Effects Of CO₂ Enrichment In Different Periods On Physiological Characteristics And Fruit Growth Of Greenhouse Tomato

In order to study the effect of carbon dioxide enrichment on the growth physiological characteristics and fruit growth of greenhouse tomatoes,this experiment uses tomato CM160 as the test material,and is divided into two parts:carbon dioxide enrichment at the seedling stage and carbon dioxide enrichment at the later stage of the treatment level.There are two treatments for enriching carbon dioxide at the seedling stage,namely,no CO₂ enrichment（CK）and CO₂ enrichment treatment.At the seedling stage,there are a total of four treatments for the enrichment of carbon dioxide in the late stage,namely enrichment of CO₂ （A）in the seedling stage,enrichment of CO₂ （B）in the entire period,enrichment of CO₂ （C）in the later stage of colonization,and no enrichment in the entire period.Enrich CO₂ （D）.The temperature in the seedling stage test was controlled at about22℃,and the CO₂ concentration was controlled at 600±50（?）l·L^-1.The later tests were all high-temperature environments,the temperature was controlled at about 37℃,and the CO₂ concentration was controlled at 950±50（?）l·L^-1.According to the above experimental treatments,the following conclusions were drawn by studying the growth of greenhouse tomato seedlings with CO₂ enrichment and the effects of CO₂ enrichment on the growth and physiological characteristics and yield of greenhouse tomato under high temperature conditions in the later stage:（1）Enriching CO₂ in the tomato seedling stage can increase the plant height,stem thickness and leaf area of tomato seedlings,but the increase was not significant in the early stage,and it increased significantly from 21 days.The photosynthesis and SPAD value of tomato increased by increasing CO₂ ,and the dry and fresh weight of the above ground and root of tomato seedlings,and the root vigor of the tomato seedlings all increased compared with the control,but not significant.Increasing CO₂ application increased the root-to-shoot ratio and strong seedling index,but the root length increased in the early stage and decreased in the later stage.（2）Increasing the application of CO₂ in different periods increased the plant height,stem thickness and leaf area of tomato.Plant height and stem thickness of each treatment showed from high to low CO₂ enrichment in the whole period>CO₂ enrichment in the seedling stage>CO₂ enrichment in the late colonization period>no CO₂ enrichment in the entire period.From high to low,the leaf area showed that the enrichment of CO₂ during the whole period>the enrichment of CO₂ at the later stage of colonization>the enrichment of CO₂ at the seedling stage>the absence of CO₂ enrichment.There is basically no difference in growth index between enriched CO₂ at the seedling stage and enriched CO₂ only at the later stage.The plant height,stem thickness and leaf area of??the treatment with CO₂ enrichment during the whole period are the largest,which is significantly higher than that of the control.（3）Enriching CO₂ in different periods can increase the net photosynthetic rate of tomato,increase the concentration of intercellular carbon dioxide,decrease the stomatal conductance,and increase the content of chlorophyll a,chlorophyll b and total chlorophyll.The photosynthetic characteristics of tomatoes increased with increasing CO₂ .Net photosynthetic rate,from high to low intercellular carbon dioxide concentration for the entire period enriched with CO₂ >later enriched with CO₂ >enriched with CO₂ at seedling stage>no enriched with CO₂ ,stomatal conductance from high to low without enriched with CO₂ >seedling stage CO₂ enrichment>CO₂ enrichment only in the later period>CO₂ enrichment throughout the period.The content of chlorophyll showed as CO₂ enrichment during the whole period>CO₂ enrichment only in the later stage>CO₂ enrichment at the seedling stage>CO₂ enrichment without CO₂ enrichment.The enrichment of CO₂ during the whole period was higher than that of CO₂ enrichment only in the later stage,but the photosynthetic index and chlorophyll content were higher,but the difference was not significant.The enrichment of CO₂ in the seedling stage promoted more than no enrichment of CO₂ ,but the difference was not significant.The results showed that enrichment of CO₂ under high temperature conditions increased the photosynthesis of plants,but there was no significant difference between enrichment of CO₂ and no enrichment of CO₂ at the seedling stage under high temperature conditions.（4）Increasing the application of CO₂ in different periods can increase the antioxidant enzyme activity of tomato and reduce the osmotic adjustment substances.During the whole period,the SOD,POD,CAT,PPO and other antioxidant enzyme activities of CO₂ enriched tomato leaves were the highest,and the MDA content was the lowest,but there was no significant difference from the CO₂ enriched antioxidant enzyme activity in the later stage.The increase of antioxidant enzymes in the high temperature environment without carbon dioxide enrichment also reduces the damage of high temperature to tomatoes and membrane lipid peroxidation damage.CO₂ enrichment significantly promotes the increase of soluble protein and leaf proline content of tomato plants,helps restore tomato plant functions,improves normal cell activity,and enhances tomato plant resistance.（5）Increasing the application of CO₂ at any period increases the quality of tomatoes.Increasing the application of CO₂ increases the content of soluble sugar,soluble protein,and vitamin C in tomato fruits to varying degrees.The titratable acid content will decrease,and the soluble sugar content during the color conversion period will be the highest.,The titratable acid content is the least,the sugar-acid ratio is the largest in the red ripe period,and the increase of CO₂ during the whole period has the greatest impact on tomato quality.Increasing the application of CO₂ reduces the fruit hardness of tomatoes in different ripening periods.As the tomatoes mature,the hardness of the tomatoes gradually decreases.The increased application of CO₂ during the entire period has a lower hardness than the other two treatments.Generally speaking,the increase of CO₂ during the entire period has the best effect,The fruit quality is the best,but the various indicators are not significantly different compared with only increasing CO₂ in the later stage.The fruit quality with CO₂ enrichment at seedling stage is higher than that without CO2 enrichment,but the difference is not significant.（6）Regardless of the period of increasing CO₂ application,the horizontal and vertical diameter of the fruit,the number of flowering,the number of fruiting,and the fruit setting rate will increase,the weight of each fruit,the yield per plant and the total yield will increase,and the final total yield will be enriched in CO₂ throughout the period.The production of enriched CO₂ only in the later stage and enriched CO₂ in the seedling stage increased by 50.7%,36.3%,11.6%,respectively.This shows that the increased application of CO₂ in different periods promotes tomato yield and economic benefits.The increase in production showed that CO₂ enrichment during the whole period>CO₂ enrichment only in the later stage>CO₂ enrichment at the seedling stage>CO₂ enrichment at the seedling stage.Experimental studies have shown that the increased application of CO₂ gas fertilizer can effectively promote the photosynthesis of tomatoes,increase production and improve quality.In particular,continuous enrichment of carbon dioxide during the entire growth period of tomato can significantly promote plant growth and fruit growth.If enrichment of CO₂ in the seedling stage does not increase enrichment in the later stage,it will not significantly promote the growth of tomatoes,so only in the seedling stage Enriching CO₂ has no significant effect.