The Influence of Proline on the Expansion Potential of Isolated Rye Protoplasts
LIU You-Liang(Nanjing Agricultural University, Nanjing 210014)Steponkus PL(Cornell University, Ithaca, NY 14853 U.S.A.)
The tolerable surface area increment (TSAI_(50)) of protoplasts isolated from nonacclimated leaves of Secale cereale cv. Puma and suspended in sorbitol or NaCl+CaCl_2 solutions was about 1000 μm~2, and was independent of the extent of contraction of the protoplasts. However, when the protoplasts were suspended in proline solution, the TSAI_(50) changed with the contraction. When the protoplasts from isotonic proline solutions expanded in hypotonic solutions, the TSAI_(50) was approximately 1000 μm~2. However, the protoplasts contracted in 0.83, 1.20 Osm or 2.00sm proline solutions when were placed in bypotonic solutions, the TSAI_(50) increased to 1710±85, 1873±91μm~2 and 2200±283μm~2, respectively. These values approached to these of cold acclimated protoplasts either suspended in hypertonic sorbitol NaCl+CaCl_2 or proline (Table 1). The beneficial effects of proline on non-acclimated protoplasts occurred only during contraction, and had no relation to the solution compositien during expansion (Table 2). The mechanism of cryoprotection by proline was discussed.