Agriculture Reference
In-Depth Information
very expensive and easily lixiviated to the environment, that can become
contaminated. In the long term, the best way to correct this deficiency is the
prevention by using tolerant genotypes and adequate crop management
techniques. In the case of pea, although Fe chlorosis is a worldwide
agricultural problem in this species, variability in tolerance exists among
different pea genotypes [8-13]. Accordingly, a number of pea breeding
programmes around the world have conducted screens for variation in Fe
deficiency tolerance and found significant variation for this trait. To further
improve the obtention of Fe chlorosis tolerant varieties, it is necessary to know
better which are the mechanisms involved in Fe acquisition and how are
regulated by plants.
To facilitate Fe acquisition, plants have developed different strategies.
Based on them, plants are classified in two categories: Strategy I plants, that
include non grasses plants, and Strategy II plants, that include the grasses
[1,14]. Strategy II plants favor the acquisition of Fe by releasing Fe 3+ chelating
agents (phytosiderophores) to soils (for recent information about Strategy II
plants, the reader is referred to [1]). Since pea belongs to the Strategy I plants,
we will describe Strategy I in more detail (see Fe acquisition in…).
Under Fe-deficient conditions, Strategy I plants induce morphological and
physiological changes in their roots, known as Fe responses, which favor Fe
acquisition. These responses are induced under Fe deficiency and are shut
down once plants acquire sufficient Fe, to avoid excess Fe accumulation and
energy lost. Their regulation is not totally known but in the last years evidence
has been accumulating suggesting that different hormones [ethylene, auxin and
nitric oxide (NO)] are involved in their activation while some Fe-related
signals, probably coming from shoots to roots through the phloem, would act
as inhibitors (see Regulation of Fe responses…).
In the study of the regulation of Fe responses in Strategy I plants is
important the use of two pea mutants with altered regulation of these
responses: brz ( bronze ) and dgl . Both mutants present constitutive activation
of Fe responses even when grown under Fe-sufficient conditions [15-19].
Consequently, both hyperaccumulate Fe in their vegetative tissues when
grown under Fe-sufficient conditions and can become intoxicated [17,19-20].
The genes related to the brz and dgl mutations have not been identified yet but
the research aimed to decipher them can open the way to a better knowledge of
the regulation of Fe acquisition in dicot plants (see Use of pea mutants…). This
knowledge would allow the obtention of more Fe-efficient genotypes and
seeds with higher Fe content.
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