Articles
INFLUENCE OF IRRIGATION AND NITROGEN FERTILIZATION ON BROCCOLI POLYPHENOLICS CONCENTRATION
Article number
856_6
Pages
55 – 62
Language
English
Abstract
Polyphenolics are phytochemical compounds that may be beneficial or toxic to humans.
They are found in fruits and vegetables known for their health promoting characteristics.
These carbon-based secondary metabolites have roles such as protection against ultraviolet radiation, free radicals, oxidative stress, herbivores and pathogens.
Their synthesis in plant material is therefore linked to both biotic and abiotic stress sources.
Under nitrogen stress, for instance, an increase in polyphenolics concentration has been reported.
This behaviour has been exploited in the design and marketing of the Dualex, a new diagnostic instrument aimed at establishing the in-season requirements of crops for nitrogen (N) fertilizer.
The Dualex can estimate leaf polyphenolics concentrations from the measurement of ultraviolet (UV, 375 nm) absorption of the leaf epidermis by the double excitation of chlorophyll fluorescence.
The value of the UV absorbance is directly connected to the amount of leaf polyphenolics.
The objective of this study was to determine if irrigation and nitrogen fertilization can influence broccoli polyphenolics concentrations.
A broccoli experimental field was established in 2005 at the Agriculture and Agri-Food Canada experimental farm of LAcadie (Quebec). The crop was fertilized with either 0, 105, 135, 165, 195 or 225 kg N/ha and provided or not with supplementary irrigation after crop establishment.
Four Dualex measurement campaigns were made, from 26 to 47 days after planting, as well as one laboratory estimation of polyphenolics.
The absence of irrigation increased significantly polyphenolics concentrations on the two last dates (by 36 and 35%, respectively). The increase in fertilizer N was related to a linear or curvilinear decrease in polyphenolics.
At the last date, unfertilized plots had 86 and 16% higher polyphenolics than fully fertilized ones, in irrigated and non-irriguated plots, respectively.
Yields of marketable heads increased in a curvilinear matter with N rate, with a tendency to plateau at high rates.
The percent of hollow stem was increased at high N rates, only under the irrigated treatment.
Plots placed under conditions to produce the highest possible polyphenolics content were however the least productive ones, from a fresh market standpoint.
Since these stresses are impacting crop growth and development, there is a clear antagonism between the production of polyphenolics from broccoli, on one hand, and fresh market production, on the other hand.
The Dualex has the potential to establish broccoli N requirements by its capacity of detecting polyphenolics concentration in leaves but irrigation may interfere in the diagnosis.
They are found in fruits and vegetables known for their health promoting characteristics.
These carbon-based secondary metabolites have roles such as protection against ultraviolet radiation, free radicals, oxidative stress, herbivores and pathogens.
Their synthesis in plant material is therefore linked to both biotic and abiotic stress sources.
Under nitrogen stress, for instance, an increase in polyphenolics concentration has been reported.
This behaviour has been exploited in the design and marketing of the Dualex, a new diagnostic instrument aimed at establishing the in-season requirements of crops for nitrogen (N) fertilizer.
The Dualex can estimate leaf polyphenolics concentrations from the measurement of ultraviolet (UV, 375 nm) absorption of the leaf epidermis by the double excitation of chlorophyll fluorescence.
The value of the UV absorbance is directly connected to the amount of leaf polyphenolics.
The objective of this study was to determine if irrigation and nitrogen fertilization can influence broccoli polyphenolics concentrations.
A broccoli experimental field was established in 2005 at the Agriculture and Agri-Food Canada experimental farm of LAcadie (Quebec). The crop was fertilized with either 0, 105, 135, 165, 195 or 225 kg N/ha and provided or not with supplementary irrigation after crop establishment.
Four Dualex measurement campaigns were made, from 26 to 47 days after planting, as well as one laboratory estimation of polyphenolics.
The absence of irrigation increased significantly polyphenolics concentrations on the two last dates (by 36 and 35%, respectively). The increase in fertilizer N was related to a linear or curvilinear decrease in polyphenolics.
At the last date, unfertilized plots had 86 and 16% higher polyphenolics than fully fertilized ones, in irrigated and non-irriguated plots, respectively.
Yields of marketable heads increased in a curvilinear matter with N rate, with a tendency to plateau at high rates.
The percent of hollow stem was increased at high N rates, only under the irrigated treatment.
Plots placed under conditions to produce the highest possible polyphenolics content were however the least productive ones, from a fresh market standpoint.
Since these stresses are impacting crop growth and development, there is a clear antagonism between the production of polyphenolics from broccoli, on one hand, and fresh market production, on the other hand.
The Dualex has the potential to establish broccoli N requirements by its capacity of detecting polyphenolics concentration in leaves but irrigation may interfere in the diagnosis.
Authors
E. Fortier, Y. Desjardins, N. Tremblay, C. Bélec, M. Côté
Keywords
crop management, Dualex, hollow stem, stress, yield
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