|
The importance of mineral nutrients to crop
production has been recognized for more than 2000
years. Plant mineral nutrition is unique because
green plants, the only multicellular autotrophic
organisms, can mine inorganic elements from the
environment without having to rely on high-energy
compounds synthesized by other organisms Earlier
this century, classical physiological research
into the processes involved in mineral nutrient
acquisition was a major research focus in the
field of plant biology. Recently, there has been
a great upsurge in research and a renewed interest
in the field of plant mineral nutrition now that
contemporary experimental approaches in membrane
biophysics, molecular biology, and plant physiology
are being used to dissect the mechanisms underlying
transport and utilization of mineral ion nutrients.
We currently are witnessing an exciting period
of research into plant mineral ion transport.
Many new molecular approaches have allowed the
cloning of families of mineral ion transporters,
and microelectrode technologies have allowed us
to study the functions of these individual transporters,
both when expressed in heterologous systems and
when studied in planta. The challenge now at hand
is to fit these individual pieces back together
to begin to understand the molecular physiology
of the intact plant, in terms of the mechanisms
and regulation of mineral nutrient acquisition
and utilization.
This chapter focuses
on recent findings concerning the molecular physiology
of macronutrient and micronutrient transport as
well as the strategies plants use to tolerate
stressful soil environments such as toxic concentrations
of metals in the soil. Emphasis will be on those
essential mineral elements, such as potassium
(K) and iron (Fe), for which researchers are beginning
to understand the molecular mechanisms of plant
acquisition and transport. Recent experimental
and technological advances that have enabled researchers
to clone the genes encoding mineral ion transporters
will also be described.
Many topics related
to mineral nutrition have been addressed in other
chapters of this text. Plant uptake and assimilation
of nitrogen and sulfur, for example, are discussed
in Chapters 8 and 16, respectively. Anabolic and
catabolic reactions involving the most abundant
mineral nutrients—carbon, hydrogen, and oxygen—appear
throughout the text and constitute the primary
focus of Chapters 12 through 14. Long-distance
transport of selected mineral nutrients is discussed
in Chapter 15.
|
