Effects of acorn storage duration and parental tree on emergence and physiological status of Cork oak (Quercus suber L.) seedlings

Abstract

-This study was conducted to evaluate how parental trees and seed storage duration influenced subsequent seedling physiological status and growth. Seedling emergence rate was higher than 90% independently of the duration of seed storage or parental trees. Seed storage shortened significantly the time and increased the uniformity of seedling emergence. Consequently, the delayed seedling emergence from fresh seeds could be explained by epicotyl dormancy. Seed size varied with parental tree. Seedling growth rate was greatly affected by seed size, independently of storage treatment. Seedlings originating from large seeds (>5 g) had the fastest growth rates and seedlings from the smallest seeds (<4 g) had the slowest. Final shoot height, however, depended on the duration of seed storage. The seed size and the duration of storage had a great effect on the initial rate of leaf production, but did not affect the final number of leaves. Leaf chlorophyll concentration was reduced as the duration of seed storage increased but was independent of parental tree (i.e., seed size). Seedling biomass was positively related to seed size. The duration of seed storage reduced the shoot/root ratio, but no significant effect was observed among parental trees. The shoot/root value of seedlings from stored seed was about 1.5 and the one of seedlings from fresh seed was about 2. seed storage / seed size / seedling growth / shoot / root ratio / Quercus suber Résumé -Effet de l'arbre producteur et de la durée de conservation des glands sur l'état physiologique des plants de chêne liège (Quercus suber L.). Quel que soit l'âge des glands ou l'arbre producteur, l'émergence des plants est supérieure à 90 %. La durée et l'uniformité de l'émergence des plants sont significativement affectées par la conservation des glands ; par conséquent le retard dans l'émer-gence des plants issus des glands frais peut être expliqué par l'existence d'une dormance épicotylaire. La croissance des plants est rythmique : elle est caractérisée par une alternance de périodes d'allongement et de périodes de repos. Le rythme de croissance est fortement affecté par la taille des glands quel que soit leur âge. En effet, la croissance des plants issus des gros glands (>5 g) est plus rapide que celles des plants issus des petits glands (<4 g), mais la hauteur finale dépend de l'âge des glands. La taille des glands et leur conservation affectent fortement le rythme d'apparition des feuilles mais pas le nombre final. La concentration en chlorophylle des feuilles diminue chez les plants issus des glands conservés quel que soit l'arbre producteur. La biomasse des différentes parties du plant est réduite pour les petits glands conservés. La conservation des glands influe sur le rapport système aérien/système souterrain, mais aucun effet de l'arbre producteur n'est observé. Sa valeur est de 1,5 pour les plants issus des glands conservés et de 2 pour ceux issus des glands frais.conservation des glands / taille des glands / croissance des plants / rapport système aérien/...

The importance of seed reserves for seedling performance: an integrated approach using morphological, physiological, and stable isotope techniques

“…These similar results are not surprising because the availability of a given resource in the seed is largely a function of the total seed mass (Kitajima and Fenner 2000). The positive correlation between seed size and seedling biomass documented here concurs with the results of numerous studies within the family Fagaceae (Aizen and Woodcock 1996;Kormanik et al 1998;Bonsil 1998;Merouani et al 2001). Furthermore, the seed reserve and seedling biomass relationship we documented is similar to Bonsil (1998), who found that cotyledon excision significantly reduced subsequent seedling growth of both Q. rugosa and Q. laurina.…”

Influence of cotyledon removal on early seedling growth in Quercus robur L.

“…This positive effect of seed size on seedling growth affects not only final seedling size, but also its growth rate as shown in Merouani et al [20]. These authors confirmed that seedlings of Quercus suber originating from the largest seeds had also the fastest growth rate.…”

Consequences of cutting off distal ends of cotyledons of Quercus robur acorns before sowing

“…In many tree species, initial seedling growth is positively correlated with seed mass (Howe and Richter 1982;Vaughton and Ramsey 1998;Sousa et al 2003;Kennedy et al 2004), and this is also true in oak species (Merouani et al 2001;Grossman et al 2003). Furthermore, larger oak acorns have a higher germination rate (Gomez 2004;Tilki 2010).…”