The avocado, female today, male tomorrow

The Avocado, Persea gratissima or Persea americana, is a Central American fruit tree of the Lauraceae family of grown three races: Mexican, Guatemalan and Antillean, with many natural hybrids between them have led multiple varieties. Mexican cultivars generally resist the cold better than the Guatemalan and Antillean. Under optimum growing avocado tree born of seed can exceed 20 meters, being a wild specimen reaches 30 meters. The grafted samples are much lower, which facilitates the collection of fruit. In recent decades, the cultivation of varieties of Mexican race has spread to many countries with subtropical and Mediterranean climate without frost, especially in coastal areas.

The avocado has hermaphrodite flowers that prevent selfing of a very clever way. The flowers open in two phases well separated in time. In the first phase all flowers of same tree open as female pistil receptive to pollen from other trees, but with undeveloped six stamens to pollen can not fertilize at the same pistil. These details are clearly visible in this and the following images. Recommend expanding the photos with a double click.

Avocado flowers are inconspicuous. Lack petals. The sexual organs are surrounded by six sepals yellow-green to a yarn in each of them. To attract pollinating insects have three orange nectaries situated between the stamens and ovary. With the nectar the bees produce a dark honey with a characteristic taste. In plantations of Malaga, Granada and the Canary Islands produce large amounts of avocado honey protected designation of origin.

In this other flower in female phase is clearly visible all the details. In the center is the swollen ovary of the white pistil leaving just the stigma receiving pollen. Surrounding the ovary are the three nectar of a vivid orange, followed by the six stamens in which extreme are full of pollen anthers still immature.

Finishing the day of the first stage of flowering the female stigma is sealed and the male anthers of the stamens begin to mature, so that at sunrise the next day all flowers of same tree enter the male phase of flowering and anther open for insect pollinators are impregnated with the pollen and bring it to the flower of another avocado that day is in female phase. Thus it is almost impossible for the own pollen fertilizes the stigma, thus avoiding inbreeding would lead to the degeneration of the species perpetuating regressive genes.

Here we see three flowers in male phase with mature stamens that have been stretched and lifted so that the insects gluttonous of the nectar are impregnated with the pollen from the anthers.

In some mysterious way which has not yet been explained all individuals of the same cultivar agree to bloom at the same level on alternate days. In large plantations of avocados grow different cultivars are often intermingled, as if they were planted all of the same cultivar bloom all at the same level and no flowers would be pollinated so they would not give any fruit.

In avocado plantations of a single cultivar, to get to fruition, the agriculturists use the random planting of some individuals born seed edges, ie mongrel hybrid, each of which blooms in a different phase, so that ensure good pollination, and that whatever the stage of flowering of avocado plantation edges will always be several avocados flourish in a different phase, bringing the precious pollen by bees and other insects.

In this type of fruit is well understood the importance of bees as pollinators, without which very few flowers would be pollinated and the fruits would be very rare. Pesticide spraying in full bloom would be catastrophic for the bees and productivity of avocados.

Avocado flower in the male phase. The sepals are bent down to make it exposed the stamens and facilitate impregnation with pollen from insects. In this second phase the three nectaries still produce abundant nectar to attract pollinators to flowers.

Another flower of Persea gratissima in male phase. If the ovary is fertilized with pollen from another avocado in a few days begin to grow larger and change its color from white to green. With the passage of the days its weight will double the long petiole downwards and the fruit will acquire the aspect of a testicle. Just the name of avocado, ahuacatl, comes from the ancient Aztec language Nahuatl and means testicle. The word guacamole, ahuacamolli, also comes from the Nahuatl language and means avocado salsa. During the Inca empire avocado cultivation spread south and in Quechua-speaking Incas gave the name of Palta, which is why in South America they call the fruit Palta and the tree Palto.

And here is the result of this curious flowering in two phases, a beautiful ahuacatl or palta seed always a hybrid, which if planted will result in a massive tree that will take about 12 years to give their first flower and 15 years to produce the first fruits, as during the early flowers tend to fall without reaching fruition.

