After 64 days of aseptic culture, germlings of Pinus Syvestris L. were cut at the middle of the hypocotyl and above the root. The upper and lower halves of the hypocotyls were transferred onto agar medium RM-196 of Linsmaier & Skoog (1964) including 2 mg/l IAA and 0.1, 1 or 10 mg/l kinetin, one or both halves being put in each vial. Callus growth and root formation was observed after 55 days.
The lower ends of basally cut seedlings generally formed callus tissue and 20% of them also formed roots from this callus. No roots and less callus growth were observed in the lower hypocotyle halves excised at both ends. In the latter hypocotyles callus growth was promoted by the presence in the same vial of a basally excised germling, including cotyledons and plumule. Increasing amounts of kinetin slightly enhanced callus formation of basally excised germlings but seemed to inhibit callus growth in hypocotyls excised at both ends and placed alone on the growth medium. The total amount of callus was greatest in hypocotyls which included intact cotyledons and plumule.
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