Zinc-induced Vacuolation in Root Meristematic Cells of Cereals

In the absence of Zn, vacuolar volume fractions of root meristematiccells of Secale cereale L. cv. K2, Triticum aestivum L. cv.Chinese Spring and Oryza sativa L. cv. IR34 were 5.64 x 10^–2,2.17 x 10^–2 and 1.63 x 10^–2 µm³ vacuole µm^–3tissue, respectively. A 4-d exposure to a subtoxic concentrationof zine (0.2 µg Zn cm^–3) induced a 2.93-fold anda 6.78-fold increase in the total vacuolar volume fraction inOryza and Triticum, respectively, whereas no significant increasewas observed for Secale. It is proposed that this Zn-inducedvacuolation represents a compartmentalization mechanism. Theinitial total vacuolar volume fraction in Secale was greaterthan that for Oryza and Triticum and this may enable compartmentalizationof the metal soon after the onset of treatment so reducing itscytotoxic effects. These findings are similar to those observedin contrasting cultivars of Festuca rubra L. Triticum aestivum L, Secale cereale L, Oryza sativa L, zinc, root meristem, vacuolation     

Changes in Cell Number and Cell Division Activity during Endosperm Development in Allohexaploid Wheat, Triticum aestivum L.

Nuclear or cell number, and the mitotic index, were recordedin endosperms of Triticum aestivum cv. Mardler to test if aparticular stage of endosperm development was critical in determiningthe final grain weight. The basal four florets of emasculatedspikelets (controls), and the third and fourth florets of spikeletswhere the two basal ovaries were removed (ovary-removed), weresampled at various times up to 360 h after hand-pollination.The coenocytic phase in endosperms ended about 84 h after pollinationregardless of both grain position and the treatment. The onsetof the cellular stage was characterized by the final large fluctuationsin the mitotic index reflecting the culmination of the synchronousnuclear division of the coenocytic stage. Thereafter, the mitoticindex fluctuated with smaller amplitudes and, by 216 h afterpollination, was < 1%. Neither floret position in the spikeletnor the treatment affected the pattern of alteration to themitotic index. However, ovary removal from first and secondflorets resulted in significantly heavier grains and higherendosperm cell number in the 3rd and 4th florets compared withthe controls. In all florets, mean endosperm cell number peakedat 280 h but decreased by 360 h after pollination. At this time,the mean cell numbers in endosperms of the 3rd and 4th floretsof ovary-removed spikelets were significantly higher than inthe corresponding endosperms in the controls. Thus, a key contributoryfactor in determining the final endosperm cell number may bethe number of cells which are lost during the late period ofthe cellular stage of endosperm development. Key words: Endosperm cell number, florets, grain weight, mitotic index, Triticum aestivum     

Some Cytological Changes accompanying the Regeneration of Meristematic Activity at the Apex of Decapitated Roots of Vicia faba L.

The changes that took place in mitotic index (MI), labellingindex (LI) and the relative proportions of interphase nucleiwith different amounts of DNA have been investigated duringthe regeneration of meristematic activity at the apex of rootsof Vicia faba over the 144 h period following removal of thecap and apical mm of the meristem. Measurements were also madeof the corresponding changes that took place as cells were displacedbasally along the root from the apex over the experimental period.In both parts of the root, MI and the relative proportions ofnuclei with different DNA contents changed from levels similarto those at the apex of the controls at the start and end ofthe experiment to levels resembling those found in more matureparts of the root at 24 and 48 h. In contrast to these results,LI declined over the experimental period. These cytologicalchanges were aresult of the development of lateral root primordiain both the apical 2 mm of the decapitated roots and as cellswere displaced out of the meristem into more basal parts ofthe root. It was concluded that the events leading to the regenerationof meristematic activity at the apex of roots from which thecap and apical mm of the meristem were removed, are no differentfrom those which result in lateral formation as cells are displacedbasally along the primary root from the apex, and they takeplace over the same time interval in both systems.     

Dorisiella arizonensis n.sp., a Coccidium from the Desert Woodrat, Neotoma lepida

SUMMARY. Dorisiella arizonensis n. sp. (Sporozoa: Eimeriidae) is described from oocysts in the feces of a desert woodrat, Neotoma lepida , from Grand Canyon National Park, Arizona. The oocysts are spherical to subspherical, measure 20.8–21.8 × 20.8–22.9 μ, with a mean of 21.0 × 21.8 μ, and have a two-layered wall. They contain 1 to 3 refractile granules but no residual body. The two lemon-shaped sporocysts have a Stieda body, 8 sporozoites, and a few to many scattered, round, clear residual granules or bodies.     

Changes in the Pattern of Cell Division in the Shoot and Root Meristems of Lolium perenne during the Transition from Vegetative to Floral Growth

For Lolium perenne cv. Cropper, a system which resulted in 100%flowering comprised 90 short days (SD) at 4 ?C (vernalization)and 30 SD at 18 ?C followed by 8 long days (LD). The mitoticindex and G1 and G2 percentages were measured in the shoot androot apices of plants following 2, 5 or 8 LD and in SD controlssampled at the beginning and end of induction. Identical measurementswere made in plants given 48 SD at 18 ?C followed by 2, 5 or8 LD; plants remained vegetative in response to this treatmentlacking vernalization. Significant increases in both mitoticindex and meristem size occurred in the shoot apex in LD followingthe vernalizing, but not the non-vernalizing, treatment. A clusterof mitoses in the apical dome of the shoot apex was unique tothe vernalized plants given 5 or 8 LD. However, an increasein root meristem size occurred regardless of vernalization,but a significant increase in the mitotic index was limitedto vernalized plants given 5 or 8 LD. Whilst the vernalization-LDtreatment resulted in an increase in the G2 percentage in theshoot apex following 2, 5 or 8 LD, no such alteration was observedin the root meristem. Thus, the changes to the cell cycle whichcorrelated with flowering were increased mitotic indices andG2 percentages in the shoot apex at each sampling time and increasedmitotic indices in the root apex following 5 and 8 LD. Key words: Cell division, flowering, Lolium perenne L.     

Psychosocial Homeostasis and Jen: Conceptual Tools for Advancing Psychological Anthropology

Personality is a Western concept rooted in individualism. The basic importance accorded it in psychological anthropology has obscured our understanding of how Western man lives in Western society and culture, or how any man lives in any society and culture. What is missing is the central ingredient in the human mode of existence: man's relationship with his fellow men. The concepts of psychosocial homeostasis and jen are designed to extricate our subdiscipline from this intellectual prison. The first describes the process whereby every human individual tends to seek certain kinds of affective involvement with some of his fellow humans. The second refers to the internal and external limits of the individual's affective involvement. With the aid of five major hypotheses based on these concepts, a review is made in a new light of familiar facts drawn from China, the United States, and Japan.