X-RAY MICROSCOPY 



method is still in process of in sections as thick as 80 n, give statistical 

 development at the present time, information of which other techniques are 

 Besides the plant tissue artefacts men- incapable. MR is able to distinguish two 

 tioned above, artefacts inherent in these (or several) groups of substances both hire- 

 optical methods lower the quality of fringent, in cases where they show different 

 radiograms if they are not corrected. x-ray absorption (by example lignin from 

 Results drawn from medical or animal calcium oxalate crystals). Other results in 

 investigations can incite plant cell research plant field show great utility of MR in path- 

 to intensive application. It is known, among ologic and trophic problems: this method 

 other examples, how mineral elements are discloses high absorption of tumoral meatus 

 distributed in calcified bone tissue, how though these are not birefringent in polarized 

 lipids, pentose-nucleoproteins and proteins light, mineral matter being in an unusual 

 in nerve cells are quantitatively determined amorphous state in them. As MR provides 

 by x-rays. Perhaps most botanists ignore information on motion of heavy ions during 

 still these possibilities and also the limita- nuclear division, it serves in the same way 

 tions of microradiographic techniques. for a cell such as pollen and for tissue either 

 The role of microradiography is primarily normal or tumoral such as stem. Leaves fed 

 to detect or localize opaque substances, with different nutrients have been distin- 

 However it does not always take the place guished only by MR. 



of other techniques. If MR is able to be a If we compare now MR and electron 



worthy auxiliary method in botanical re- microscopy, both evidently apply to two 



search, it would be inadvisable to neglect different scales of magnitude. The latter 



information obtained by other methods such concerns purely descriptive cell morphology 



as crystallography, histology, cytology or with a resolving power of the order of a few 



microchemistry. Surely it is expedient to A, but it is closely dependent on the kind 



know the very interesting attempts to ob- of fixation. MR is on a microscopic scale of 



tain precise knowledge of living matter by complementary interest to the use of the 



x-ray techniques, as did Zeitz and Baez (23) ordinary optical microscope because the 



on Mn and Rb content of tea leaves; their resolving powers of both are similar. Thus 



physical work is necessary to future progress they contribute together in the solution 



in microanalysis. But a botanist knows that of the same problems in the plant field. 



spots in leaves generally are calcium salts Some typical examples are illustrated in 



and they will have to inquire with a crystal- the figures, each of which is described in a 



lographic method as to precisely what kind specific legend, 

 of salt composes the crystals of spots. Mi- 



, . , ,, -J • r i- REFERENCES 



crochemistry usually provides miormation 



about ions present in situ. In this way both I- ^o^^^.^ '^"^ (ieneral Information about Micro- 

 chemical composition and localization will 



be correlated Cosslett, V. E., Microscopy with X-raj^s, Nature, 



On the other hand there are advantages ^ \r t^ t? ■■ x' d 



° Cosslett, V. E., Engstrom, A. and Pattee, 



of microradiography relative to other tech- h. H., X-ray Microscopy and Microradiog- 



niques in some results recently acquired. It raphy, Acad. Press, N. Y., 1957. 



discloses in normal plant tissue interesting Engstrom, A., Biological Ultrastructure, 326 p., 



architectures as crystallized components, Acad. Press, N. \., 1957. 



, ,, a Henke, B. L., High Resolution Microradiography, 



mipregnations, mtra- or extra-cell flow. 



Microradiographs, in which there is a sum- * ggg also other articles on X-Ray Microscopy 



mation of numerous elements of a formation in this Encyclopedia. 



646 



