(g m^−2)	(g m^−2)	(g m^−2)	ratio	FH	M	Harvest Index
AMB	Koshihikari	69 f	105 g	1070 e	1614 f	544 b	233 f	777 c		10.2 c	12.6 c	0.36 bc
	Nipponbare	78 b	117 d	1137 de	1703 ef	566 b	242 ef	808 bc		11.8 abc	14.3 abc	0.31 c
	Momiroman	77 b	124 a	1199 cde	1741 def	542 b	287 cd	828 bc		12.2 abc	13.9 abc	0.30 c
	Takanari	72 d	113 e	1120 de	1732 def	612 ab	267 def	879 bc		11.7 abc	14.5 abc	0.37 ab
	Hokuriku193	80 a	122 b	1523 b	2118 b	595 b	408 b	1003 ab		14.1 a	15.5 a	0.33 bc
FACE	Koshihikari	66 g	102 h	1214 cde	1806 de	617 ab	267 def	885 bc	(1.14)	10.3 bc	12.9 bc	0.35 bc
	Nipponbare	75 c	113 e	1251 cd	1899 cd	648 ab	282 cde	930 bc	(1.15)	12.3 abc	14.7 ab	0.31 c
	Momiroman	75 c	122 b	1338 c	1996 bc	658 ab	319 c	977 ab	(1.18)	12.7 ab	14.6 ab	0.32 bc
	Takanari	70 e	111 f	1236 cd	2062 bc	826 a	304 cd	1130 a	(1.29)	11.8 abc	15.9 a	0.38 a
	Hokuriku193	79 a	121 c	1687 a	2403 a	716 ab	456 a	1172 a	(1.17)	13.8 a	15.7 a	0.33 bc
AMB	Mean	75	116	1210	1781	572	287	859		12.0	14.1	0.33
FACE	Mean	73	114	1345	2033	693	326	1019		12.2	14.8	0.34
	ratio	(0.97)	(0.98)	(1.11)	(1.14)	(1.21)	(1.13)	(1.19)		(1.02)	(1.04)	(1.02)
ANOVA	Year (A)	**	**	**	ns	ns	**	ns		**	**	ns
	CO2 (B)	**	**	**	**	**	**	**		ns	*	ns
	Variety (C)	**	**	**	**	*	**	**		**	**	**
	A X B	ns	ns	ns	ns	ns	**	ns		ns	ns	ns
	B X C	ns	ns	ns	ns	ns	ns	ns		ns	ns	ns
	C X A	**	**	**	**	ns	**	ns		ns	ns	**
	A X B X C	ns	ns	ns	ns	ns	ns	ns		ns	ns	ns

Data indicate the mean of 2 years with four replications. Days to FH: days from transplanting to the full-heading stage. Growth duration: days from transplanting to the maturity. ΔW: Increase of aboveground dry weight at grain-filling period. NSC: non-structural carbohydrates. Values in parentheses represent the ratio of FACE/AMB. Values within a column followed by the same letter are not significantly different at the 0.05 probability level by Tukey’s test. * and **: significant at the 0.05 and the 0.01 level. ns: not significant by ANOVA. FH: full-heading. M: maturity.

Table 3. Yield and yield components of five rice varieties grown under ambient (AMB) and FACE.

