Botanical Studies

An International Journal

Impact Factor 1.159

Botanical Studies Cover Image
Open Access

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

Botanical StudiesAn International Journal201354:42

DOI: 10.1186/1999-3110-54-42

Received: 22 September 2011

Accepted: 2 April 2013

Published: 2 October 2013

Abstract

Background

It has been well demonstrated that plant growth regulators have important functions in multiple physiological processes. ABA and BR play crucial roles in response of crops to stresses. Photosynthetic capacity of Leymus. chinensis treated by various concentrations of ABA and BR in combination was determined. Further more, the mechanisms of ABA and BR treatments and potential for recovery of saline-alkali grasslands were discussed.

Results

Abscisic acid (ABA) and brassinolide (BR) affected leaf gas exchange, growth and biomass of L. chinensis. The application of ABA and BR mixtures, especially that of 0.01 mM ABA and 2 × 10-4 mM BR, increased the net photosynthetic rate, stomatal conductance, water use efficiency, the maximum net photosynthetic rate, light-saturated rate, leaf respiration rate, the maximum RUBP carboxylation rate, the maximum electron transport rate, the maximum triose-phosphate utilization, carboxylation efficiency and the quantum efficiency of PSII and subsequently enhanced density, height and biomass in L. chinensis. We also observed reduction in the light compensation and saturation points following the application of ABA and BR treatments.

Conclusions

We concluded that proper use of plant growth regulators can enhance the plant growth and productivity on the Songnen grassland, which is particularly important for the improvement of saline – alkaline grassland and the yield of grazing lands.

Keywords

Abscisic acid Brassinolide Leymus chinensis Photosynthetic characteristics Songnen plain grassland

Background

It has been well demonstrated that plant growth regulators are involved in multiple physiological processes Krouk et al. (2011). Plant growth regulators are increasingly used for the improvement of plant growth and stress resistance. Recent publications reported the effects of several resistance-related hormones, including salicylic acid, jasmonates, polyamines, and 5-aminolevulinic acid (ALA), etc. on plant physiological activities. As the most studied stress-responsive hormone, abscisic acid (ABA) play crucial roles in response of plants to abiotic stresses such as drought, salinity and frost Wu (2010). For the water-stressed plants, ABA can decrease water loss via transpiration, improve the antioxidant enzymes system, and induce the expression of stress-related genes. Moreover, exogenous application of ABA significantly influences leaf photosynthesis and photosynthate accumulation through regulating stomata openness and/or activities of photosynthetic enzymes. ABA treatments show complex effects on leaf photosynthesis. Šafránková et al. (2007) found that ABA treatment significantly decreased the net photosynthetic rate (PN) and transpiration rate (E) of the water-stressed barley. ABA associated decrease in PN was also be found in Stylosanthes guianensis Zhou et al. (2006) and Pennisetum typhoides Sankhla and Huber (1974). However, several studies showed positive effects of ABA treatment on leaf photosynthesis McLaren and Smith (1977; Jia and Lu 2003; Li et al. 2006). The compromise results were also be found by Mawson et al. (1981), and Franks and Farquhar (2001). The above mentioned inconsistent results about the effects of ABA on leaf gas exchange may be caused by multiple factors, including differences in stress factors, ABA dosage and treatment time McLaren and Smith (1977).

In addition to the inconsistent effects of plant hormone on plant growth performance, the mixture of different plant hormones can produce additive action or counteraction on plant metabolism Peleg and Blumwald (2011). For example, Sankhla and Huber (1974) found that the mixture of abscisic and gibberellic acids tended to antagonize each other in incorporation of 14CO2 into photosynthetic products. Brassinolide (BR), another common plant hormone with high biological activity, is found recently in vegetables Khripach et al. (2000). BR treatments have significant effects on plant growth and stress resistance Bajguz and Hazat (2009). BR treatments lead to the increase of net photosynthetic rates Vardhini and Ramr (1998 Hou and Li 2001) or delay the reduction of photosynthetic rate Liu et al. (2008). However, the information on the influence of ABA and BR in combination on leaf photosynthesis is less available.

