Introduction
Buckwheat belongs to the genus Fagopyrum Mill., which is widely distributed in the world and
mainly cultivated in Russia, China, Ukraine, France, Kazakhstan, Poland, and
Japan. Common buckwheat (Fagopyrum
esculentum Moench) and Tartary buckwheat (Fagopyrum tataricum Gaertn) are the two main cultivated species of
buckwheat (Wijngaard and Arendt 2006; Chen 2018). Owing to its high flavonoids
and D-chiral inositol content, Tartary buckwheat can lower blood sugar, blood
pressure, and blood lipid, anti-tumor, and improve intellectual functions (Giménez-Bastida
and Zieliński 2015). Tartary buckwheat is a food crop with great health
benefits, but at present, its yield is low at approximately1500–2400 kg·ha-1
(Song et al. 2014a). Therefore,
achieving a high yield of Tartary buckwheat is crucial to promoting the
development of the buckwheat industry (Huang et al. 2019).
Leaves are
important source organs for crops, while seeds are important sink organs. The
ability of light capturing of leaves, product distribution and yield formation
are closely related during grain filling period (Kato and Takeda 1996). The
accumulation of starch in the grain is widely believed to be the result of
plant photosynthesis, and net photosynthetic rate is the most direct effect on
the light energy utilization of the crops. Photosynthetic assimilates are transferred from the source (leaf and stem) to the seed
in the form of sucrose, and starch is formed by a series of enzymatic reactions
(Peng et al. 1999). In this process,
key enzymes of the sucrose-starch metabolism pathway, such as adenosine
diphosphate glucose
pyrophosphate (AGPase), soluble starch polymerase (SSS), and starch branching
enzyme (SBE), play an important role in grains (Kato et al. 2007).
Nitrogen (N), a
significant element of plant growth and development, plays an important role in
crop growth and yield formation (Xu et al.
2013). Lu et al. (2007) found that
the application of nitrogen can affect the grain filling characteristics of
crops and its suitable application can increase the yield. Xu et al. (2015) found that the suitable application N fertilizer can
increase the weight of inferior spikelet and final yield of rice and other
crops. Zhang et al. (2020a) found
that the poor grain filling and low grain weight of inferior spikelet limit the yield of Tartary buckwheat. Wang et al. (2019) reported that suitable N fertilizer could
promote the growth and increase the yield of
Tartary buckwheat. However,
the mechanism of inferior spikelet formation and the relationship between the N
fertilizer applications is lacking. We predict that N fertilizer application affects
the formation of superior and
inferior spikelet of Tartary buckwheat, thus affecting the final yield. Thus, this study investigated the effects of different N fertilizer applications on the grain filling
characteristics of superior and inferior spikelet and the yield formation of
Tartary buckwheat by using “cv Jinqiao 2” (JQ2) as the experimental material.
The results can provide a theoretical basis for cultivating high-yield Tartary
buckwheat.
Materials and Methods
Plant materials and growth
High yield Tartary
buckwheat cultivated varieties JQ2 was provided by the Buckwheat Industry Technical
Research Center of Guizhou Normal University, China. The experiment was
conducted on March 7, 2018 and March 2, 2019 in the cement pools at Huangnitang’s
Cultivation Experiment Station of Guizhou Normal University, China (Bijie City,
Guizhou Province, China, 922 m, 27°05′N and 105°71′E). The soil
used was yellow loam with 36.52 g·kg−1
organic matter, 48.25 g·kg−1 available nitrogen, 312.50 mg·kg−1
available phosphorus and 132.39 mg·kg−1 available potassium
(determined by using a soil nutrient rapid analyzer, OK-Q3, China). Soil pH was
5.76. Monthly average temperature from March to June was 19.8°C and day length
of 124.6 h in 2018, and 18.4°C and 113.0 h in 2019.
Tartary buckwheat was cultivated in cement pools with an area of 2 m × 10
m × 0.3 m. Different nitrogen fertilizers were applied at 0, 45, 135 and 225 kg·ha−1 (urea) and
labeled as CK (0N), LN (Low N, N1), MN (Medium N, N2), and HN (High N, N3),
respectively. The optimum application rates of phosphorus and potassium using
calcium superphosphate and potassium chloride fertilizers were 70 and 5.0 kg·ha−1, respectively
(Song et al. 2014b). Three kinds of fertilizers were mixed well and applied as base fertilizer at one-time, and no
fertilizer was applied throughout the growth period. The spacing for each row spanned 33 cm, seeding amount was 2.625 g·m-2
and approximately 45–50 reserved plants were available for each m2.
