1. Armstrong CL, Green CE (1985) Establishment and maintenance of friable embryogenic maize callus and the involvement of L-proline. Planta 164: 207–214
2. Barckhausen R (1978) Ultrastructural changes in wounded plant storage tissue cells. In: Kahl G (ed) Biochemistry of wounded plant tissues. De Gruyter, Berlin, pp 1–42
3. Barnabas B, Fransz PF, Schel JHN (1987) Ultrastructural studies on pollen embryogenesis in maize (Zea mays L). Plant Cell Rep 6: 212–215
4. Botti C., Vasil IK (1983) Plant regeneration by somatic embryogenesis from parts of cultured mature embryos of Pennisetum americanum (L.) K. Schum. Z Pflanzenphysiol 111: 319–325
5. Bregitzer P, Somers DA, Rines HW (1989) Development and characterization of friable, embryogenic oat callus. Crop Sci 29: 798–803