| 其他摘要 | The source-sink relationship determines crop yield. This has been widely
investigated in cereals such as wheat and rice, but fewer studies have been conducted in
root and tuber crops such as potato (Solanum tuberosum L.). As one of the major food
crops in the world, potato is a typical kind of tuber crops. Its harvest organ tuber is a
kind of modification of stems. It is a vegetative organ and not a reproductive organ like
seed in cereal crops. Thus, understanding the source-sink relationship in potato is very
important for improving potato potential yield and understanding the source-sink
relationships in tuber crops. Water and nitrogen are two key factors affected crop
production, and are also two main factors that can be regulated by farmers. There are
lots of studies about the regulatory mechanisms of water and nitrogen on source-sink
relationships in cereals, but in potato these studies are few. Therefore, using virus-free
plantlets of the Atlantic potato cultivar, a pot experiment was conducted to study the
influence of water and nitrogen on the tuber yield, source-sink relationship, carbon and
nitrogen metabolism relationship, water and nitrogen use efficiency in potato. The
results would help to determine the source-sink relationship in potato and understand
the regulatory mechanism of water and nitrogen on it. The main results were as follows.
1. The source-sink relationship in potato yield formation. By designing
different water and nitrogen levels, the changes of tuber yield, whole plant biomass,
harvest index, source capacity, sink capacity, water and nitrogen use efficiency in potato
during the tuber bulking stage were studied. The results showed that, plant source
capacities were small under all water and nitrogen levels at the end of the experiment,
but at this time, sink tuber still had a large potential capacity to take in assimilates. It
suggests that the source-supplied assimilates were not sufficient enough to meet the demands of sink growth. Thus, we concluded that, unlike cereals, potato yield is more
likely to be source-limited than sink-limited during the tuber bulking stage. Different
water and nitrogen levels affected tuber yield by influencing plant source capacity.
Well-watered (90% of field capacity) and sufficient nitrogen (0.2 g N/kg soil) conditions
increased yield mainly by enhancing the source capacity. In addition, among all
treatments, tuber yield and total biomass were the highest under the well-watered and
sufficient nitrogen conditions, but harvest index were not the highest under these
conditions. It also suggests that well-watered and sufficient nitrogen conditions
increased the amount of total biomass plant accumulated, but not increased the amount
of biomass partitioned to tubers (harvest index) to increase tuber yield, and then
increase water and nitrogen use efficiency. Therefore, these results suggest that plant
source capacity is the main limiting factor in potato production. Increasing net
photosynthetic rate, total leaf area and leaf life span to increase plant source capacity is
more crucial to improve potato potential yield.
2. The carbon-nitrogen metabolism coordination and source-sink relationship
in potato. The coordination of carbon and nitrogen metabolism determines crop yield.
By designing different water and nitrogen levels, the changes of carbon-nitrogen
metabolism coordination, namely carbon/nitrogen ratio in potato during the tuber
bulking stage were studied. The results showed that, carbon/nitrogen ratio in potato
leaves were negatively correlated to the chlorophyll content. Water stress increased the
carbon/nitrogen ratio, and sufficient nitrogen level maintained it at a low level for a long
time. To further understand the effects of the coordination of carbon and nitrogen
metabolism on the source-sink relationship in potato, we designed splitting application
of nitrogen under the same nitrogen application rate to study the changes of
carbon/nitrogen ratio. The results showed that, applied a small amount of nitrogen (50
mg N/kg soil) at transplanting and added a lot of nitrogen (200 mg N/kg soil) at tuber
formation not only helped to decrease the carbon/nitrogen ratio before tuber bulking,
but also helped to decrease it during the tuber bulking stage. These decreases
coordinated the relationship between carbon and nitrogen metabolism during the whole
growing period in potato, prolonged leaf life time, improved the photosynthetic rate,
maintained plant source capacity a high level for a long time, and then increased the whole plant dry matter accumulation, ultimately increased tuber yield. It suggests that
different water and nitrogen levels and split application of nitrogen affected the
carbon-nitrogen metabolism coordination to affect plant source capacity, and then
influenced tuber yield. Reasonable water and nitrogen management coordinated the
relationship between carbon and nitrogen metabolism, maintained plant source capacity
at a high level, thereby increased tuber yield, water and nitrogen use efficiency.
Key words: potato; yield; source-sink relationship; water; nitrogen |
修改评论