To date, most studies about ABA and BR are mainly focussed on crops with very few studies on perennial grasses. Leymus chinensis, a perennial grass, is the dominate species in the salinized Songnen grassland in Northeastern China Li and Zheng (1997). The Songnen grassland covers approximately 20–25% of the total area in Songnen plain and is mainly utilized for hay production and livestock grazing Li and Zheng (1997). The present study was conducted over three years within self-sown L. chinensis populations. Photosynthetic capacity of L. chinensis treated by various concentrations of ABA and BR in combination was determined. Furthermore, the mechanisms of ABA and BR treatments and potential for recovery of saline-alkali grasslands were discussed.

Methods

Study site and experimental design

This research was conducted at The Grassland Ecosystem Experimental Station of Northeast Normal University, Chang Ling Horse Breeding Farm in Jilin Province (44°30′ to 44°45′N, 123°31′ to 123°56′E), Northeast China. The study area has a typical mesothermal monsoon climate, with an altitude of 37.8 to 144.8 m. The region is cold and dry in spring with frequent wind, warm and wet in summer with frequent drought, early frosts in autumn, and long, cold winters with little snowfall. The mean annual temperature is 5.0°C with a frost–free period of 136 to 146 d. The mean annual precipitation is about 450 mm mainly occured from June to August and accounts for over 60% of the annual precipitation. The annual evaporation is 2 to 3 times higher than precipitation. Salinized meadow soil is the main soil type in the Songnen grassland.

Seven plots were selected for sampling. Each plot area was 10 × 10 m with a 2 m isolation belt between plots. The L. chinensis community in the selected area had been established for two years by artificial seeding. The plants of L. chinensis were uniform in size with almost no weeds. Seven treatments were applied (Table 1).
Table 1

Experimental treatments

Treatment

Concentration(mM)

Control

——

ABA

0.01

High BR

2 × 10-4

ABA + low BR

0.01, 0.02 × 10-4

ABA + medium BR

0.01, 0.2 × 10-4

ABA + high BR

0.01, 2 × 10-4

High ABA + high BR

0.1, 2 × 10-4

ABA: abscisic acid; BR: brassinolide.

ABA and BR were sprayed during the middle ten days of May in 2005 and 2006, respectively. Fully expanded leaves of plants from each plot were used to measure photosynthetic characteristics. The density, height, and biomass of the L. chinensis community were determined using standard sampling methods Shi and Guo (2006), and each measurement was repeated 5 times.

PN, gs, Ci/Ca, and E were determined using a portable open flow gas exchange system LI–6400XT (LI-COR, USA) at 2 h intervals from 8:00 h to 16:00 h. WUE was calculated as PN/E. The photosynthetically active radiation (PAR) was 1000 ± 12 μmol m-2 s-1, CO2 concentration was 350 ± 2 ppm, and leaf temperature was 26.0 ± 0.8°C. Gas exchange was measured on fully expanded leaves from the same adult plants for five plants per plot. Measurements were repeated three times for each selected plant. Moreover, measurements were done within three consecutive days in mid-July.

The responses of photosynthesis to light (A/Q)

For the measurement of A/Q, the photosynthetic photon flux density levels used for the construction of light response curves were: 2000, 1800, 1600, 1400, 1200, 1000, 800, 600, 400, 200, 100, 50 and 0 μmol m-2 s-1 generated by a LI-6400/02B red/blue light source Wu et al. (2007). The CO2 concentration was kept at 380 μmol mol-1 Wang and Zhou (2004). Each measurement was repeated 10 times between 9:00 h to 12:00 h in mid-July. All A/Q parameters were determined by fitting data to the quadratic equation described by Prioul and Chartier (1997). QE, LCP, LSE, Amax were modeled using the linearization of A/Q curves (Long and Bernacchi 2003).

The responses of photosynthesis to CO2(A/Ci)

The same process used in A/Q measurements was used for A/Ci curves. A range of CO2 concentrations (C i ), i.e. 1800, 1600, 1400, 1200, 1000, 800, 600, 400, 200, 100 and 50 μmol mol-1 was generated using a 12 g CO2 cylinder, starting from 1800 and ending at 50 μmol mol-1. The A/Ci curves were measured under four light gradients: 1200, 1000, 800 and 400 μmol m-2 s-1Dordas and Sioulas (2007). Leaf temperature was kept at 32 ± 0.8°C and each gradient of light or CO2 concentration treatment was repeated five times between 9:00 h and 10:00 h. Asat, CCP, Resp, Vcmax, Jmax, VTPU and CE were calculated according to Prioul and Chartier (1997) and Olsson and Leverenz (1994). Leaves were held in the chamber until values of photosynthesis reached a steady state. At CO2 concentration, the analysis of photosynthetic response to CO2 Field et al. (1989, Chen et al. 2006) was accompanied by a match. A model curve described by the rectangular hyperbola Olsson and Leverenz (1994) was fitted.

