Effects of abscisic acid and brassinolide on photosynthetic characteristics of Leymus chinensis from Songnen Plain grassland in Northeast China

Botanical Studies

Table 3 Photosynthetic parameters of L. chinensis in responses to CO ₂ ( C _i ) under ABA and BR treatments

Treatment	A _sat	CCP	*Resp*	V _cmax	J _max	V _TPU	CE
Treatment	[μmol m^–2 s^-1]	CCP	*Resp*	V _cmax	J _max	V _TPU	CE
Control	31.16 ± 3.61 cd¹	30.00a	18.30 ± 1.15c	33.50 ± 2.82de	140.00 ± 2.67e	22.70 ± 1.67c	0.04 ± 0.00c
ABA	27.57 ± 4.25d	30.00a	18.40 ± 1.29c	33.50 ± 2.30de	162.00 ± 2.81d	28.20 ± 1.29b	0.04 ± 0.00c
High BR	31.27 ± 2.56 cd	30.00a	17.20 ± 1.05 cd	34.10 ± 2.64d	191.00 ± 3.11c	32.70 ± 1.87a	0.04 ± 0.00c
ABA + low BR	32.06 ± 3.17c	30.00a	23.10 ± 2.00ab	37.90 ± 2.71c	199.00 ± 3.09c	27.00 ± 1.48b	0.07 ± 0.00b
ABA + medium BR	33.19 ± 3.89c	30.00a	24.60 ± 1.65a	45.20 ± 2.35b	237.00 ± 3.47b	20.40 ± 1.95d	0.13 ± 0.00ab
ABA + high BR	49.51 ± 4.06a	30.00a	25.20 ± 1.45a	51.90 ± 2.88a	262.00 ± 3.55a	25.90 ± 1.55bc	0.15 ± 0.00a
High ABA + high BR	41.93 ± 3.73b	30.00a	20.80 ± 1.82b	51.10 ± 2.63a	236.00 ± 3.17b	32.80 ± 1.73a	0.14 ± 0.00ab

ABA: abscisic acid; BR: brassinolide; A_sat: light-saturated rate of net photosynthesis; CCP: CO₂ compensation point; Resp: respiration; V_cmax: maximum RUBP carboxylation rates; J_max: the maximum electron transport; V_TPU: maximum triose-phosphate utilization; CE: carboxylation efficiency calculated from the data of photosynthetic response to CO₂. ¹ : Different letters with a column indicate significate difference at P ≤ 0.05.