CHANGES IN CARBOHYDRATE AND NITROGEN RELATIONSHIPS DURING EPISODIC GROWTH OF LIGUSTRUM-JAPONICUM THUNB

Rooted cuttings of Ligustrum japonicum Thunb., an episodically growing species, were-grown hydroponically in a controlIed-environment growth chamber to determine allocation of glucose, mannitol, total soluble s ugars, and total protein in mature leaves, flush leaves, stems, and ro ots, During the 65 days of episodic growth, 43% of the total soluble s ugars was glucose and 33% mannitol. Glucose concentrations of mature l eaves decreased during the first root growth episode, increased in alm ost all plant tissue during a shoot growth episode and decreased in al l plant tissue at initiation of a second root growth episode. Mannitol concentrations in the roots and stems decreased during episodes of ro ot growth and increased during a shoot growth episode when leaf flush mannitol concentrations increased. Radiolabeled C applied to leaves be fore thr initiation of the first period of shoot elongation was transl ocated to the roots. After shoot elongation, just before a root growth episode, most labeled C was translocated to new shoots and roots, Aut oradiographs indicated that subsequent episodes of shoot growth were s upported by photosynthate from the previous shoot flush, Protein conce ntrations decreased in all plant tissues during shoot growth but incre ased in roots and mature leaves during root growth. Concentrations of N-15 in leaf and stem tissue indicated retranslocated N supported each episode of shoot growth. Changes in endogenous and N concentrations a nd allocation patterns in ligustrum were linked to the control of epis odic shoot and root growth.