PubMed · 15413515
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G LILJESTRAND. 1950-03-27. Krogh, August.. https://doi.org/10.1111/j.1748-1716.1950.tb00688.x
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Grapes are grown in semiarid environments, where drought and salinity are common problems. Microarray transcript profiling, quantitative reverse transcription-PCR, and metabolite profiling were used to define genes and metabolic pathways in Vitis vinifera cv. Cabernet Sauvignon with shared and divergent responses to a gradually applied and long-term (16 days) water-deficit stress and equivalent salinity stress. In this first-of-a-kind study, distinct differences between water deficit and salinity were revealed. Water deficit caused more rapid and greater inhibition of shoot growth than did salinity at equivalent stem water potentials. One of the earliest responses to water deficit was an increase in the transcript abundance of RuBisCo activase (day 4), but this increase occurred much later in salt-stressed plants (day 12). As water deficit progressed, a greater number of affected transcripts were involved in metabolism, transport, and the biogenesis of cellular components than did salinity. Salinity affected a higher percentage of transcripts involved in transcription, protein synthesis, and protein fate than did water deficit. Metabolite profiling revealed that there were higher concentrations of glucose, malate, and proline in water-deficit-treated plants as compared to salinized plants. The metabolite differences were linked to differences in transcript abundance of many genes involved in energy metabolism and nitrogen assimilation, particularly photosynthesis, gluconeogenesis, and photorespiration. Water-deficit-treated plants appear to have a higher demand than salinized plants to adjust osmotically, detoxify free radicals (reactive oxygen species), and cope with photoinhibition.
Genotypic variation for water status and gas exchange parameters under different water treatments (well-watered and water-stressed plants before and after rehydration) were investigated in a population of recombinant inbred lines (RILs) of sunflower (Helianthus annuus L.). Afterwards, four RILs and parental lines presenting contrasting responses to dehydration and rehydration were selected to determine the differential expression of four water-stress associated genes: aquaporin, dehydrin, leafy cotyledon1-like protein and fructose-1,6 bisphosphatase. Water stress revealed a high genetic variability for water status and gas exchange parameters when compared with well-watered genotypes. Genetic gain when selected RILs were compared with the best parent was significant for most traits due to transgressive segregation. QTL mapping and graphical genotyping showed that RILs carrying different genomic regions for some QTLs presented also physiological different characteristics as well as gene expression patterns. The expression level of aquaporin genes in leaves of four RILs and their parents was down regulated by water stress and was associated with relative water content (RWC). Down-regulation was also associated with genomic regions having alleles with negative effects on plant water status. The level of dehydrin transcripts increased in leaves of all studied RILs in response to water stress. Transcript accumulations of dehydrin and leafy cotyledon1-like genes, likely involved in protective tolerance processes, were not correlated directly with plant water status or QTL effects. Down-regulation of fructose-1,6 bisphosphatase was observed under water stress. Net photosynthesis rate (P(n)) and the fructose-1,6 bisphosphatase gene expression levels were associated mainly after rehydration. This phenomenon indicates an association between physiological response to water stress and differential expression of water-stress related genes.
The high water content of sewage biosolids makes them expensive to transport. Two experiments were done to see if it was practical to use transpiration by plants as a low cost method to dehydrate biosolids. (i) To assess biosolids as a growth-medium for plants, maize, beans, pumpkin, forage oats and an annual ryegrass were grown in pots of fresh biosolids. Plant growth varied between species and potassium deficiency was found to be a limiting factor for barley. Roots were slow to penetrate anoxic biosolids in the bottom of the pots. (ii) Dehydration rates were measured in 30 litre boxes of biosolids from two different sources. Boxes were planted with maize or beans, or kept fallow. Despite the high (73-83%) initial water content of the biosolids, plants were susceptible to wilting on warm days which suggested that a significant proportion of the water in biosolids is not freely available to plants. Shrinkage caused a major reduction in biosolids volume in both experiments. When change in volume of the biosolids residue was accounted for, there was a 56% average water loss in planted treatments and 34% water loss in the fallow treatment. This indicates that planting may have some potential as a technique to accelerate dehydration of biosolids. Water contents were not reduced sufficiently to influence biosolids microbial populations.