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Old 12-05-2018, 01:27 PM
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Quote:
Originally Posted by n2ishun View Post
I don't have any solid science to back this up, but in my experience sativa' have small seeds and indica has the larger.
I've grown thousands (very conservatively) of each and from what I've seen you can gauge plant final size by the size of the seed. Small seed = huge plant, huge seed = small plant.

SEED ECOLOGY

Cannabis sativa reproduces by small, slightly flattened one-seeded fruits (classified as achenes), usually referred to as “seeds.” Haney and Kutscheid (1975) stated, “Seed production data probably provide the greatest insight to the ecology of hemp.” Wild (ruderal or weedy) hemp, almost everywhere it occurs, was derived from plants that escaped from cultivation in the past, and reevolved characteristics suited to wild existence. As detailed in the following, the seeds of wild C. sativa are remarkably suited to survival in nature by means of a number of adaptations. Wild populations that have been free from the selective influences of cultivation for many generations manifest extreme development of these adaptations, and conversely, populations only recently escaped from cultivation show only weak or no development of these features.


APPEARANCE

The seeds (achenes) of wild plants have morphological features that easily distinguish them from the seeds of plants that are cultivated, either for fiber, oilseed, or illicit drugs (Small 1975a; Figures 3.3 through 3.5). These features, discussed in the following, are clearly adaptive.


SIZE

In nature, all plants arrive at a compromise between the number of seeds produced and their size.
Like humans, some plants put considerable energy into generating a small number of progeny, which they very carefully nurture. Very large, one-seeded fruits like coconut, which provide a huge amount of “milk” for the embro, exemplify this. More typically, plants produce a very large number of quite small seeds in the expectation that only a few will find suitable habitats and escape destruction. Dandelions exemplify the extreme of producing a huge number of tiny seeds. Cannabis sativa is intermediate in producing a medium number of moderately sized seeds, by plant standards. The species has adopted a strategy that allows small plants to produce at least some seeds, and larger plants to produce many seeds.
The seeds of wild plants of C. sativa are smaller than those of domesticated plants (Figure 3.3).
Seed weight in C. sativa varies enormously, from more than 1000 seeds to the gram in some wild Asian plants to less than 15 seeds to the gram for some cultivated plants (Vavilov 1926b; Watson and Clarke 1997). Usually, the seeds of wild strains are smaller than 3.8 mm in length, in contrast to the larger seeds of domesticated selections. The ecology of the species may differ considerably according to the size of the seeds, and this remains to be studied. The smallest seeds occur in ecotypes native to alpine foothills of the Himalayas, possibly an adaptation to surviving at an ecological limit that is so stressful that it permits only a minimal amount of seed reserves to be accumulated before the plants expire. Large size of seeds in domesticated plants is usually the result of selection for a desired product in the seeds (frequently for food), but also, larger seeds provide a greater store of food reserves for successful germination and establishment. As discussed in Chapter 8 dealing with oilseed cannabis, larger seed size of domesticated seeds could be partly due to the practice of deep planting, requiring large vigorous seedlings to be able to grow out of the deep soil.



FIGURE 3.3 Achenes (“seeds”) of C. sativa (areas of attachment to the plant are uppermost). Left side shows two achenes of a domesticated plant, right side shows two achenes of a ruderal plant. The domesticated fruits are larger, lack a camouflagic persistent covering layer derived from the perianth, and lack an elongated attachment base that facilitates disarticulation in the wild form.

FIGURE 3.4 Comparison by light microscope (above) and scanning microscope (below) of attachment area of domesticated achenes (left) and wild (ruderal) achenes (right). In the wild fruits, a well-developed abscission area is present, and a basal “neck” that facilitates disarticulation is evident.



FIGURE 3.5 (a) Light microscope view of perianth (petal tissue) covering seed (achene) of a wild form of C. sativa. Notice that pigmentation (dark areas) is associated principally with vascular (fluid-conducting) tissue. (b) Scanning electron micrograph of perianth-derived achene covering layer; note areas of straight, aligned cells making up vascular tissue, and areas of nonpigmented areas (regions of cells with wavy margins). (c) Scanning electron micrograph of exocarp (fruit wall) of an achene of a wild form, showing portion covered by persistent perianth and areas where this covering has sloughed off. Photos from Small, E., Can. J. Bot., 53, 978–987, 1975.