Chlorophyll fluorescence

Chlorophyll fluorescence measurements included initial fluorescence (Fo), maximum fluorescence (Fm) and variable fluorescence (Fv). Fo refers to fluorescence when PSII reaction center opens entirely. The decrease of Fo indicates the increase of antenna hot dissipation; and the increase of Fo indicates the uneasy reversing damage of PSII reaction center. Fm refers to fluorescence when PSII reaction center closes entirely. A decrease in Fm indicates inhibition of photosynthesis. Fv, the difference between Fm and Fo, reflects a reduction in QA. The first fully expanded, healthy leaves were measured using Li–6400XT (LI-COR, USA) for dark-acclimated and light- acclimated measurements. Fo was measured after 20 min of dark acclimation during a low intensity pulsed. Fm was recorded in a 0.8 s pulse of saturating light (6500 μmol m-2 s-1).

Statistical analyses

All photosynthetic parameters were analyzed using SPSS (v. 11.0 for Windows, USA) and SigmaPlot 10. Photosynthesis Assistant was used to analyze parameters related to responses to light and CO2. The level of statistical significance was P ≤ 0.05.

Results

Quantitative changes in plant growth parameters and plant density

Plant density, height, and fresh mass of L. chinensis were significantly affected by ABA and BR treatments (Figure 1). Plant density increased, compared to control, 49.6%, 60.7%, 60.7%, 85.9% and 76.9% at 2 × 10-4 mM BR, 0.01 mM ABA and 0.02 × 10-4 mM BR, 0.01 mM ABA and 0.2 × 10-4 mM BR, 0.01 mM ABA and 2 × 10-4 mM BR, 0.1 mM ABA and 2 × 10-4 mM BR treatments, respectively. Plant height increased 12.7%, 25.7%, 7.7%, and 9.2% , respectively at 0.01 mM ABA and 0.02 × 10-4 mM BR, 0.01 mM ABA and 0.2 × 10-4 mM BR, 0.01 mM ABA and 2 × 10-4 mM BR, 0.1 mM ABA and 2 × 10-4 mM BR treatments. However, plant height decreased 9.4% and 1.8% at ABA alone and BR alone treatments compared to the control. Plant biomass of the six respective treatments significantly increased 6.5%, 48.2%, 64.7%, 54.6%, 98.6%, 95.8% compared to the control. Various ABA and BR treatments showed significant differences (P ≤ 0.05) among treatments for L. chinensis leaf characters (Figure 2). For the leaves of single plant, results were in accordance with those for community plant biomass. The length and length/width ratio were significantly different (P ≤ 0.05) for 0.01 mM ABA and 2 × 10-4 mM BR, 0.1 mM ABA and 2 × 10-4 mM BR treatments, which increased length by 41.3% and 34.7%, respectively, and width by 28.3% and 28.2%,respectively, compared to control.
https://static-content.springer.com/image/art%3A10.1186%2F1999-3110-54-42/MediaObjects/40529_2011_Article_94_Fig1_HTML.jpg
Figure 1

Changes in the density, height and the FWof L. chinensis populations under ABA and BR treatments (Density: number of plants m -2 ; Height: cm; FW: fresh weight g m -2 ).

https://static-content.springer.com/image/art%3A10.1186%2F1999-3110-54-42/MediaObjects/40529_2011_Article_94_Fig2_HTML.jpg
Figure 2

Changes in the number, length, width and length/width of L. chinensis leaves under ABA and BR treatments (Leaf number: piece; Length: cm; Width: cm).

