71
3.5 Domestication of Raulí: A Potentiality
with a Long History
The availability of seeds constitutes a bottleneck for the production of raulí seedlings and may become a problem for the massive production of plants for commercial purposes. Until present, all seeds utilized come from natural forests, where a
considerable annual variation in seed production was observed at every stand, with
mast years and years of virtually zero production, in cycles of unpredictable duration yet. A marked variation among stands for the same year also occurs (Marchelli
and Gallo 1999), and even genetic diversity significantly varied in the same population between good and bad seed-producing years (Marchelli 2002).
Moreover, not only productivity seems to vary from site to site and year to year
but also the percentage of empty seeds. The genus is capable of developing fruits
through parthenogenesis, that is, without fertilized ovules mediation (Poole 1951).
This happens every year in a very high proportion but with temporal and spatial
variation. In a single-year collection of seeds in eight Argentinean populations,
Barbero (2014) measured mean values of empty seeds per population ranging from
38% to 79%, with individuals producing only empty seeds. This author also showed
that the proportion of filled seeds was higher in those of flat shape than in the triquetrous ones (Fig. 3.6). Just as the collection of seeds in nature can be a bottleneck, it
was also observed (at least preliminary) that plantations with direct insolation begin
to produce seeds after 12 years, reaching regular production almost every year at
age 15, with a low relative proportion of empty seeds. These observations encourage the establishment of seed orchards.
Viable seeds are needed to produce seedlings at industrial scale, but also the
knowledge to manage the natural process of germination is necessary. Because seed
germination is probably the most important decision in plant life history, it is
strongly environmentally regulated. This regulation provides advantages to the
organism because it restricts seedling emergence to the conditions that are likely to
be favourable for the success of the new individual, promoting fitness. However, the
existence of specific requirements for germination may constitute a problem and a
real bottleneck for the massive production of plants for commercial purposes.
The regulation of germination by environmental cues is usually related to the
existence of seed dormancy, i.e. when a viable seed is not able to germinate even
when exposed to favourable conditions of water, concentration of gases and temperature (Bewley et al. 2013). In several species, seeds use to be highly dormant at
the moment of dispersal, and dormancy is alleviated in a process defined as afterripening, which is expressed by an increment in the permissive ranges of environmental conditions in which germination occurs (Batlla and Benech-Arnold 2015).
Temperature is one of the main environmental factors that regulate seed behaviour of N. alpina seeds, having major effects both in dormancy and in the rate of
germination of non-dormant seeds. The use of thermal time models provides a conceptual framework for distinguishing these two effects of temperature on seed
behaviour (Batlla and Benech-Arnold 2015) and establishes that a certain quantity
3 Raulí (Nothofagus alpina = N. nervosa): The Best Quality Hardwood in Patagonia
3.5 Domestication of Raulí: A Potentiality
with a Long History
The availability of seeds constitutes a bottleneck for the production of raulí seedlings and may become a problem for the massive production of plants for commercial purposes. Until present, all seeds utilized come from natural forests, where a
considerable annual variation in seed production was observed at every stand, with
mast years and years of virtually zero production, in cycles of unpredictable duration yet. A marked variation among stands for the same year also occurs (Marchelli
and Gallo 1999), and even genetic diversity significantly varied in the same population between good and bad seed-producing years (Marchelli 2002).
Moreover, not only productivity seems to vary from site to site and year to year
but also the percentage of empty seeds. The genus is capable of developing fruits
through parthenogenesis, that is, without fertilized ovules mediation (Poole 1951).
This happens every year in a very high proportion but with temporal and spatial
variation. In a single-year collection of seeds in eight Argentinean populations,
Barbero (2014) measured mean values of empty seeds per population ranging from
38% to 79%, with individuals producing only empty seeds. This author also showed
that the proportion of filled seeds was higher in those of flat shape than in the triquetrous ones (Fig. 3.6). Just as the collection of seeds in nature can be a bottleneck, it
was also observed (at least preliminary) that plantations with direct insolation begin
to produce seeds after 12 years, reaching regular production almost every year at
age 15, with a low relative proportion of empty seeds. These observations encourage the establishment of seed orchards.
Viable seeds are needed to produce seedlings at industrial scale, but also the
knowledge to manage the natural process of germination is necessary. Because seed
germination is probably the most important decision in plant life history, it is
strongly environmentally regulated. This regulation provides advantages to the
organism because it restricts seedling emergence to the conditions that are likely to
be favourable for the success of the new individual, promoting fitness. However, the
existence of specific requirements for germination may constitute a problem and a
real bottleneck for the massive production of plants for commercial purposes.
The regulation of germination by environmental cues is usually related to the
existence of seed dormancy, i.e. when a viable seed is not able to germinate even
when exposed to favourable conditions of water, concentration of gases and temperature (Bewley et al. 2013). In several species, seeds use to be highly dormant at
the moment of dispersal, and dormancy is alleviated in a process defined as afterripening, which is expressed by an increment in the permissive ranges of environmental conditions in which germination occurs (Batlla and Benech-Arnold 2015).
Temperature is one of the main environmental factors that regulate seed behaviour of N. alpina seeds, having major effects both in dormancy and in the rate of
germination of non-dormant seeds. The use of thermal time models provides a conceptual framework for distinguishing these two effects of temperature on seed
behaviour (Batlla and Benech-Arnold 2015) and establishes that a certain quantity
3 Raulí (Nothofagus alpina = N. nervosa): The Best Quality Hardwood in Patagonia