The Tartary buckwheat seeds were harvested when no shattering and 70% of seeds
turned brown yellow (Zhang and Lin 2007) on June 10, 2018 and June 4, 2019. All
treatments were repeated three times, and normal agricultural practices were
implemented.
Sample preparation
The plants with uniform growth and no diseases and insect pests were
selected from the pools of each nitrogen fertilizer treatment after flowering.
At the beginning of the flowering period, approximately 1000–1500 flowers
bloomed on the same day when Tartary buckwheat plants were marked in each pool
and the marked flowers were sampled every five days from flowering (5 May 2018
and 1 May 2019) to maturation, six times samples were collected. These were
used to determine the grain filling characteristics of Tartary buckwheat. The
superior and inferior spikelet of the Tartary buckwheat were divided according to
the results of an earlier study (Wang et
al. 2016): the superior spikelet (SS) was the grain with one to three nodes
at the top of the main stem of Tartary buckwheat, and the inferior spikelet
(IS) was the grain on the secondary branch at the base of Tartary buckwheat
(Funatsuki et al. 2000).
After shelling, half-sampled grains at every
period and every treatment were frozen in liquid nitrogen for 1 min and
then stored at −80°C for starch synthase enzymatic measurement. The other
half of the grain samples was dried at 60°C to a constant weight to analyze
grain filling characteristics and starch content.
Five days after anthesis, the leaves where
the superior and inferior spikelet was located were collected every five days
to determine the activity of antioxidant enzymes and the content of
malondialdehyde (MDA) in Tartary buckwheat, respectively.
Determinations
Grain filling
simulation: Dried grains were weighed to calculate the average dry weight of 100 grains.
In accordance with Zhu et al. (1988),
Richards’s equation was used to describe the grain-filling process.
W =A/(1 + Be−Kt)1/N
Divided
grain-filling stage: With reference to Yang et al.
(2013), the contribution rates of the grain-filling period that includes the
prophase of filling stage (RGC1), the middle of filling stage (RGC2), and the
anaphase of filling stage (RGC3) for grain weight were calculated as described.
RGC1 = W1/A×100%
RGC2 = (W2－W1)/A×100%
RGC3 = (W3－W2)/A×100%
Starch synthase
enzyme activity: The activities of glucose pyrophosphorylase (AGPase) and soluble starch
synthase (SSS) in the grains were determined using the method of Yang et al. (2003). With reference to
Nakamura and Yuki (1992), the activities of starch branching enzyme (SBE) were
determined.
Photosynthetic characteristics: The net photosynthetic rate,
stomatal conductance, and transpiration rate were determined using an American
LI-COR-6400 portable photosynthetic apparatus (Li-Cor 6400, Li-Cor, Lincoln,
NE, USA). The assay time was from 10:00 a.m. to 11:00 a.m., and 10 leaves
(where the superior and inferior spikelet located) were measured for each
treatment.
Antioxidant enzyme
activity and MDA content: The SOD activity was determined using the NBT method, the POD and CAT
activities were measured using an ultraviolet spectrophotometer, and the MDA
was determined through thiobarbituric acid method (Zhang 1990).
Agronomic characters
and yield: Plant height, main stem branch number, main stem node number, grain
number per plant, grain weight per plant, and 1000 grain weight of each
nitrogen fertilizer treatment were determined following Zhang and Lin (2007).
The yield was determined at maturity and converted per ha yield. The harvest
index= grain yield/total biomass ×100.
Statistical analysis
Microsoft Excel 2003 and S.P.S.S. 22.0 were used for processing, and
one-way analysis of variance was performed. Sigma Plot 14.0 was used for
drawing.
Results
Simulation of
grain-filling process
The 100-grain weight of grain increased at first and then
decreased with the increase of nitrogen application (Fig. 1). The maximum grain
weight was under MN treatment. The 100-grain weight increased rapidly at the early filling stage, and
the extent of seed growth decreased 25 days after anthesis. The 100-grain
weight of the superior spikelet was obviously higher than inferior spikelet.
The 100-grain weight of each treatment was lower in 2019 than in 2018. The
trends in 2019 and 2018 were similar.