Diurnal patterns of leaf gas exchange

Diurnal patterns in PN were similar among treatments and exhibited bimodal curves, reflecting a significant drop at noon (Figure 3A, P ≤ 0.05). The daily average values of PN showed a upward trend. All treatments were significant higher than the control except the treatment of ABA alone. Notably, the 0.01 mM ABA and 2 × 10-4 mM BR treatment had the highest PN values among the treatments. There were no apparent differences in diurnal patterns in gs among the treatments. However, the average value of gs in ABA and BR treatments were significantly (P ≤ 0.05) higher than the control. Especially, 0.01 mM ABA and 2 × 10-4 mM BR treatments was significantly (P ≤ 0.05) higher than the control and other treatments (each increased on average by 74.0%, 45.0%, 29.2%, 52.2%, 18.6%, 29.6%). (Figure 3B). Diurnal patterns in Ci/ Ca did not differ significantly among treatments, presenting a general stable trend (Figure 3C). The daily average value of Ci/Ca also did not differ significantly among treatments. The diurnal patterns of E varied greatly among treatments, and at 12:00 h, the hormone treatment significantly (P ≤ 0.05) decreased the transpiration rate of L. chinensis leaves (Figure 3D). The daily average value of E showed a declining trend from ABA alone treatment to ABA and high BR treatment. High ABA and high BR treatment increased E but still lower than the control. Each of the treatments was on average lower by 2.1%, 9.6%, 14.0%, 15.9%, 24.4%, and 13.5% relative to the control. The pattern of daily WUE was similar to those of PN, showing a bimodal curve. At 14:00 h, the differences among treatments in WUE were the largest, and WUE of 0.01 mM ABA and 0.2 × 10-4 mM BR, and 0.01 mM ABA and 2 × 10-4 mM BR treatments were significantly (P ≤ 0.05) higher than the other treatments (Figure 3E). The daily mean WUE of L. chinensis increased due to treatments, except ABA alone. Treatment of 0.01 mM ABA and 2 × 10-4 mM BR showed the highest WUE, with 80.3%, 97.3%, 34.1%, 72.1%, 19.5%, and 25.5% increases over other treatments.
https://static-content.springer.com/image/art%3A10.1186%2F1999-3110-54-42/MediaObjects/40529_2011_Article_94_Fig3_HTML.jpg
Figure 3

Daily changes in photosynthetic parameter of L. chinensis under ABA and BR treatments. ( A ) net photosynthetic rate, PN, ( B ) stomatal conductance, gs, ( C ) transpiration rate, E, ( D ) ratio of stomatal and sub-stomatal CO2 concentrations, Ci/Ca, and ( E ) water use efficiency, WUE.

Photosynthetic response to light (A/Q)

Significant differences in photosynthetic parameters were observed among ABA and BR treatments with different concentrations (Table 2). The QE values of L. chinensis were increased in treatments compared to the control, 0.01 mM ABA and 2 × 10-4 mM BR, 0.1 mM ABA and 2 × 10-4 mM BR treatments were significantly higher than others. The Amax of 0.01 mM ABA was lower than the control; the other treatments were higher than the control plots, in particular, 0.01 mM ABA and 2 × 10-4 mM BR treatment increased Amax by 63.2%. However, LCP and LSE trended to decrease, especially for 0.01 mM ABA and 2 × 10-4 mM BR, 0.1 mM ABA and 2 × 10-4 mM BR treatments. The results showed that hormone treatments influenced photosynthetic responses to light.
Table 2

Photosynthetic parameters of L. chinensis in response to light under ABA and BR treatments

Treatment

Q E

A max [μmol m–2 s-1]

LCP

LSE

Control

0.02 ± 0.00d1

10.33 ± 0.93c

78.66 ±1.85a

502.80 ±10.77a

ABA

0.04 ± 0.00c

9.96 ± 0.85c

52.96 ± 1.94b

283.10 ± 9.56b

High BR

0.07 ± 0.00b

13.26 ± 0.67bc

52.28 ± 1.25b

255.20 ± 8.74b

ABA + low BR

0.06 ± 0.00b

13.88 ± 0.53bc

54.21 ± 1.68b

295.80 ± 10.65b

ABA + medium BR

0.07 ± 0.00b

13.64 ± 0.78bc

45.08 ± 1.34c

548.40 ± 11.28a

ABA + high BR

0.11 ± 0.00a

16.86 ± 0.91a

25.07 ± 1.25d

175.70 ± 10.34c

High ABA + high BR

0.11 ± 0.00a

14.14 ± 0.94b

24.58 ± 0.99d

157.00 ± 10.26c

(ABA: abscisic acid; BR: brassinolide; Q E : high energy state quenching; Amax:the maximum net photosynthesis; LCP: light compensation point; LSE: light saturation estimate. 1 : Different letters with a column indicate significate difference at P ≤ 0.05 ).

