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Changes induced by culture solution salinity to the anatomy of roots of trifoliate orange grafted with Satsuma Mandarin [Japan]  [1999]

Mohammad, P. (United Graduate School of Agricultural Sciences, Matsuyama (Japan). Faculty of Agriculture) Shiraishi, M. Ono, H.

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Anatomical changes in root tips of trifoliate orange grafted with satsuma mandarin (Citrus unshiu Marc. cv. Okitsu Wase) at 0, 10, 25 and 50 mM NaCl in the culture solution were investigated after 3, 5, 8, and 10 days induction. At no-salt-control treatment, the root tips were always sharply pointed, apical initial cell layers were distinct and meristematic zone was wider. The rootcap and cortical cells apart from the root tip possessed only a few starch grains. The cortical cells were elongated and cell length gradually increased from the root tip towards the base. In contrast, under 10 mM NaCl, root tips gradually turned round and the meristematic zone finally shortened. Only a few starch grains accumulated up to 8 days of induction followed by degradation in the rootcap cells but cortical grains gradually increased. At 25 mM NaCl, severe sloughing of rootcap cells and the secretion of mucilaginous substances appeared on the 5th day. The epidermal and root tip injuries were found and the apical initial cell layers became indistinct from the 5th day onward. Lignification occurred in the central cylinder which gradually proceeded towards the root tip. Starch grain accumulation increased in the cortical cells but decreased in the rootcap cells along the exposure time to the saline solutions. The cortical cells tended to round and cell length increased near the root tip. At 50 mM NaCl solution, root tip and epidermal injuries and lignification in the central
cylinder initiated on the 3rd day and became severe at longer exposure. Starch grains were not found in the rootcap cells but the cortical grains gradually increased. The cortical cell rounding and enlargement started from the very beginning of induction.