Optimization of cork oak (Quercus suber) seed storage and its impact on seedling quality

Doutoramento em Engenharia Florestal - Instituto Superior de AgronomiaRapid loss of viability of cork oak (Quercus suber L.) recalcitrant acorns represents one of the limitations to their regeneration. The cold storage procedure (2-4ºC) recommended for extending seed longevity of Quercus genus proved ineffective: the harvest is totally lost within 3 months of storage and the processing costs are very high. The main objective of this study was the optimization of acorns storage for a minimum period of 6 months in order to permanent availability of high quality reproductive materiel and, consequently, to enhance the reforestation success. We performed the acorns storage taking in account the mother-tree and bag type, and assessed their physiological behavior, before and at different times of storage, to understand the biology process and the impact of tree-mother in storing success. In parallel, we assessed the effect of storing on the seedling quality. Then we monitored the acorn maturation to set the right time for harvesting and assessed its initial sanitary quality as well as its effect on the seedling vigor. In order to demonstrate the storage technique and inform against its limitations, we analyzed the acorn quality at two storage levels (5 and 17 months). In the context of implementation of the technique, we assessed the effect of nursery time production (NTP) and fertilization on the seedling growth potential. A new procedure of cork oak acorn wet-cold storage was developed for a period of 12-15 months (12-15MC) and implemented at real scale with developing an efficient prototype of acorn processing. The technologic process was patented® and amend radically the usual seed storage procedure. The effectiveness of long-term storage depends on the maturation control which guarantees the initial acorn quality, on the accuracy and speed of treatments (thermotherapy and drying) and on the storage conditions improvement. The quality of acorn and seedling from this innovation was significantly improved when compared to the usual reproductive material. Hence, germination of stored acorn becomes rapid and uniform and root growth potential (PCR) of subsequent seedling was significantly higher than the conventional seedling and similar to the fertilized one