Objective: In the operational reality of protected grape cultivation within controlled environments, the exuberant photosynthetic metabolism often encounters challenges due to inadequate CO2 provision, resulting in diminished photosynthetic activity and consequent compromises in grape quality, potentially leading to decreased yields. Conventional CO2 fertilization practices within these facilities frequently suffer from issues such as uneven application and exorbitant costs. Furthermore, the optimal CO2 concentration conducive to grape cultivation under protected conditions remains undetermined, thereby rendering the precise regulation of CO2 fertilization a persistent challenge within contemporary greenhouse operations. This thesis introduces a novel approach by integrating CO2 fertilization with aeration irrigation techniques, proposing a CO2-aeration irrigation fertilization paradigm. Through a comprehensive examination of diverse CO2 fertilization modalities and concentrations and their impacts on grape photosynthetic parameters, yield metrics, and fruit quality attributes, this thesis aims to ascertain the viability of the CO2-aeration irrigation fertilization paradigm. Additionally, it endeavors to identify the optimal CO2 concentration requisite for protected grape cultivation. This provides a theoretical basis for the future application of aeration irrigation technology under controlled conditions for greenhouse grape production.
Methods: This study used 5-year-old ‘Flame Seedless’ grapes as test materials. To explore the best CO2 fertilization method and the most suitable CO2 concentration for greenhouse grape production, three different aeration methods were set: intelligent aeration (new CO2 aeration mode, IW), traditional aeration (CO2 reaction bag, TW), and no aeration (control group, CK), along with four different concentration treatments of 500ppm (CO2 concentration of 500 ± 30 µmol·mol-1), 700ppm (CO2 concentration of 700 ± 30 µmol·mol-1), 850ppm (CO2 concentration of 850 ± 30 µmol·mol-1), and 1000ppm (CO2 concentration of 1000 ± 30 µmol·mol-1).
Results:
(1) The novel CO2 aeration method combined with the subsurface drip irrigation system significantly improved the chlorophyll content and photosynthetic characteristics of grape leaves. Within the same irrigation cycle, the grape light saturation point, apparent quantum efficiency, and maximum net photosynthetic rate all reached their maximum values under the new CO2 fertilization method, while the light compensation point was lower than the other treatments. Additionally, this method significantly enhanced the leaf CO2 saturation point, CO2 compensation point, SOD, CAT, POD, PPO, and Rubisco activity, with the highest grape yield reaching 13875.61 kg·hm-2.
(2) CO2 concentrations of 700 ppm and 850 ppm significantly increased the chlorophyll content of grape leaves and significantly reduced the chlorophyll a/b ratio; at 700 ppm, the net photosynthetic rate and water use efficiency of grape leaves were the highest. The grape light saturation point and apparent quantum efficiency reached their maximum values at a CO2 concentration of 850 ppm, followed by 700 ppm. Moreover, at 700 ppm, the maximum net photosynthetic rate, SOD, CAT, POD, PPO, and Rubisco activity were significantly increased, with the highest grape yield reaching 14541.37 kg·hm-2.
(3) The novel CO2 aeration method combined with the subsurface drip irrigation system significantly improved the quality of grape fruits, increasing the degree of fruit coloring. It also increased the content of phenolic compounds in the fruit skin. At CO2 concentrations of 700 ppm and 850 ppm, the soluble solids content, soluble sugar content, and hundred-grain weight of grape fruits were significantly increased, while the titratable acid content was reduced. At 700 ppm, the total chlorophyll and carotenoid content in grape skin were the lowest. At CO2 concentrations of 700 ppm and 850 ppm, the color index of ripening grape fruits (CIRG) reached 4.79 and 4.45, respectively, with the highest flavonoid, anthocyanin, and total phenolic content in the fruit skin at 700 ppm.
Conclusion: Supplementing CO2 significantly enhanced the photosynthetic pigment content and photosynthetic performance of greenhouse grape leaves, promoted fruit coloration, and improved grape yield and quality. Among these, the effect of the novel CO2 enrichment method surpassed that of the traditional CO2 enrichment method. In experiments comparing different CO2 concentrations, the optimal enhancement of photosynthetic characteristics, yield, and fruit quality in greenhouse grapes was observed at CO2 concentration of 700 ppm.
谷歌
火狐