		Rough	Hulled	Hulled		no. of	no. of	1000-grain	Sink	Sink	Sink
		grain yield	grain yield	grain yield	Panicles	spikelet	spikelet	weight	capacity	capacity	filling
CO2	Variety	(g m^−2)	(g m^−2)	ratio	(m^−2)	/panicle	(X 10^3 m^−2)	(g)	(g m^−2)	ratio	(%)
AMB	Koshihikari	859 de	679 de		400 b	93 b	37.1 fg	22.3 cd	829 e		82.5 abc
	Nipponbare	813 e	634 e		413 b	85 b	34.8 g	22.7 bc	790 e		80.3 c
	Momiroman	878 de	655 de		238 e	178 a	42.4 cde	23.7 a	1004 bc		65.2 d
	Takanari	1004 bc	778 bc		282 d	167 a	46.5 bc	20.6 e	956 cd		81.4 bc
	Hokuriku193	1090 b	840 b		258 de	170 a	43.3 cd	22.8 bc	986 cd		85.4 a
FACE	Koshihikari	942 cd	745 cd	(1.10)	425 ab	93 b	39.8 def	22.2 d	885 de	(1.07)	85.0 ab
	Nipponbare	932 cd	729 cd	(1.15)	452 a	85 b	38.2 efg	23.1 b	882 de	(1.12)	82.7 abc
	Momiroman	1085 b	810 bc	(1.24)	276 d	183 a	50.2 b	23.6 a	1188 a	(1.18)	68.7 d
	Takanari	1266 a	970 a	(1.25)	321 c	179 a	57.0 a	20.5 e	1170 a	(1.22)	82.9 abc
	Hokuriku193	1244 a	958 a	(1.14)	283 d	174 a	49.0 b	22.8 b	1117 ab	(1.13)	85.9 a
AMB	Mean	929	717		318	139	40.8	22.4	913		78.9
FACE	Mean	1094	842		351	143	46.8	22.4	1048		81.0
	ratio	(1.18)	(1.17)		(1.10)	(1.03)	(1.15)	(1.00)	(1.15)		(1.03)
ANOVA	Year (A)	ns	ns		**	**	**	**	**		**
	CO2 (B)	**	**		**	ns	**	ns	**		**
	Variety (C)	**	**		**	**	**	**	**		**
	A X B	ns	ns		ns	ns	ns	ns	ns		ns
	B X C	**	**		ns	ns	**	ns	**		ns
	C X A	**	**		**	**	**	**	**		**
	A X B X C	ns	ns		ns	ns	ns	*	ns		ns

Data indicate the mean of 2 years with four replications. Values within a column followed by the same letter are not significantly different at the 0.05 probability level by Tukey’s test. Values in parentheses represent the ratio of FACE/AMB. * and **: significant at the 0.05 and the 0.01 level. ns: not significant by ANOVA. Sink capacity (g m⁻²) = No. of spikelets (m⁻²) × 1000-grain weight (g)/1000. Sink filling rate (%) = 100 × Hulled grain yield (g m⁻²)/Sink capacity (g m⁻²).

Figure 1. Effects of sink capacity and source accumulation on the change of yield under FACE condition.

Notes: Sink capacity (g m⁻²) = No. of spikelet (m⁻²) × 1000 grain weight (g)/1000. ΔW: Increase of aboveground dry weight at grain-filling period. NSC: non-structural carbohydrates at full-heading stage.

Table 4. Increase of aboveground dry weight and sink capacity in FACE, and sink production efficiency.

			Sink production efficiency
	Difference (FACE-AMB)		Sink capacity/Aboveground dry weight (g g^−1)		Sink capacity/Nitrogen uptake (g g^−1)
Variety	Aboveground dry weight (g m^−2)	Sink capacity (g m^−2)	AMB	FACE	AMB	FACE
Koshihikari	120	56 d	0.77 ab	0.73 b	81.4 a	85.7 abc
Nipponbare	114	91 cd	0.70 bc	0.71 b	67.2 b	71.9 c
Momiroman	114	184 ab	0.82 a	0.89 a	82.1 a	93.1 ab
Takanari	116	214 a	0.85 a	0.95 a	81.9 a	99.9 a
Hokuriku193	164	131 bc	0.65 c	0.67 b	70.1 ab	81.0 bc
Mean	126	135	0.76	0.79	76.5	86.3
CO2 (A)	-	-	ns		**
Variety (B)	ns	**	**		**
A × B	-	-	*		ns

Data indicate the mean of 2 years with four replications. Values of aboveground dry weight and nitrogen uptake are those at full-heading. Values within a column followed by the same letter are not significantly different at the 0.05 probability level by Tukey’s test. * and **: significant at the 0.05 and the 0.01 level. ns: not significant by ANOVA. Values with underline are significantly larger sink production efficiency in FACE than AMB at the 0.05 probability level by t-test.