Effects Of Cold Water Stress At Tillering Stage On Physiological Characteristics And Yield Of Japonica Rice In Cold Region

Heilongjiang Province is the most important production area for japonica rice in cold regions.Its high and stable yields play an important role in China's food security.Low temperature cold damage is one of the major natural disasters in Heilongjiang area.Affected by low temperature,agricultural development in Heilongjiang area has been affected to a certain extent.limit.The development of the tillering stage is the key period during rice growth,and the temperature has a significant impact on the tillering stage;if it encounters low temperature and cold damage during this period,it will have a greater impact on the growth and development of rice,which will lead to slow growth of the plant,a serious decline in the number of tillers The number of chloroplasts in the leaves is reduced,photosynthesis is weakened,the number of effective panicles and total grains are reduced,and ultimately the yield is reduced.The test materials used in this experiment were Dongnong 428 and Songjing No.10,which carried out related research on their growth and development by simulating the low temperature cold damage under natural conditions,using cold water stress.Mainly to study the growth and development,photosynthetic characteristics,leaf ultrastructure,functional leaf and root antioxidant systems,osmotic adjustment substances,endogenous hormones,dry matter accumulation and transport of cold area japonica rice under cold water stress at different days,and cold area japonica rice Yield formation rules,clarify the response mechanism of cold-region japonica rice physiological characteristics to cold water stress,and enrich the cold-tolerance research of cold-region japonica rice.The test results are as follows:?1?Cold water stress at the tillering stage significantly inhibited rice growth.Compared with D0?Contrast?,the plant height and number of tillers of Songjing 10 and Dongnong 428 were affected by the cold water stress at the tillering stage,and the greater the degree of influence with the extension of cold water stress time.The effect of 5 days cold water treatment on the plant height and tiller number of rice was not significant,and 10-15 days cold water treatment extended the plant height and tiller growth time.Under the cold water stress at the tillering stage,the plant height and tiller number of Dongnong 428 decreased less than Songjing 10,and the gap continued to increase with the extension of stress time.?2?Compared with D0,root length density,root volume,root surface area and root average of japonica rice in cold region under tillering stage under cold water stress period Both diameters decreased,and the decrease rate increased with the increase of cold water stress time,and there were differences between treatments.The above indexes of Dongnong 428 cold water stress 5 days cold japonica rice were not significantly different;Songjing 10 and Dongnong 428 cold water stress decreased significantly under 10-15 days.Under cold water stress at the tillering stage,Dongnong428's root length density,root volume,and root surface area decreased less than Songjing 10,and the gap continued to increase with the extension of stress time.?3?Compared with D0,the vigor of japonica rice roots in cold regions under tillering stage cold water stress decreased,and the decrease rate increased with the increase of cold water stress time,and there was a difference between treatments.The above-mentioned indexes of japonica rice in cold areas under cold water stress for 5 days were not significantly different;cold water stress decreased significantly under 10-15 days.Under the cold water stress at the tillering stage,Dongnong 428's root activity decreased less than Songjing 10,and the gap increased with the extension of stress time.After the cold water ended,Dongnong 428's root vitality increased more than Songjing 10.?4?Compared with D0,the MDA,O₂^-,H₂O₂ content and SOD,POD,and CAT activity of cold-season japonica rice functional leaves and roots increased with the extension of cold water stress under cold water stress at the tillering stage,and there were differences between treatments.The contents of MDA,O₂^-and H₂O₂ in Dongnong 428 functional leaves and roots were lower than Songjing 10,and the activities of SOD,POD and CAT in Dongnong 428 functional leaves and roots were higher than Songjing 10,and with the extension of cold water stress time The gap widens.After the end of cold water,compared with Dongnong 428,the antioxidant enzyme activity of Songjing 10 functional leaves and roots decreased more rapidly,and the content of MDA,O₂^-,and H₂O₂ decreased more slowly.The antioxidant enzyme activity of functional leaves in cold region japonica rice was faster than that of root stress,and the degree of damage was lower.?5?Compared with D0,the contents of