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ARS Home » Northeast Area » Kearneysville, West Virginia » Appalachian Fruit Research Laboratory » Innovative Fruit Production, Improvement, and Protection » Research » Publications at this Location » Publication #324145
Title: Dry matter partitioning and photosynthetic response to biennial bearing and freeze damage in 'Empire' apple

Author
item Glenn, David

Submitted to: Scientia Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/30/2016
Publication Date: 7/18/2016
Citation: Glenn, D.M. 2016. Dry matter partitioning and photosynthetic response to biennial bearing and freeze damage in 'Empire' apple. Scientia Horticulturae. 210:1-5.

Interpretive Summary: Biennial cropping is typically characterized as having 'ON' and 'OFF' years in which the 'ON' year produces an excessive crop load and the 'OFF' year has a very small crop load. However, frost damage during the bloom period or winter freeze damage are another means of reducing the crop load that can initiate biennial bearing in an otherwise consistent cropping system. The objectives were to determine what effect single and multiple year crop loss had on the current and subsequent year’s dry matter partitioning and photosynthesis. Dry matter partitioning and whole tree photosynthesis (A) were measured in biennial bearing 'Empire' apple trees when two consecutive frosts occurred following an 'OFF' year. Frost events reduced fruit dry weight to levels equivalent to the 'OFF' years, but the 'SUPPRESSED' years (one 'OFF', and one or two frost years) reduced partitioning to wood dry matter and leaf + fruit more than the 'OFF' years, while increasing the fruit dry matter partitioning compared to the 'OFF' years despite similar fruit yield and crop load. The 'ON' years had the highest mean daily A (3.8 µmol/m2/s), 'SUPPRESSED' years were intermediate (3.0 µmol/m2/s) and the 'OFF' years had the lowest A (2.5 µmol/m2/s). It appears that in years when fruiting is suppressed more than a single year, dry matter partitioning to wood is also suppressed and a great partitioning occurs to the remaining fruit and leaf tissue. This may be a response to a continued deficit of the hormonal complex supplied by fruit as they develop.

Technical Abstract: Biennial cropping is typically characterized as having 'ON' and 'OFF' years in which the 'ON' year produces an excessive crop load and the 'OFF' year has a very small crop load. Frost damage during the bloom period or winter freeze damage are another means of reducing the crop load that can initiate biennial bearing in an otherwise consistent cropping system. The objectives were to determine what effect single and multiple year crop loss had on the current and subsequent year’s dry matter partitioning and photosynthesis. Dry matter partitioning and whole tree photosynthesis (A) were being measured in biennial bearing 'Empire' apple trees when two consecutive frosts occurred following an 'OFF' year. This provided an opportunity to evaluate two cycles of conventional biennial bearing and the effect of three years of suppressed crop load on dry matter partitioning and whole tree photosynthesis. Frost events reduced fruit dry weight to levels equivalent to the 'OFF' years, but the 'SUPPRESSED' years (one 'OFF', and one or two frost years) reduced partitioning to wood dry matter and leaf + fruit more than the 'OFF' years, while increasing the fruit dry matter partitioning compared to the 'OFF' years despite similar fruit yield and crop load. The 'ON' years had the highest fruit dry weight and percent dry weight partitioned to fruit and leaf + fruit. Conversely, the 'ON' year had the least leaf area index and percent dry weight partitioned to wood and leaf tissue. There were no differences in canopy area; however, the 'ON' years had a significantly reduced LAI. Radiation use efficiency [RUE; Annual biomass (kg)/PAR (MegaMoles/growing season) x canopy area (m2)] was linearly correlated with the percent dry mass partitioned to fruit and negatively correlated with LAI. For a specified LAI, the 'ON' year had a greater RUE than the 'OFF' or 'SUPPRESSED' years, and there were no differences between 'OFF' and 'SUPPRESSED' years. Analysis of daily photosynthesis (A) indicated that all three treatments were significantly different. The 'ON' years had the highest mean daily A (3.8 µmol/m2/s), 'SUPPRESSED' years were intermediate (3.0 µmol/m2/s) and the 'OFF' years had the lowest A (2.5 µmol/m2/s). It appears that in years when fruiting is suppressed more than a single year, dry matter partitioning to wood is also suppressed and a great partitioning occurs to the remaining fruit and leaf tissue. This may be a response to a continued deficit of the hormonal complex supplied by fruit as they develop.