Page 223 - PC2019 Program & Proceedings

PLANT CANADA 2019

P19. Temporal shifts in oxidative stress and fermentative metabolites are associated with
physiological injuries in postharvest pear fruit
1
2
1
1
1
Flaherty, E. ; G. Lum ; J. DeEll ; S. Subedi ; B. Shelp ; Bozzo, G.
3
1 University of Guelp
2 Ontario Ministry of Agriculture, Food and Rural Affairs
3 Binghamton University-State University of New York
The fresh market period for European pear (Pyrus communis L.) fruit can be extended by their storage at
low temperature under controlled atmosphere (CA; which includes low O2 and/or elevated CO2 partial
pressures). A complementary practice involves the application of the ethylene antagonist, 1-
methylcyclopropene (1-MCP). Both practices limit ripening events, such as softening and peel yellowing,
which are simultaneous with endogenous ethylene production. Unfortunately, 1-MCP and CA can
promote the occurrence of physiological injuries (e.g., internal breakdown and cavities of the flesh)
during storage. Herein, we investigated whether the occurrence of physiological injuries in stored pears is
correlated with altered oxidative stress and fermentative metabolite profiles. ‘AC Harrow Crisp’ pears
were treated with or without 1-MCP, and then held at 0 °C under refrigerated air or CA; disorder
symptoms and metabolites were assessed in all stored fruit. Senescent scald and internal breakdown were
most evident in non-1-MCP-treated fruit stored under refrigerated air, but limited by 1-MCP and CA.
Internal breakdown and senescent scald were associated with the accumulation of citrate and fumarate,
respectively. Internal cavities were evident in 1-MCP fruit held under CA, which coincided with the
accumulation of 4-aminobutyrate and alanine. All disorders were linked to antioxidant depletion within
the fruit. In summary, the temporal shifts in oxidative stress and fermentative metabolites are key
indicators of postharvest stresses that promote the deterioration of pears.

Gale G. Bozzo (gbozzo@uoguelph.ca)

P20. A novel method for irrigating plants, tracking plant water use and imposing water deficits on
plants grown in artificial environments
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Bruch, A. ; H. Earl
University of Guelph

Gravimetric methods for measuring single plant water use and simulating drought stress involve frequent
weighing and watering of pots. This is labour intensive, requiring heavy lifting on a daily basis over the
course of weeks. Here, we describe a novel, non-gravimetric system that address these
shortcomings. Each plant is grown in a 110-cm tall, 10-cm diameter tube filled with a mixture of fine
turface and granitic sand. The tube is divided into an upper rooting section and a lower wicking bed
section by a nylon mesh barrier that prevents root incursion into the lower section, but maintains capillary
connectivity. As the plant dries the soil in the rooting section, the water is rewetted passively from the
lower section. A float valve fed by a reservoir ensures that the water table in the lower section is
maintained at a set height, and so water depletion from the reservoir serves as a measure of cumulative
plant water use. Drought stress can be induced by repositioning the float valve to drop the water table in
the lower section. This soil mixture displays an unusually steep reduction in volumetric soil water content
(VSWC) with a small change in gravimetric potential, so lowering the water table reduces VSWC of the
rooting section enough to induce a significant stress, reducing soybean plant water use by 53%, and plant
biomass by 50%.

Austin Bruch (brucha@uoguelph.ca)

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