The available data concerning the differentiation of the pericycle in the primary root of Pisum sativum, variety ‘Alaska’, may be summarized as follows. The root tips 3 to 4 day old seedlings germinated in a darkroom at 24°C were fixed with Lillie's buffered neutral formalin. By applying a combination of Lillie's formalin fixation together with methyl blue and/or Heidenkain's hematoxylin and sofranin, the initial symptom of triarch xylary procambium appeared in a procambial cylinder in transverse section of 250μm from the apical initials. Deeply stainable protoplasts of several layer of the pericyclic cells which were localized outside of the xylary procambium show a separation from the thin cell wall. The author would like to designate as ‘α-cells’ these stainable pericyclic cells. The α-cells were localized in the area 250μm to 2150μm from the apical initials. Three to six pericyclic cells in which the protoplasm scarcely stained with the dye solution should be designated as ‘β-cells’. The triarch β-cell zone was localized in a limited area, 550μm to 1750μm from the apical initials. Two or three sieve elements were observable inside of the β-cells. And then, small spherical granules take a deep blue stain in the cytoplasm of the β-cells. It is of paramount importance to determine the chemical nature of the granules. The root tip of Vicia faba L. from 4 to 5 days old seedling germinated in the soil were fixed in Lillie's buffered neutral formalin and stained with 0.5 percent methyl blue. Tetrarch xylary procambium was clearly visible in the transverse sections between 300μm to 550μm from the apical initials. At 1150μm from the apical initials, xylary procambium and several pericyclic cells wear deeply stained. The deeply stained pericyclic cells are designated as ‘α-cells’. In the diurnal condition (11 to 12 AM), normal protoplasts of the α-cells were observable; in the nocturnal condition (11 to 12 PM), the protoplasts of the α-cells showed a contraction. Six to eight pericyclic cells in which the protoplasm searcely stained with the dye should be designated as ‘β-cells’. The differentiation of α-cells and β-cells in the pericycle was seen between 700μm to 2300μm from the apical initials. The available information concerning the effects of acetylcholine upon the protoplasts of mung bean (Phaseolus aureus) root tip may be summarized as follows. On the transverse section of the central cylinder of 1000μm from the primary root apex, there are five to eight pericyclic cells in which the protoplast are stained deeply with methyl blue; these cells contracted with 10^-5M and/or 10^-4M Ach. In the same part of the root, there are tree to five pericyclic cells in which protoplasts are barely stained with the same dye; these cells are not contracted by the Ach solution.

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The application of silicon is known to enhance crop tolerance against various environmental stresses. In terms of drought tolerance, however, studies only focusing on the effects of silicon on transpiration are available and thus relationships between silicon and physiological processes relating to crop drought tolerance remain unclear. Recent studies on water uptake and transport in crops revealed that silicon affected these traits and the effects differed among species. Other recent studies have shown relationships between silicon and dehydration tolerance at cell or tissue levels. In this review, we examine recent and past studies on the effects of silicon on crop drought tolerance to discuss whether the utilization of silicon could possibly enhance the drought tolerance of crops.

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Alashan is an arid area in Inner Mongolia, China, and policies and researches to combat desertification are actively conducted by the local authorities. The airplane is used to broadcast the seeds (i.e., air seeding) of arid plants, Artemisia sphaerocephala, Hedysarum scoparium and Calligonum mongolicum, for the revegetation of wide degraded lands. The control of grazing is an important policy to avoid the degradation of lands. The cultivation of and medical plants is expected to be an alternative income source. The specific ecosystems in the alpine area of the Helanshan Mountains are protected as natural sanctuary.

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