CAMBIAL ACTIVITY IN EUCALYPTUS CAMALDULENSIS DEHN.

Abstract

SUMMARYThe production of xylem and phloem elements by the cambium of Eucalyptus camaldidensis was investigated. Plants grown under various climatic treatments were exposed to '"""CO, for short periods. This treatment left a marker in the xylem and in the phloem cells derived from the cambium during the exposure. Thus, the newly formed cell layers could be counted. Results reveal that the ratio of the number of xylem layers produced to the number of phloem layers produced (4 : i) is practically independent of many environmental factors. The ratio was also found to he independent of the rate of cell production as well as of the width of the undifFerentiated cambial zone.Changes in the ratio of xylem to phloem were not found in plants treated with naphthalene acetic acid, kinetin or triiodobenzoic acid, nor in plants which were defoliated or disbudded. However, a higher ratio was found for plants treated with gibberellic acid.

Sector analysis reveals patterns of cambium differentiation in poplar stems

“…Typically, during normal stem growth, XMCs are mitotically more active than PMCs, leading to a disproportionate ratio of xylem to phloem elements, although this varies between species and physiological state. In our experiments, we observed an average ratio of four xylem to one phloem derivative which aligns well with observations by Waisel et al (1966) in Eucalyptus camaldulensis who reported that approximately four xylem derivatives were produced for every one phloem derivative regardless of changes in environmental conditions including photoperiod, thermoperiod, and season. In Populus euramericana , Stahel (1968) observed a ratio of 10:1 during normal growth conditions, and Larson (1994) in a review of this subject presented a selection of xylem/phloem ratios from several tree species and found values that ranged between 15:1 and 1:1.…”

The scaling of the hydraulic architecture in poplar leaves

“…The 1 : 10 phloem to xylem ratio across vein orders found for Populus tremula × alba (Fig. ) matches the annual growth ratio reported for other species of Populus (Evert & Kozlowski, ), and falls within the 1 : 4 to 1 : 10 ratio reported for vascular tissue production in other deciduous temperate trees (Artschwager, ; Waisel et al ., ). The similarity among phloem‐to‐xylem ratios in leaf veins and stems might reflect similar behavior in procambium activity within the entire plant body.…”

A Patchy Growth via Successive and Simultaneous Cambia: Key to Success of the Most Widespread Mangrove Species Avicennia marina?

“…A strictly controlled growth layer formation results in a regular dispersion of the phloem tissue over the entire stem disc. Within one growth layer, the ratio of xylem to phloem tissue is lower compared with trees with conventional secondary growth (ratio: 2 -9; Table 3) (Artschwager, 1950;Waisel et al, 1966;Rajput and Rao, 2000). Besides, they accumulate only a limited number of phloem increments, making the total phloem fraction of an Avicennia stem considerably higher (Esau, 1969).…”