The determination coefficient R2 of each curve equation ranged from 0.99 to 1.00 (Table
1). MN treatment had the highest
final grain weight at harvest (A)
value among the different N fertilizer treatments, except for when LN treatment was
the highest in 2019. Moreover, except for the inferior spikelet applied in LN
in 2019, the A value of the superior
spikelet was higher than the inferior spikelet. The shape parameter value (N) was less than 1,
except for the inferior spikelet applied with HN in 2018.The N value of the inferior spikelet was
higher than superior spikelet. Under MN treatment, the time to reach the
maximum filling rate (Tmax.G)
was the shortest, but the maximum grain filling rate (Gmax) and average grain filling rate (Gmean) were the highest. The
filling initiation potential (R0),
Gmax, and Gmean of the superior spikelet
were higher than inferior spikelet. There were differences in grain filling
active growth period (D) among
different N fertilizer
treatments. The superior spikelet was the largest in 0N treatment, and the
inferior spikelet was the largest in the LN treatment. The active growth period
for grain filling of the inferior spikelet was generally higher than superior
spikelet. The results in 2019 and 2018 were similar.
Grain-filling
stages of tartary buckwheat
In 2018, the
duration of early filling stage of the superior spikelet was the shortest in MN
treatment, and the inferior spikelet in LN treatment (Table 2). The average
filling rate was the highest in MN treatment. The contribution rate of duration
to the grain weight of the early filling stage was the highest in HN treatment.
Compared with the superior spikelet, duration days of the early filling stage
of the inferior spikelet were longer, the average filling rate was smaller, and
the contribution rate of duration days to grain weight was larger.
Duration days in the middle and late filling stage of the superior
spikelet was the shortest in LN treatment, whereas was the longest of the
superior spikelet in MN treatment and in HN treatment during middle filling
stage. The average filling rate was the highest in MN treatment, and the
contribution rate of the middle and late filling stage to grain weight was the
largest in LN treatment. Compared with the superior spikelet, duration days of
the inferior spikelet at the middle and late filling stage were longer, the
average filling rate was smaller, and the contribution rate of duration days of
the middle and late filling stage to grain weight was smaller.
The contribution rate to grain weight in the middle filling stage was
the largest, followed by the later filling stage, and then the early filling
stage. The results in 2019 and 2018 were similar.
Starch accumulation
and starch synthase enzyme activity
The starch content
increased at first and then decreased with the increase in N application rate and finally reached the maximum at MN
treatment (Fig. 2). The starch content of the superior spikelet was higher than
the inferior spikelet. The AGPase and SSS activity of grains was generally the
largest in MN treatment. With the increase in growth stage, the AGPase and SSS
activity increased initially and then decreased. The AGPase and SSS activity of
the superior spikelet reached the highest 15 days after anthesis, whereas the
AGPase and SSS activity of the inferior spikelet reached the maximum 20 days
after anthesis. In the early filling stage (5–15 days), the AGPase and SSS
activity of the superior spikelet was higher, whereas of the inferior spikelet
was higher in the middle and late filling stages (20–30 days). The SBE activity
increased continuously with the increase in N
application rate, and the HN treatment was the largest. The SBE activity of
grains increased at first and then decreased with the advance of growth period,
and finally reached the maximum 10 days after anthesis. The SBE activity of the
superior spikelet was higher than the inferior spikelet. The results in 2019
and 2018 were similar.
Photosynthetic
characteristics
