406
15.4.2 Seed Production and Conservation of A. angustifolia’s
Recalcitrant Seeds
Seed production of the old plantation of Manuel Belgrano Forest Station was followed by Fassola et al. (1999) during 5 years on individual trees and mass plots. In
1993, the plots were between 35 and 40 years old; the basal area and the number of
individuals ranged from 23 to 27 m
2
.ha
−1
and 196 to 433 trees.ha
−1
, respectively.
The participation of female individuals was between 23.1% and 40.8% of the total
stand trees. The fall of female cones began in the first week of April, reaching a
maximum in late May and early June and ending in the first half of August. The
largest seed production was in 1994, when 44.3 kg.ha
−1
were collected, in the oldest
plot with the highest proportion of female trees. Female cone production in individual trees was significantly associated with the size of the mother tree and its
sociological position. The maximum recorded seed production was 1.5 kg for a tree
with 52 cm of DBH. These results showed a consistent lower seed production than
the natural forest located in Cruce Caballero Provincial Park, 50 km to the south,
under the same environmental conditions.
A more recent study compared the seed production between plantations installed
at contrasting sites (Simón et al. 2018). Between 10 and 15 female cones were collected in the old plantations of Manuel Belgrano Forest Station (subtropical climate) and in the already mentioned plantations of 25 de Mayo Forest Station
(temperate climate), and the seeds per cone were counted. The average seed productivity was 10 times higher in the temperate climate site with 104 seeds.cone
−1
, compared to 12 seeds.cone
−1
obtained in the subtropical site. This contrasting seed
productivity should be considered for conservation measures. The conditions prevailing during the postfertilization period also influence the seed productivity. High
temperatures registered from December to April have a positive effect on seed maturation (Anselmini et al. 2006). The maximum temperatures during this period are
lower in the subtropical climate of the Province of Misiones, where A. angustifolia
is naturally distributed, and the number of seeds is lower if compared to what occurs
in the temperate climate of 25 de Mayo (Simón et al. 2018).
When Simón et al. (2018) compared the relationship between pollination and
seed yield, they found significant differences in the productivity of both events with
respect to climatic conditions. In the subtropical climate of San Antonio, the amount
of pollen produced was much lower, as well as the number of seeds, as compared to
records from the temperate climate of 25 de Mayo. The reduced production of seeds
was associated with the low number of pollen grains available to fertilize the ovules
and form seeds; the difference between years for both events was smaller than the
difference between environments (Fig. 15.9).
The recalcitrant character of A. angustifolia seeds is another important aspect for
the conservation and use of this species (Tompsett 1984). Several methodological
studies were performed during the 1990s to find an appropriate protocol to stock its
seeds. The main results indicate the possibility of preserving a good germination
capacity for a period of up to 24 months when the seeds are packaged in flexible
plastic bags made with ethyl vinyl acetate and stocked at 0 °C (Chaves et al. 1999;
M. E. Gauchat et al.
15.4.2 Seed Production and Conservation of A. angustifolia’s
Recalcitrant Seeds
Seed production of the old plantation of Manuel Belgrano Forest Station was followed by Fassola et al. (1999) during 5 years on individual trees and mass plots. In
1993, the plots were between 35 and 40 years old; the basal area and the number of
individuals ranged from 23 to 27 m
2
.ha
−1
and 196 to 433 trees.ha
−1
, respectively.
The participation of female individuals was between 23.1% and 40.8% of the total
stand trees. The fall of female cones began in the first week of April, reaching a
maximum in late May and early June and ending in the first half of August. The
largest seed production was in 1994, when 44.3 kg.ha
−1
were collected, in the oldest
plot with the highest proportion of female trees. Female cone production in individual trees was significantly associated with the size of the mother tree and its
sociological position. The maximum recorded seed production was 1.5 kg for a tree
with 52 cm of DBH. These results showed a consistent lower seed production than
the natural forest located in Cruce Caballero Provincial Park, 50 km to the south,
under the same environmental conditions.
A more recent study compared the seed production between plantations installed
at contrasting sites (Simón et al. 2018). Between 10 and 15 female cones were collected in the old plantations of Manuel Belgrano Forest Station (subtropical climate) and in the already mentioned plantations of 25 de Mayo Forest Station
(temperate climate), and the seeds per cone were counted. The average seed productivity was 10 times higher in the temperate climate site with 104 seeds.cone
−1
, compared to 12 seeds.cone
−1
obtained in the subtropical site. This contrasting seed
productivity should be considered for conservation measures. The conditions prevailing during the postfertilization period also influence the seed productivity. High
temperatures registered from December to April have a positive effect on seed maturation (Anselmini et al. 2006). The maximum temperatures during this period are
lower in the subtropical climate of the Province of Misiones, where A. angustifolia
is naturally distributed, and the number of seeds is lower if compared to what occurs
in the temperate climate of 25 de Mayo (Simón et al. 2018).
When Simón et al. (2018) compared the relationship between pollination and
seed yield, they found significant differences in the productivity of both events with
respect to climatic conditions. In the subtropical climate of San Antonio, the amount
of pollen produced was much lower, as well as the number of seeds, as compared to
records from the temperate climate of 25 de Mayo. The reduced production of seeds
was associated with the low number of pollen grains available to fertilize the ovules
and form seeds; the difference between years for both events was smaller than the
difference between environments (Fig. 15.9).
The recalcitrant character of A. angustifolia seeds is another important aspect for
the conservation and use of this species (Tompsett 1984). Several methodological
studies were performed during the 1990s to find an appropriate protocol to stock its
seeds. The main results indicate the possibility of preserving a good germination
capacity for a period of up to 24 months when the seeds are packaged in flexible
plastic bags made with ethyl vinyl acetate and stocked at 0 °C (Chaves et al. 1999;
M. E. Gauchat et al.