Presentation on theme: "Relationship between cone weight and seeds traits as revealed by several years study on Cedrus atlantica individuals at Tala-guilef (Djurdjura, Algeria)."— Presentation transcript:
Relationship between cone weight and seeds traits as revealed by several years study on Cedrus atlantica individuals at Tala-guilef (Djurdjura, Algeria). F. KROUCHI and A. DERRIDJ Laboratory of Forest Biosystematics Faculty of Biological and Agronomic Sciences Mouloud Mammeri University (Tizi-Ouzou, Algeria).
Material and methods Isolated trees were sampled in two adjacent stands: Each tree was permanently identified. Cones were collected during 05 years : 1992-93-98-99 and 2001. Trees concerned each year depended on cone availability and crown access.
Partial view of the stand 1. Partial view of the stand 2
The following parameters were studied on each cone : + Cone weight ; + Total number of seeds ; + Amount of well developed (i.e. filled) seeds ; + Weight of 10 seed lots ; + Germination rate ; + Germination mean time.
Results Category of seeds extracted from cones: a-Well developed seeds (found at the central part of the cone) subdivided to : a-1- filled seeds ; a-2- empty seeds ; a-3- seeds attacked by insects (Megastigmus suspectus var. pinsapini) b- flattened seeds with integument but without embryo and endosperm (found at the central part part of the cone); c- wings with a small lignified feature (found at the basal part of the cone). The amount of filled seeds decrease mainly due to the flattened seeds while empty seeds and parasitised ones are present at low frequencies.
Categories of seeds found in a cone A: seeds of normal dimension (filled, parasitised or empty) B1: flattened seeds; B2 and B3: wings with a lignified feature
Level of inter-individual variation in cone traits. + A mosaic of variation was observed between trees in a stand for the whole cone traits. + On isolated trees cone traits did not differ with branch exposition while cones of shaded branches are smaller than those of exposed branches of the same tree. + Mast years as well as bad fruiting ones are synchronized over stands and trees. + Through the 5 years of investigation, year 2001 showed a combination between a low cone crop and low amounts of filled seeds per cone.
Relationship between parameters: + The amount of filled seeds is negatively correlated to the amount of flattened seeds which are assumed to result from lack of pollination; + Heavy cones bear heavy seeds but may not necessarily bear high amounts of filled seeds; + Cone weight and seed weight are not good predictors of seed germination capacities; + During cone collection, we must not relay on cone dimension as a good predictor of the number of filled seeds; + High numbers of seeds/cone do not necessarily result in high amounts of filled seeds; + Cone traits are not correlated to cone crop size and to tree diameter.
Conclusion A mosaic of inter- individual variation was revealed for cone and seeds traits on a small scale. A year effect is also significant on these traits (data not shown). It should be better to collecte cones in mast fruiting years in order to obtain high amount of filled seeds.