The responses of photosynthesis to CO2(A/Ci)

CO2 compensation point (CCP) were not affected by treatments, but there were significant differences in Asat, Resp, Vcmax, Jmax, VTPU, CE among treatments (Table 3). Asat and Resp showed no obvious change occurred between the ABA and the BR treatments versus the control, but the values under ABA and BR combined treatments were higher than that of the control, especially the 0.01 mM ABA and 2 × 10-4 mM BR treatment, increased Asat and Resp by 58.9% and 37.7%, respectively. Vcmax and CE showed similar patterns to A sat : with limited influence by ABA and BR treatments alone. However, the ABA and BR combined treatments affected Vcmax and CE significantly (P ≤ 0.05), especially for 0.01 mM ABA and 2 × 10-4 mM BR, and 0.1 mM ABA and 2 × 10-4 mM BR treatments. Jmax was higher in all treatments than the control, especially 0.01 mM ABA and 2 × 10-4 mM BR. VTPU was higher in all treatments than the control except 0.01 mM ABA and 0.2 × 10-4 mM BR; 0.1 mM ABA and 2 × 10-4 mM BR gave the largest increase among treaments.
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

[μmol m–2 s-1]

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; Asat: light-saturated rate of net photosynthesis; CCP: CO2 compensation point; Resp: respiration; Vcmax: maximum RUBP carboxylation rates; Jmax: the maximum electron transport; VTPU: 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.

Chlorophyll fluorescence

Fo was not significantly affected by treatments, but significant (P ≤ 0.05) differences in Fm and Fv were observed (Figure 4). Fm and Fv tended to increase from ABA alone to high ABA and high BR treatments, which were higher than the control. ABA alone, high BR, and 0.1 mM ABA and 2 × 10-4 mM BR were higher than the others in Fm and Fv. ABA caused a significant (P ≤ 0.05) decrease in Fv/Fm and BR caused a significant (P ≤ 0.05) increase in Fv/Fm compared to the control. When the two hormones were applied together, the ABA effect was counteracted by BR, and Fv/Fm showed higher values than when BR was applied alone. ABA alone, BR alone and high ABA and high BR treatments were significantly (P ≤ 0.05) higher (Figure 5) . Fv/Fo patterns strongly resembled that of Fm/Fo. Fm/Fo expresses the basal quantum yield of non-photochemical processes. From Figure 5, there were no notable differences between the control and treatments. All these results indicated that hormone treatments change the chlorophyll fluorescence of L. chinensis leaves and hence influence the photosynthesis.
https://static-content.springer.com/image/art%3A10.1186%2F1999-3110-54-42/MediaObjects/40529_2011_Article_94_Fig4_HTML.jpg
Figure 4

Changes in F o , F m and F v of L. chinensis under ABA and BR treaments (F o : initial fluorescence; F m : maximum fluorescence; F v : variable fluorescence).

https://static-content.springer.com/image/art%3A10.1186%2F1999-3110-54-42/MediaObjects/40529_2011_Article_94_Fig5_HTML.jpg
Figure 5

Changes in F v /F m ; F v /F o and F m /F o of L. chinensis under ABA and BR treaments (F v /F m : maximum quantum yield of PSII photochemistry; F v /F o : potential activityof PSII; F m /F o : electronic transfer efficiency of PSII) .

Discussion and conclusions

At present, global environment and crop production research lend special significance to improving plant photosynthesis, plant production and biomass through enhancing plant’s ability to resist saline-alkaline, drought and other environment stresses. Amongst others, plant growth regulators and related compounds have shown beneficial functions on the enhancement of plant growth performance and great potential to help realize those above mentioned goals.

Our experiment results indicated that the 0.01 mM ABA treatment inhibited leaf photosynthetic rate, stomatal conductance, and transpiration rate of mature L. chinensis to a certain extent, which are consistent with the results of former studies with inhibition of ABA on leaf gas exchange have been observed in several plant species Vardhini and Ramr (1998 Hou and Li 2001). We also observed that the application of 0.01 mM ABA treatment reduced the plant height and leaf quantity of the studied L. chinensis populations. However, it increased plant density, fresh mass, plant length and length width ratio of L. chinensis populations. Similar results have been reported by Saab et al. (1990) on the effects of ABA application on the growth of maize seedlings. Saab et al. (1990) found that ABA could promote the growth of maize seedling root, and inhibit stem and leaf growth under the water stress or water shortage condition. Moreover, we also found the special physiological effect of ABA treatment alone on other leaf photosynthetic parameters, such as an increase in the maximum RUBP carboxylation rate, leaf respiration rate, maximum electron transport, and maximum triose-phosphate utilization rate of L. chinensis leaves and a reduction in the light compensation point and light saturation estimates. The results of leaf chlorophyll fluorescence measurements suggest that ABA treatment enhanced anti-photoinhibition and the ability to resist harmful environments in L. chinensis. Overall, despite slightly reduction in plant height and leaf number per shoot, the gas exchange and chlorophyll fluorescence data indicate that the application of ABA alone enhanced leaf photosynthetic activities and CO2 assimilation rate.

