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A large area trial involving four methods of soil fallowing (goat’s rue, traditional fallow, goat’s rue + brome grass, brome grass) was established in the spring 1996. This paper contains the results of our investigations concerning the content of macroelements in plants in the years 2000-2004. The weakest accumulation of nitrogen, potassium and magnesium by mono- and dicotyledonous plants occurred in the traditional fallow field; slightly richer concentration of the macroelements was determined in plants growing on the object sown with brome grass. Goat’s rue, both in a monoculture and mixed with brome grass, stimulated plants to accumulate more nitrogen, phosphorus, potassium and magnesium. Using goat’s rue to raise the content of macroelements in plants can prevent transfer of those elements to lower soil layers.
Desiccation-tolerant plants can be grouped into two categories: the 1) desiccation-tolerant plants whose internal water content rapidly equilibrates to the water potential of the environment and 2) the modified desiccation-tolerant plants that all employ mechanisms to retard and control the rate of water loss. Desiccation tolerance can be achieved by mechanisms that incorporate one of two alternatives, viz. cellular protection or cellular recovery (repair). The majority of plants probably utilize aspects of both. Desiccation-tolerant species, in particular the moss Tortula ruralis, appear to utilize a tolerance strategy that combines a constitutive protection system and a rehydration-inducible recovery mechanism. The rehydration-induced recovery mechanism of Tortula ruralis relies heavily upon a change in gene expression that is mediated by posttranscriptional events rather than the slower reacting transcriptional controls. Findings indicate that it takes a certain amount of prior water loss to fully activate the protein-based portion of the recovery mechanisms upon rehydration. Utilizing cDNAs representing individual hydrins (proteins whose synthesis is hydration specific) and rehydrins (proteins whose synthesis is rehydration specific), it was determined that if drying rates were slow rehydrin transcripts selectively accumulate in the dried gametophytes. Studies revealed that this storage involves the formation of mRNPs (messenger ribonucleoprotein particles). The identity and possible functions of the rehydrins of Tortula ruralis are also under investigation, in particular Tr155, a small rehydrin (24kD) appears to be involved in antioxidant production during rehydration.
Both urea and urease were subjects of early scientific investigations. Urea was the first organic molecule to be synthesized and jack bean urease was the first enzyme ever to be crystallized. About 50 years later it was shown to be the first nickel metalloenzyme. Since then, nickel-dependent ureases have been isolated from many bacteria, fungi and higher plants. They have similar structures and mechanisms of catalysis. A urease apoenzyme needs to be activated. This process requires participation of several accessory proteins that incorporate nickel into the urease forming catalytic site. In this review, ureases from various organisms are briefly described and the similarities of their structures discussed. Moreover, the significance of urea recycling in plants is explained and recent literature data about the function and activation of plant ureases are presented.
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