Table 1: Parameters of the Richards equation for evaluating the
grain-filling process of Tartary buckwheat
|
Year |
Grain position |
Treatment kg·ha−1 |
A |
B |
K |
N |
R2 |
R0 |
Tmax. G/d |
Gmax/ (g/100·d) |
Gmean(g/100) |
D/d |
|
2018 |
SS |
0
(0N) |
2.55 |
0.02 |
0.13 |
0.01 |
1.00 |
23.30 |
9.47 |
0.12 |
0.08 |
31.19 |
|
45
(LN) |
2.95 |
0.01 |
0.15 |
0.00 |
0.99 |
51.51 |
7.66 |
0.16 |
0.11 |
27.61 |
||
|
135
(MN) |
3.28 |
0.02 |
0.14 |
0.01 |
1.00 |
24.19 |
7.55 |
0.17 |
0.11 |
28.57 |
||
|
225
(HN) |
2.93 |
0.02 |
0.14 |
0.01 |
1.00 |
19.99 |
7.90 |
0.15 |
0.10 |
28.69 |
||
|
IS |
0
(0N) |
2.45 |
1.38 |
0.14 |
0.26 |
0.99 |
0.54 |
12.06 |
0.11 |
0.08 |
32.60 |
|
|
45
(LN) |
2.90 |
0.89 |
0.12 |
0.22 |
0.99 |
0.55 |
12.04 |
0.11 |
0.08 |
37.70 |
||
|
135
(MN) |
3.02 |
1.56 |
0.14 |
0.33 |
0.99 |
0.42 |
11.23 |
0.13 |
0.09 |
33.53 |
||
|
225
(HN) |
2.43 |
20.54 |
0.20 |
1.20 |
0.99 |
0.17 |
13.98 |
0.12 |
0.08 |
31.44 |
||
|
2019 |
SS |
0
(0N) |
2.54 |
0.01 |
0.13 |
0.00 |
1.00 |
44.20 |
9.44 |
0.12 |
0.08 |
30.79 |
|
45
(LN) |
2.76 |
0.02 |
0.15 |
0.00 |
1.00 |
33.86 |
8.86 |
0.15 |
0.10 |
26.67 |
||
|
135
(MN) |
2.99 |
0.51 |
0.16 |
0.13 |
1.00 |
1.25 |
8.81 |
0.16 |
0.11 |
26.90 |
||
|
225
(HN) |
2.63 |
0.02 |
0.14 |
0.01 |
0.99 |
24.37 |
8.23 |
0.14 |
0.09 |
28.56 |
||
|
IS |
0
(0N) |
2.12 |
11.92 |
0.20 |
0.69 |
1.00 |
0.29 |
14.46 |
0.12 |
0.08 |
27.22 |
|
|
45
(LN) |
2.81 |
2.00 |
0.13 |
0.31 |
1.00 |
0.41 |
14.68 |
0.11 |
0.08 |
36.21 |
||
|
135
(MN) |
2.71 |
9.18 |
0.20 |
0.72 |
0.99 |
0.27 |
13.03 |
0.14 |
0.10 |
27.83 |
||
|
225
(HN) |
2.29 |
10.27 |
0.19 |
0.72 |
1.00 |
0.26 |
14.23 |
0.12 |
0.08 |
29.18 |
Fig. 1: The hundred-grain weight of Tartary buckwheat (g/100 grains FW)
Note: N0-SS mean superior
spikelet with no nitrogen (0 kg·ha-1), N0-IS mean inferior spikelet with no nitrogen
(0 kg·ha-1), N1-SS mean superior spikelet with low nitrogen
(45 kg·ha-1), N1-IS mean inferior spikelet with low nitrogen
(45 kg·ha-1), N2-SS mean superior spikelet with middle
nitrogen (135 kg·ha-1), N2-IS mean inferior spikelet with middle
nitrogen (135 kg·ha-1), N3-SS mean superior spikelet with high nitrogen
(225 kg·ha-1), N3-IS mean inferior spikelet with high nitrogen
(225 kg·ha-1)
The net
photosynthetic rate and the stomatal conductivity increased at first and then
decreased, whereas the transpiration rate decreased at first and then increased
and then decreased toward the growth period (Fig. 3). The net photosynthetic
rate, the stomatal conductivity, and the transpiration rate of different N fertilizer treatments were different, and generally the
largest in MN treatment. The net photosynthetic rate, the stomatal
conductivity, and the transpiration rate of the superior spikelet were higher
than inferior spikelet. The trend in 2019 was similar to 2018.
Antioxidant enzyme
activity and MDA content
The activities of
SOD, POD, and CAT in leaves increased initially and then decreased with the
advance of the growth period (Fig. 4). The activities of SOD, POD, and CAT were
the strongest in MN treatment. Their activities in the superior spikelet were
generally higher than in the inferior spikelet. MDA content in the leaves
showed a continuous increasing trend toward the growth period. MDA content in
MN treatment was the lowest among different N fertilizer
treatments. MDA content of the inferior spikelet was generally higher than
superior spikelet. The trend in 2019 was similar to 2018.
Agronomic traits
and yield
The plant height,
the number of main stem nodes, main stem branches, grain number per plant,
grain weight per plant, 1000-grain weight, and yield in MN treatment were
higher than other three N fertilizer
treatments (Table 3). The 1000-grain weight of the superior spikelet was
significantly higher than inferior spikelet. The harvest index in MN and HN
treatment were significantly higher than other two N fertilizer treatments, and there was no significant
difference in harvest index between MN and HM treatments. The trend in 2019 was
similar to 2018.