BR is another important plant growth regulator, which has profound impacts of leaf photosynthesis and plant performance. The results of previous experiments suggest that BR improve leaf carbon assimilation rate through increasing the content of chlorophyll, which is the light harvesting machine of plant photosynthesis. Moreover, it has also showed that BR application could significantly alleviate the impacts of various abiotic stresses. For instance, BR treatment enhanced photosynthetic performance of cotton seedlings under NaCl stress Ding et al. (1995; Xiao et al. 2007; Chen et al. 2007; Shu et al. 2011). For cucumber seedlings, BR treatment has also been found to promote the occurrence of new roots and the formation of lateral roots Bao et al. (2004). Similar results were obtained in our experiment; BR treatment (2 × 10-4 mM) alone increased the photosynthetic carboxylation capacity and CO2 assimilation rate. Subsequently, BR treatment enhaned the plant density, height and biomass of the studied L. chinensis populations. As a saline alkali grassland rhizomatous plant, the occurrence of new and lateral roots is conducive for the growth as well as rhizome breeding of L. chinensis. The observed significant treatment effects of BR on L. chinensis may attribute to the stimulation of BR on the formation of new and lateral roots, which will not only directly enhance rhizome breeding and population density, but also indirectly improve plant water and nutrient uptake.

The effects of ABA or BR alone treatment on leaf gas exchange and plant performance have been conducted in various plants. However, the impacts of ABA and BR mixture on plant growth have been rarely tested, especially in perennial grasses. We studied the combined impacts of various ABA and BR mixtures on the leaf carboxylation capacity and growth performance of L. chinensis. The experimental results showed that ABA and BR treatments mixed in different proportions are evidently superior to treatments with ABA alone and BR alone on the enhancement of photosynthetic assimilation capacity and growth performance. The ABA and BR mixture treatments expressed not simply add up of the impacts of ABA and BR treatment alone, but showed compensatory effects between ABA and BR. This phenomenon is especially significant for the mixture of 0.01 mM ABA and 2 × 10-4 mM BR, which evidently increased PN, gs and WUE, as well as Amax, Asat,R esp, Vcmax, Jmax, VTpu, CE and quantum efficiency of PSII, and reduced the LCP and LSE. As a result of enhancement in photosynthetic capacity and CO2 assimilation rate, plant density, height and biomass were significantly increased in L. chinensis. Despite unclear in the underlying physiological mechanisms of the impacts of ABA and BR treatments on leaf photosynthetic capacity, the observed obvious effects of ABA and BR mixture on plant performance may attribute, to some extent, the compensatory impacts of ABA and BR treatment. For instance, BR application could improve root system and nutrient uptake, whereas ABA treatment enhanced photosynthetic capacities.

This experiment studied the impacts of ABA alone, BR alone and various mixture of ABA and BR on the performance of L. chinensis. Treatments of ABA alone or BR alone enhanced plant photosynthetic capacity and growth performance, however those effects were more significant when ABA and BR were implied in mixture. We proposed that there are compensatory effects between ABA and BR on regulating plant photosynthetic capacity and growth performance. Moreover, the experimental results provides evidence for enhancing the stress resistance of perennial plant populations and also builds a basis for recovering grasses growing under saline and alkaline conditions.

Abbreviations

ABA: 

Abscisic acid

Amax: 

The maximum net photosynthetic rate

Asat: 

Light-saturated rate of net photosynthesis

BR: 

Brassinolide

Ca: 

Atmospheric CO2 concentration

Ci: 

Intercellular CO2 concentration

CCP: 

CO2 compensation point

CE: 

Carboxylation efficiency calculated from CO2 response curve

E: 

Transpiration rate

Fo: 

Initial fluorescence

Fm: 

Maximum fluorescence

Fv: 

Variable fluorescence

gs: 

Stomatal conductance

Jmax: 

The maximum electron transport rate

LCP: 

Light compensation point

LSE: 

Light saturation estimate

PN: 

Net photosynthetic rate

QA: 

Primary electron acceptor

QE: 

High energy state quenching

Resp: 

Respiration

Vcmax: 

Maximum RUBP carboxylation rate

VTPU: 

Maximum rate of triose- phosphate utilization

WUE: 

Water use efficiency.

