Seasonal Cambial Activity and Formation of Secondary Phloem and Xylem in White Oaks (Quercus alba L.)

(1) Background: the cambium has seasonal activity, forming earlywood and early phloem with relatively wide conducting cells, which will function during most favorable season, latewood late narrower typically less season. However, few studies have focused on when these two contrasting tissue types are formed in relation to climatic conditions. (2) Methods: senior author of this paper made weekly collections for an entire year four specimens per collection back 1960s, using traditional anatomical methods study detail what was producing progressively. (3) Results: annual growth rings evident both secondary xylem phloem. The resumes activity April, simultaneous formation wood Both production initiated June, peak ends its August. Phloem marked by radially narrow sieve elements interspersed among a band axial parenchyma dark contents. Most produce only one fiber This feature may be used as indirect ring marker. Wood very vessels thick-walled, fibers. (4) Conclusions: trees their long before beginning autumn, indicating that they prepare ahead selective regime, phenomenon likely dependent photoperiod. Living present yearlong.