Impact of provenance and seed moisture content on seed quality of Chestnut-leaved oak (Quercus castaneifolia C. A. Mey.)

Effects of provenance and seed moisture content (SMC) on viability, germination and vigor of chestnut-leaved oak(Quercus castaneifolia) acorns were investigated in laboratory. For this purpose, 1500 sound and mature acorns were selected from three different provenances in Loveh forest, north eastern of Iran, located in elevations of 400, 1000 and 1600 meter above sea level, with initial moisture content of 47.0%, 43.0% and 42.8%, respectively. In order to set up 5 different SMC levels (including control, 39.4%, 35.1%, 30.1% and 25.9%) in each seed provenance, acorns were dried for 7 days close to silica gel in 27°C. All dried acorns imbibed in tap water for 24h and incubated under optimum growth condition (8h light in 30°C, and 16h dark in 20°C) for 30 days using a complete randomized factorial design, with 4 replications. At the mentioned period, number of germinant, and characteristics of emerged seedlings were recorded every other day. Results showed that acorn quality decreased with seed MC reduction. So that, in all studied provenances, reduction of SMC lead to reduce seed viability, germination percent, germination speed, germination value, germination energy, and vigor index. Accordingly, it can be said that Q. castaneifolia seed apart from provenance has recalcitrant seed storage behavior. In this study, we found that threshold water content (TWC), critical water content (CWC), and lethal water content (LWC) of chestnut-leaved oak seed are %35.5, %30.1 and %24.3, respectively. Incidentally, aforesaid limits changed slightly in different provenances. Totally, in order to retain chestnut-leaved oak seed quality, the results suggest that seed technologists should retain SMC above %35.5 (TWC). Because in lower SMC, seed viability decreases gradually. So that until CWC (%30.1) half of seeds lost their viability. Furthermore, because rehydration of seeds with SMC bellow %24.3 (LWC) can not restore their viability, silviculturists and forest nursery managers should avoid sowing acorns with SMC bellow %24.0