Discussion
The Richards
equation (Richards 1959) growth curve was used to fit the filling process of
Tartary buckwheat, the determination
coefficient R2 of each curve equation ranged from 0.99 to
1.00, which indicated that it is feasible to fit the filling process of Tartary
buckwheat with Richards’s equation. The grain weight of crops mainly depends on the grain filling rate, and
a high Gmean is prerequisite for obtaining a high grain weight (Wang et al. 2017). Nitrogen application
significantly affects the grain filling of the crop. Wang et al. (2013) found that in a certain range, the application of N fertilizer can increase Gmax, delay the start time of grain filling, advance Tmax.G, and increase the
final grain weight and yield. In this
study, MN treatment could increase Gmax and Gmean of the
superior and inferior spikelet and reduce Tmax.G,
which was consistent with Wang et al.
(2013) that excessive or
insufficient N fertilizer
application would both reduce the filling rate and thus affect grain weight and
final yield (Wang et al. 2019).
Table 2: The divided
grain-filling stage of Tartary buckwheat
|
Year |
Grain position |
Treatment kg·ha−1 |
Early filling stage |
Middle filling stage |
Later filling stage |
||||||
|
duration/d |
average rate (g/100·d) |
contribution/% |
duration/d |
average rate (g/100·d) |
contribution/% |
duration/d |
average rate (g/100·d) |
contribution/% |
|||
|
2018 |
SS |
0 (0N) |
1.96 |
0.10 |
7.39 |
16.97 |
0.10 |
60.96 |
45.24 |
0.03 |
30.66 |
|
45 (LN) |
1.02 |
0.21 |
7.34 |
14.30 |
0.14 |
60.96 |
39.36 |
0.04 |
30.70 |
||
|
135 (MN) |
0.67 |
0.36 |
7.39 |
14.42 |
0.15 |
60.96 |
40.31 |
0.04 |
30.65 |
||
|
225 (HN) |
1.00 |
0.22 |
7.41 |
14.81 |
0.13 |
60.96 |
40.79 |
0.03 |
30.63 |
||
|
IS |
0 (0N) |
4.34 |
0.06 |
11.39 |
19.78 |
0.10 |
60.61 |
45.24 |
0.03 |
27.01 |
|
|
45 (LN) |
3.08 |
0.10 |
10.72 |
21.00 |
0.10 |
60.71 |
51.18 |
0.03 |
27.57 |
||
|
135 (MN) |
3.33 |
0.11 |
12.41 |
19.12 |
0.12 |
60.42 |
44.35 |
0.03 |
26.17 |
||
|
225 (HN) |
7.23 |
0.08 |
23.29 |
20.73 |
0.10 |
56.84 |
36.57 |
0.03 |
18.87 |
||
|
2019 |
SS |
0 (0N) |
2.03 |
0.09 |
7.34 |
16.84 |
0.10 |
60.96 |
44.79 |
0.03 |
30.70 |
|
45 (LN) |
2.44 |
0.08 |
7.37 |
15.28 |
0.13 |
60.96 |
39.47 |
0.03 |
30.67 |
||
|
135 (MN) |
2.38 |
0.12 |
9.34 |
15.24 |
0.14 |
60.87 |
37.90 |
0.04 |
28.79 |
||
|
225 (HN) |
1.36 |
0.14 |
7.39 |
15.09 |
0.12 |
60.96 |
40.97 |
0.03 |
30.65 |
||
|
IS |
0 (0N) |
8.27 |
0.04 |
17.35 |
20.65 |
0.10 |
59.10 |
37.75 |
0.03 |
22.55 |
|
|
45 (LN) |
6.14 |
0.06 |
12.13 |
23.22 |
0.10 |
60.47 |
50.75 |
0.03 |
26.40 |
||
|
135 (MN) |
6.73 |
0.07 |
17.77 |
19.33 |
0.13 |
58.97 |
36.55 |
0.04 |
22.27 |
||
|
225 (HN) |
7.63 |
0.05 |
17.80 |
20.84 |
0.10 |
58.96 |
38.87 |
0.03 |
22.25 |
||
Fig. 2: The starch
accumulation and starch synthase activity of Tartary buckwheat at different
days after anthesis
Jiang et al. (2003) found
that the activity of the key enzymes of starch synthesis in wheat increased
with the increase of N application. Ma et al. (2007) found that the AGPase,
SSS, SBE and GBSS activities of wheat increased
at first and then decreased with the increase of N application. Similar results were obtained in the present study. Combined with the results that net photosynthetic rate,
stomatal conductance, and transpiration rate of MN treatment were the highest,
it was considered that the suitable N fertilizer
treatment enhanced the utilization efficiency of the light energy and increased
the “source,” that is, the grain filling material was increased, so as, to
promote the filling of the superior and inferior spikelet. Zhang et al. (2020b) found that suitable N fertilizer application had the highest Gmax and Gmean, and the activity of the starch synthase is beneficial to increase in final grain weight and yield as evident from present
study results.