SEED SHEDDING

In nature, plants reproduce mainly by distributing propagules, mostly seeds and fruits (occasionally vegetative tissues), commonly by wind, water, gravity, and cooperating wild animals.
Humans have domesticated many wild plants, frequently specifically to harvest the seeds or
fruits. Most wild plants cast off their seeds or fruits as soon as they mature, by various mechanisms. This has two undesirable consequences from an agricultural perspective: when a seed or fruit drops away, it is more difficult to collect; and when seeds or fruits do not remain attached to the plant at maturity, it necessitates repeated collection of propagules from each plant over the weeks that they sequentially mature. Selecting mutations that inactivate the separation mechanism (abscission, i.e., breaking away of fruits at their base so they fall away) or the dehiscence mode (i.e., opening of fruits to release seeds) with the result that the mature seeds or fruits remain on the plant greatly facilitates harvest. This reduction of “shattering” (natural shedding of seeds at maturity) is the most important way that humans have domesticated the majority of crops (Harlan 1995; Fuller and Allaby 2009). Cereals currently supply more than half of the calories consumed by humans (Small 2009), and in all of them, a “domesticated syndrome” of characteristics is recognizable whereby the “grains” (fruits technically termed caryopses) have lost the features in their wild ancestors that cause them to detach and scatter away (see, for example, Sakuma et al. 2011).
Although the precise anatomical and morphological features that facilitate release of cereal grains and the seeds of C. sativa differ, one can recognize a syndrome of seed characteristics that differentiate wild C. sativa from domesticated kinds of fiber hemp, oilseed hemp, and marijuana plants. The key feature enabling rapid release of seeds at maturity is the presence of an “abscission zone” (area of weak cells that weaken at maturity) at the base of the seed. At the base of the cannabis seed, one often views a circular scar (sometimes referred to as a “horseshoe” in European literature), the remnants of a plane of weakened tissue that served to disarticulate the seed from the stem to which it was attached. In conjunction with this feature, the base of the seed is often attenuated (elongated and narrowing), a characteristic that assists the seed to fall away easily from surrounding tissues of the infructescence (fruit-bearing portion of the plant). The combination of an attenuated base and a well-developed abscission zone in wild seeds (illustrated in Figures 3.3 and 3.4) facilitates disarticulation as soon as the fruits are ripe, and this is essential given the considerable predation by birds on seeds that remain attached to the plant.
In addition to the features described here, humans have selected seed-bearing crops that mature most of their seeds more or less simultaneously, to minimize harvest loss. As well, a highly congested fruit axis (adjacent seeds very close together along with bracts and young leaves) makes it very difficult for seeds to fall away from the plant and facilitates harvest of the seeds. A corn cob illustrates just how close together seeds can be packed and how most of them mature more or less simultaneously. These features are evident in plants selected for yield of seeds (as described in Chapter 8). By contrast, wild C. sativa plants mature seeds sequentially over a long season, and the seeds are relatively well separated so that they do not interfere with each other’s ability to fall off the plant.


PROTECTIVE THICK SHELL

In contrast to domesticated seeds, wild seeds have a comparatively thick fruit wall or “hull.” This (1) protects the seeds against mechanical abrasion; (2) makes it more difficult for herbivores to break open the seeds and consume the embryos; (3) makes it more difficult for water to penetrate, so that
the seeds won’t germinate and will remain dormant, providing for germination over several years; and (4) keeps oxygen from entering and degrading the storage oil. Possibly, the thick shell also serves to protect the seeds from being digested while they are in the gut of some animals, so that they will be deposited and germinate in the animal’s excrement, an environment to which cannabis is adapted.


CAMOUFLAGE

A camouflagic mottled layer covers the seeds of wild C. sativa, providing some protection for the fallen seeds against mammalian and insect herbivores. The layer is developmentally homologous with the perianth—the petals and sepals of many flowers. The dark appearance of wild seeds also contributes to their being inconspicuous. By contrast, as discussed in Chapter 8 dealing with oilseed cannabis, light-colored seeds have often been selected in cultivated plants.


"Cannabis A Complete Guide"
Ernest Small
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Last edited by Efesto; 12-05-2018 at 11:34 PM.
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  #62  
Old 12-05-2018, 04:05 PM
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This was a very interesting read, thanks for sharing.
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  #63  
Old 12-08-2018, 05:47 PM
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Nice read^^

I've been chewing away at this interesting read about landraces and population breeding...

http://sharebooks.com/system/files/R...Resistance.pdf

http://sharebooks.com/content/plant-...raoul-robinson
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  #64  
Old 12-08-2018, 10:21 PM
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the complete book can be found on Library Genesis: Library Genesis or http://93.174.95.27
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  #65  
Old 12-09-2018, 03:36 PM
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Default WEED 1971

https://youtu.be/v1x827YtSJw
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