Pro,SS and SP of functional leaves and roots of cold-land japonica rice in the tillering stage under cold water stress increased significantly,and the increase rate increased with the increase of cold water stress time.There were differences between treatments.The accumulation of Pro and SS in Dongnong 428 root system was not significantly different from that of Songjing 10 under each treatment,but the SP content of its root system was significantly different from Songjing 10 in each treatment.Dongnong 428 functional leaves Pro,SS and SP were significantly different from Songjing 10 under each treatment.After the end of cold water,compared with Dongnong 428,Songjing 10 functional leaves and root osmotic adjustment substances decreased faster,and the content of Pro,SS,SP of functional leaves was more significant than that of roots.?6?Compared with D0,under cold water stress at the tillering stage,the ultrastructure of japonica rice leaves in cold regions was destroyed.With the extension of cold water stress time,the degree of damage was more serious,and there were differences between the treatments.Under each cold water treatment,Dongnong 428 had less damage to the ultrastructure of the leaves than Songjing 10.Especially in the cold water treatment for 10-15 days,the chloroplast structure of Songjing 10 was seriously damaged,the osmium grains increased,and the starch grains were digested.Nong 428 had the above situation only after 15 days of cold water treatment,and a small amount of starch granules were kept in the chloroplast.?7?Compared with D0,under cold water stress at the tillering stage,the leaf area index index of japonica rice in cold regions decreased significantly,and it decreased significantly with the extension of cold water stress time.At the same time,the total amount of chlorophyll a,chlorophyll b,chlorophyll and Pn,Tr,Gs,and Ci of cold-land japonica rice decreased,and the decreased leaves decreased with the extension of cold water stress,and there were differences between the treatments.It can be seen that the changes in leaf area index,photosynthetic parameters and photosynthetic hormone content are synchronized.It can be seen that the significant decrease in leaf area index is one of the main reasons for the decrease in chlorophyll content and photosynthetic parameters of japonica rice in cold regions under the tillering stage under cold water stress.?8?Compared with D0,the content of IAA,GA₃,ZR in cold leaves of cold-land japonica rice at the tillering stage was significantly decreased,which decreased significantly with the extension of cold water stress time,while the content of ABA increased significantly,with cold water stress The time increased significantly and there was a difference between treatments.Dongnong 428 functional leaf and root ABA increased less than cold-sensitive Songjing 10,while functional leaf and root IAA,GA₃,ZR decreased less than Songjing 10.It can be seen that the changes of endogenous hormones in cold area japonica rice are different,and the changes in content can alleviate the damage of low temperature to cold area japonica rice,of which Songjing 10 has weak antioxidant capacity.?9?Compared with D0,under cold water stress at the tillering stage,the roots,stems,leaves,panicle dry weight,total dry weight,population growth rate,dry matter transport amount before flowering,after flowering in cold season japonica rice at each growth stage Dry matter accumulation,stem-sheath material output rate and stem-sheath material contribution rate decreased significantly with the extension of cold water stress time,and there were significant differences among treatments.Dongnong under cold water stress at tillering stage 428 had a smaller drop in dry weight below ground,dry weight above ground and total dry weight than Songjing 10.?10?Compared with D0,the yield and components of yield of japonica rice in cold regions under cold water stress at the tillering stage both decreased,and the decrease rate varied with the treatment.The time increases.The decrease of Dongnong 428 output and its components are lower than that of Songjing 10.Among them,the decrease range of Songnong 10 and Dongnong 428 are13.39%?42.99%and 8.33%?36.9%respectively.The main reason for the drop in yield during the tillering stage under cold water stress is the decrease in the number of available ears.The reason why Dongnong 428 is more cold tolerant than Songjing 10 is that Dongnong 428's higher antioxidant enzyme activity and osmotic adjustment substances make Dongnong 428's functional leaves and roots more capable of scavenging active oxygen and products under cold water stress,and enhance the plant Cold tolerance is less damaged,resulting in stronger respiration and photosynthesis,resulting in greater production capacity of photosynthetic products and greater accumulation of dry matter,which ultimately leads to lower yields than Songjing 10.