Salt glands are important structural adaptations in some plant and animal species that are involved in the excretion of excess salts. Zoysia matrella is a highly salt tolerant turf grass that has salt glands. Two cultivars of Z. matrella, ‘Diamond’ and ‘Cavalier’, were examined in this study to look for salt gland related factors responsible for the differences in their degree of salt tolerance. In addition to the adaxial salt gland density being higher in ‘Diamond’, the salt glands in salt treated (300 mM NaCl) plants of this cultivar were bigger than the ones in ‘Cavalier’. ‘Diamond’, as well as some of the ‘Diamond’ x ‘Cavalier’ hybrid lines, showed a significant induction in salt gland density in response to salt treatment. Examination of salt gland density in ‘Diamond’ x ‘Cavalier’ hybrid lines showed that salt gland density was a highly heritable trait in the salt-treated population. Ultrastructural modifications in the salt glands observed with Transmission Electron Microscopy (TEM), coupled with Cl- localization studies, suggested a preference for symplastic transport of saline ions in Z. matrella. Salt glands have been studied in several plant species; however, no studies have tried to associate the role of ion transporters with the functioning of salt glands in plants. RNA in situ studies with Na+ transporters showed localization of ZmatHKT1 transcripts in the adaxial salt glands, leaf mesophyll and bundle sheath cells for both cultivars. ZmatSOS1 expression was observed in the xylem parenchyma cells for leaves from both cultivars, but the expression was markedly different around the cells bordering the vascular tissue. The strongest expression of ZmatSOS1 for ‘Diamond’ was seen in the bundle sheath cells and the phloem, while for ‘Cavalier’ the signal was strongest in the mestome sheath cells and in cells surrounding the phloem. No expression of ZmatSOS1 was seen in the salt glands for either cultivars. ZmatNHX1 expression in both cultivars was very low, and observed in the salt glands and neighboring epidermal cells. Three alleles of ZmatNHX1 were identified in Z. matrella, along with three alternatively-spliced forms of ZmatNHX1, the expression of which were cultivar and treatment specific. Together, these results provide a model for salt transport in Z. matrella and signify potential roles of salt glands and select ion transporters in the salt tolerance of this species.

This study provides information on the rates of DNA synthesis, sites of DNA synthesis, and DNA content of the avian salt gland during the osmoticstressing (plasma membrane synthesis) and destressing (plasma membrane turnover) cycle, in an effort to better understand the relationship of cell turnover to the initial events in plasma membrane amplification, differentiation, and turnover. The rate of DNA synthesis increases 12-24 h after the onset of osmotic stress, is maximal at about 24 h of osmotic stress, and decreases thereafter in fully stressed and destressed glands. The maximum DNA and protein content, and the maximum protein/DNA ratio are obtained after about 3 days of stress. Autoradiograms show that at 24 h of stress 70-80% of DNA synthesis occurs in connective tissue cells and 20-30% in parenchymal cells, but by 6 days of stress, synthesis occurs about equally in these cell groups. Because destressing is characterized by a large decrease in plasma membrane and in glandular protein, but by little DNA turnover or loss, the loss of plasma membrane is likely due to some type of cell dedifferentiation rather than cell turnover.

Vascular corrosion casting has been used for about 40 years to produce replicas of normal and abnormal vasculature and microvasculature of various tissues and organs that could be viewed at the ultrastructural level. In combination with scanning electron microscopy (SEM), the primary application of corrosion casting has been to describe the morphology and anatomical distribution of blood vessels in these tissues. However, such replicas should also contain quantitative information about that vasculature. This report summarizes some simple quantitative applications of vascular corrosion casting. Casts were prepared by infusing Mercox resin or diluted Mercox resin into the vasculature. Surrounding tissues were removed with KOH, hot water, and formic acid, and the resulting dried casts were observed with routine SEM. The orientation, size, and frequency of vascular endothelial cells were determined from endothelial nuclear imprints on various cast surfaces. Vascular volumes of heart, lung, and avian salt gland were calculated using tissue and resin densities, and weights. Changes in vascular volume and functional capillary density in an experimentally induced emphysema model were estimated from confocal images of casts. Clearly, corrosion casts lend themselves to quantitative analysis. However, because blood vessels differ in their compliances, in their responses to the toxicity of casting resins, and in their response to varying conditions of corrosion casting procedures, it is prudent to use care in interpreting this quantitative data. Some of the applications and limitations of quantitative methodology with corrosion casts are reviewed here.