Table 3: Agronomic traits and yield of Tartary buckwheat
|
Year |
Treatment kg·ha−1 |
Plant height (cm) |
Number of main stem
nodes |
Number of branches of
main stem |
Grain number per plant |
Grain weight per plant
(g) |
1000-grain weight (g) |
Yield (kg·ha-1) |
Harvest index (%) |
|
|
SS |
IS |
|||||||||
|
2018 |
0 (0N) |
120.87c |
11.33b |
8.00c |
492.33d |
11.59d |
22.77d |
20.68d |
943.61d |
36.82c |
|
45 (LN) |
124.47b |
10.33c |
8.67b |
520.33b |
13.19b |
27.95b |
25.76b |
1409.97b |
41.39b |
|
|
135 (MN) |
138.33a |
15.33a |
9.67a |
608.00a |
14.86a |
34.17a |
32.22a |
1680.14 a |
4794a |
|
|
225 (HN) |
126.60b |
11.67b |
7.33d |
503.67c |
12.12c |
25.36c |
23.45c |
1218.88c |
4787a |
|
|
2019 |
0 (0N) |
54.00c |
10.33c |
3.67c |
465.00c |
9.68d |
22.09d |
20.16d |
908.92d |
3340c |
|
45 (LN) |
63.00b |
10.00c |
5.33b |
518.00b |
11.44b |
27.07b |
25.08b |
1286.75b |
36.44b |
|
|
135 (MN) |
72.17a |
14.33a |
6.67a |
538.67a |
13.29a |
30.36a |
28.39a |
1480.87a |
42.39a |
|
|
225 (HN) |
61.63b |
12.33b |
3.67c |
397.67d |
10.35c |
25.01c |
23.15c |
1154.01c |
4146a |
|
Fig. 3: Photosynthetic
characteristics of Tartary
buckwheat at different days after anthesis
Yang et al. (2001) found that
the activity of the key enzymes of starch synthesis in rice in the superior
spikelet during the early stage of the filling were higher than the inferior
spikelet, whereas those at the later period of the filling in the superior
spikelet were lower than in the inferior spikelet. Zhang et al. (2020a) found that the inferior spikelet had low Gmax, Gmean, photosynthetic rate, stomatal
conductance, and transpiration rate in the early filling stage. Similar results
were obtained in the present study, indicating
that the low light energy utilization and low starch synthase activity
at the early stage of the filling are highly attributed to the small grain
filling rate and light grain weight (Fu et
al. 2012).
Ye et al. (2011) found that the activities of SOD, POD, and CAT in leaves of maize increased
initially and then decreased with the
increase of N application, whereas
the content of MDA was the lowest under suitable
N fertilizer application,
increasing or decreasing the application of N fertilizer would increase the
content of MDA. Similar results were obtained in the present study, indicating that applying the proper amount of N fertilizer can delay the early senescence of Tartary
buckwheat, thus prolonging the grain filling time, and finally increasing the
grain weight and yield (Thomas and Smart, 1993; Zhang et al. 1998). This outcome is consistent with the results of
previous studies (Wu et al. 2019).
Conclusion
Low
light energy utilization and resource assimilation efficiency are important
physiological factors for formation of inferior spikelet. Suitable N fertilizer application (135 kg·ha−1, MN) have the largest harvest index,
increasing the photosynthetic efficiency and resource assimilation efficiency,
promote the filling of the superior and inferior spikelet, and increase the
grain weight and final yield of buckwheat.
Acknowledgments
We
acknowledge the support of Joint Project of Natural Science Foundation of China
and Guizhou Provincial Government Karst Science Research Center (U1812401), the
Science and Technology Support Plan of Guizhou province, China
(QianKeHeZhiCheng [2019]2297), the Major Research Projects of Innovation Groups
of Guizhou province, China (QianJiaoHe KY Zi [2018]015), and the science and
technology projects of Guiyang, China (ZhukeHetong
[2019]11-6).
Fig. 4: Antioxidant enzyme activity and
MDA content of Tartary buckwheat
Author Contributions
Y Zhang and KF Huang, devised the
study;Y Zhang, XH Wu, XY Huang, PY He and QF Chen, performed the experiments; Y
Zhang, analyzed the data; Yu Zhang and KF Huang, wrote the manuscript.
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