Heavy metal ATPases

This group of enzymes catalyses a diverse set of functions in the homeostasis of essential heavy metals such as Cu2+, Zn2+, Mn2+, Fe2+, Ni2+ and Co2+ (Hussain et al., 2004 Williams and Mills, 2005). Heavy metal ATPases (HMAs) are members of the P-type ATPase superfamily and are also named CPx-ATPases due to a signature domain consisting of a cysteine-proline-x motif, where x is a cysteine, a histidine or a serine. The CPx motif resides in the sixth TMD and is thought to play a role in binding...

Synopsis

There is a wide range of inorganic and organic solutes in plants. Chapter 2 is an introduction to methods for their extraction and analysis. Inorganic elements can be measured by optical properties (by flame emission and atomic absorption spec-troscopy), mass spectroscopy, X-ray fluorescence, with ion-specific electrodes, and by ion chromatography. Analysis of organic solutes is usually achieved by chro-matographic separation, often in conjunction with mass spectroscopy and nuclear magnetic...

Free energy and the properties of solutions

In biological systems, the largest flow of water is from soil, through plants to the atmosphere - the so-called soil-plant-atmosphere continuum. Under natural conditions, liquid water enters the system following rainfall - it may be distant rainfall with subsequent surface or subsurface flow, but precipitation of liquid water starts the cycle - and water ends up in the gas phase, in the atmosphere. Little (only about 2 see Munns, 2005) of the water flowing in the system is retained in plants....

Accumulation and net uptake

The concentration and net accumulation of solutes within tissues can be used to imply transport across membranes. For instance, digested tissue (or tissue extract) can be screened (see Section 2.2) in a high-throughput manner using flame photometry, ion chromotagraphy or ion-coupled mass spectrometry to identify transport mutants with particular ion profiles (Salt, 2004). Infiltration-centrifugation of samples is used to extract apoplastic-enriched solution, which can be similarly screened to...

Nutrient acquisition

Ammonium Transporter

Many transporters are involved in the acquisition, storage and redistribution of macronutrients such as potassium, calcium, magnesium, nitrogen, sulphur andphos-phorus as well as micronutrients including iron, zinc, manganese and copper see also Chapter 12 . Depending on supply and demand of mineral nutrients, plants have to adjust the expression levels and activity of individual transporters to achieve a combination of specific transport properties affinity, substrate specificity and mode of...