Declarations

Acknowledgements

This research was supported by the National Natural Science Foundation of China (No. 31270366, 30870238, 31270445), Natural Science Foundation of Jilin Province (No. 20100577) and Program for New Century Excellent Talents in University (NCET-12-0814).

Authors’ Affiliations

(1)
Key Laboratory for Vegetation Ecology, Ministry of Education, Institute of Grassland Science, Northeast Normal University
(2)
School of Life Sciences, Changchun Normal University

References

  1. Bajguz A, Hazat S: Effects of brassinosteroids on the plant responses to environmental stress. Plant Physiol Biochem 2009, 47: 1–8. 10.1016/j.plaphy.2008.10.002View ArticlePubMedGoogle Scholar
  2. Bao F, Shen J, Brady SR, Muday GK, Asami T, Yang Z: Brassinosteroids interact with auxin to promote lateral root development in Arabidopsis . Plant Physiol 2004, 134: 1624–1631. 10.1104/pp.103.036897PubMed CentralView ArticlePubMedGoogle Scholar
  3. Chen JH, Mao D, Ma ZY: Physiological Characteristics of Leaves of Bamboo Phyllostachvs pubescens. J Cent S Forest Univ 2006, 6: 77–81.Google Scholar
  4. Chen LX, Li YH, Zheng FE: Effect of brassinosteroids on soybean resistance to phytophthora sojae. Soybean Sci 2007, 5: 713–727.Google Scholar
  5. Ding JX, Ma GR, Huang SQ, Zhao YM: Studies on physiological effects of epiBR on cucumber ( Cucumis sativus L). J Zhejiang Agric Univ 1995, 6: 615–621.Google Scholar
  6. Dordas CA, Sioulas C: Safflower yield, chlorophyll content, photosynthesis and water use efficiency response to nitrogen fertilization under rain fed conditions. Ind Crop Prod 2007, 1: 75–85.Google Scholar
  7. Field CB, Ball JT, Berry JA (Eds): Plant Physiological Ecology. New York: Chapman and Hall Press; 1989:209–253.View ArticleGoogle Scholar
  8. Franks PJ, Farquhar GD: The Effect of Exogenous Abscisic Acid on Stomatal Development, Stomatal Mechanics, and Leaf Gas Exchange in Tradescantia virginiana . Plant Physiol 2001, 2: 935–942.View ArticleGoogle Scholar
  9. Hou LP, Li ML: Progress of Studies on the Plant Growth Promoting Mechanism of Brassinolide(BR). Chinese Bull Bot 2001, 5: 560–566.Google Scholar
  10. Jia HS, Lu CM: Effects of abscisic acid on photo inhibition in maize plants. Plant Sci 2003, 165: 1403–1410. 10.1016/j.plantsci.2003.08.004View ArticleGoogle Scholar
  11. Khripach V, Zhabinskii V, Groot AD: Twenty years of Brassinosteroids: Steroidal plant hormones waeant better crops for the XXI century. Ann Bot 2000, 86: 441–447. 10.1006/anbo.2000.1227View ArticleGoogle Scholar
  12. Krouk G, Ruffel S, Rodrigo A, Gutie’rrez RA: A framework integrating plant growth with hormones and nutrients. Trends Plant Sci 2011, 4: 178–182.View ArticleGoogle Scholar
  13. Li JD, Zheng HY (Eds): The Control of Alkalinized-Salinized Grasslands in the Songnen Plain and Their Mechanisms. Beijing: Science Press; 1997:5–102.Google Scholar
  14. Li X, Zhang L, He X: Effects of abscisic acid on photosynthetic characteristics and antioxidant enzyme activities of wheat seedlings. Chinese J App Ecol 2006, 5: 822–826.Google Scholar
  15. Liu DB, Wei JY, Li SP, Cui BM, Peng M: Effects of Brassinolid on chilling-resistance in banana Seedlings. Bull Bot Res 2008, 2: 195–221.Google Scholar
  16. Long SP, Bernacchi CJ: Gas exchange measurements, what can they tell us about the underlying limitations to photosynthesis? Procedures and sources of error. J Exp Bot 2003, 54: 2393–2401. 10.1093/jxb/erg262View ArticlePubMedGoogle Scholar