The fruits may be round or oblong, with green or purple skin, smooth or rough and weight can range from about 50 grams in dwarf avocados without seed to more than one kilogram in some varieties of Puerto Rico.

Ceterach lolegnamense, with two mutations it was turned fertil

Ceterach lolegnamense fern, also called Asplenium lolegnamense, is an endemism of Madeira absolutely amazing. For its status of allohexaploid hybrid should be sterile and die without issue but managed to evade his fate and survived by two mutations that laugh at the laws of genetics, Apomeiosis or absence of meiosis in the sporangia, resulting in hexaploid spores perfectly viable and Apogamy or Gametophytic Apomixis allowing it to produce a new fern from a somatic cell of the gametophyte, skipping fertilization because their gametes are not viable.

Ceterach lolegnamense in a very damp and shady wall oriented toward the northwest located on the road to Curral das Freiras. Is rooted on a bed of moss, lichen and Selaginella denticulata, which act like a sponge and keep the soil constantly moist. It is very striking resemblance to its ancestor Ceterach aureum.

Interestingly, despite being endemic to Madeira, its origin seems to be in the nearby Canary Islands. Both parents, the allotetraploid Ceterach aureum (Asplenium aureum) and the allo-octoploid Ceterach octoploideum (Asplenium octoploideum synonymous with Ceterach aureum subsp. Parvifolium) only live in the Canaries. It is assumed that several million years ago, perhaps during the Messinian period of Miocene, the spores were able to get to Madeira, or carried by wind or glued to the feathers and feet of sea birds, capable of germinating on the volcanic lava populate this beautiful Portuguese island. It ignores the reasons for the extinction in the Canary Islands.

In its genome is a curious combination of chromosomes from two primordial ancestors: the 66'66% of their genes from its diploid grandfather-great grandfather Ceterach javorkeanum, also called Asplenium javorkeanum, confined for millions of years in the Italian peninsula, the Balkans, Sicily and Turkey and 33'33% from its other diploid grandfather-great grandfather Asplenium semi-aureum, now considered extinct, but their genes survive in their hybrid offspring.

Family tree of the subgenus Ceterach ferns in the shape of their fronds. Drawing taken from the excellent article "Phylogenetic analysis of Asplenium subgenus Ceterach (Pteridophyta: Aspleniaceae) based on plastid and nuclear ribosomal ITS DNA sequences". http://www.amjbot.org/cgi/content/full/90/3/481

Another beautiful example of Ceterach lolegnamense in the same location as above.

  The thick layer of Selaginella denticulata seems to be almost essential for survival. If we start a bit of substrate is to be formed by the decomposed fronds of Selaginella denticulata mixed with remains of mosses and lichens and a few pieces of volcanic lava. The Selaginella denticulata, like plants that produce the mob lives on decomposing waste itself.

 Along with this group of Asplenium lolegnamense can see multiple copies of the Macaronesian endemism Aichryson villosum, a Crassulaceae, to bloom in early May.

New frond of Ceterach lolegnamense in early May. The pinnae are more slender than its parent Ceterach octoploideum.

 Frond last year with a beautiful yellow-green, a legacy of its father Ceterach aureum.

Sori still immature almost invisible under the thick layer of yellowish-white paleae lining the underside of the frond.

Mature sori in early May with conspicuous black sporangia about to disperse the spores. Enlarging the picture by double-clicking the details are better appreciated.

Mature sori after spore dispersal. Sporangia are appreciated and made of brown, protruding above the paleae.

Paleae of Ceterach lolegnamense, formed by a layer of dead and empty cells.

Sporangium of Ceterach lolegnamense with its ring of fire red cells and the bag ripped after spore dispersal.

Ceterach lolegnamense spores of a rather large size, characteristic of polyploid ferns. The spores of the diploid fern family Aspleniaceae never rarely exceed 39 μ, as in Asplenium javorkeanum, one of its ancestors.