  17. Mawson BT, Colman B, Cummin WR: Abscisic Acid and Photosynthesis in Isolated Leaf Mesophyll Cell. Plant Physiol 1981, 2: 233–236.View ArticleGoogle Scholar
  18. Mclaren JS, Smith H: Effect of abscisic acid on photosynthetic products of Lemna minor . Phytochemistry 1977, 2: 219–221.View ArticleGoogle Scholar
  19. Olsson T, Leverenz JW: Non-uniform stomatal closure and the apparent convexity of the photosynthetic photon flux density response curve. Plant Cell Environ 1994, 17: 701–710. 10.1111/j.1365-3040.1994.tb00162.xView ArticleGoogle Scholar
  20. Peleg Z, Blumwald E: Hormone balance and abiotic stress tolerance in crop plants. Curr Opin Plant Biol 2011, 14: 290–295. 10.1016/j.pbi.2011.02.001View ArticlePubMedGoogle Scholar
  21. Prioul JL, Chartier P: Partitioning of transfer and carboxylation components of intracellular resistance to photosynthetic CO 2 fixation: A critical analysis of the methods used. Ann Bot 1997, 41: 789–800.Google Scholar
  22. Saab IN, Sharp RE, Pritchard J, Voetberg GS: Increased endogenous abscisic acid maintains primary root growth and inhibits shoot growth of maize seedlings at low water potentials. Plant Physiol 1990, 93: 1329–1336. 10.1104/pp.93.4.1329PubMed CentralView ArticlePubMedGoogle Scholar
  23. Šafránková I, Hejnák V, Stuchlíková K: The effect of abscisic acid on rate of photosynthesis and transpiration in six barley genotypes under water stress. Cereal Res Commun 2007, 2: 1013–1016.View ArticleGoogle Scholar
  24. Sankhla N, Huber W: Effect of Abscisic Acid on the Activities of Photosynthetic Enzymes and 14 CO 2 Fixation Products in Leaves of Pennisetum typhoides Seedlings. Physiol Plant 1974, 4: 291–294.View ArticleGoogle Scholar
  25. Shi LX, Guo JX: Changes in photosynthetic and growth characteristics of Leymus chinensis community along the retrogression on the Songnen grassland in northeastern China. Photosynthetica 2006, 4: 542–547.View ArticleGoogle Scholar
  26. Shu HM, Guo SQ, Shen XL, Ni WC: Cotton physiology affected by brassinosteroid under NaCl stress. Jiangsu J of Agr Sci 2011, 6: 1198–1202.Google Scholar
  27. Vardhini BV, Ramr SS: Effect of brassinosteroids on growth, metabolite content and yield of Arachishy pogaea . Phytochemistry 1998, 6: 927–930.View ArticleGoogle Scholar
  28. Wang P, Zhou DW: Research on the Utilization Modes of Hordeum Brevisulatum and Leymus Chinensis Based on the Comparison of Photosynthesis and Transpiration. Grassland of China 2004, 26: 3.Google Scholar
  29. Wu CT: The Interaction and Relationship between Nitric Oxide and Phytohormone. Genom App Biol 2010, 6: 1169–1176.Google Scholar
  30. Wu YY, Li PP, Zhao YG, Wang JZ, Wu XG: Study on photosynthetic characteristics of Orychophragmus violaceus related to shade-tolerance. Sci Hortic 2007, 113: 173–176. 10.1016/j.scienta.2007.02.004View ArticleGoogle Scholar
  31. Xiao L, Pang RH, Cai RX, Yu P, Huang XH, Wang L: Physiological Effect and Yield Increase Action after Spraying BR in Rice Early Blooming Stage. J Anhui Agri Sci 2007, 11: 3317–3330.Google Scholar
  32. Zhou BY, Guo ZF, Lin L: Effects of Abscisic Acid Application on Photosynthesis and Photochemistry of Stylosanthes guianensis under Chilling Stress. Plant Growth Regul 2006, 3: 195–199.Google Scholar

Copyright

© Hu et al.; licensee Springer. 2013

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.