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More berries
In article ,
wrote... MMMavocado schreef Avocado is a one-seeded berry. The papery membrane surrounding the cotyledons is seedcoat. In the Mexican (Persea americana ssp. drymifolia) and Guatemalan (P. americana ssp. nubigena) races, there is a single seedcoat. In the West Indian race (P. americana ssp. americana), the coat is separated into two distinct layers. But I've never heard anyone suggest that the outer one is endocarp. + + + Thank you! Well, Mel, it is official now ... I wasn't quite completely convinced by the above, since I'd seen some equally authoritative-sounding [for all that's worth!] statements elsewhere that conflicted. [But see below for strong support.] I'd hesitated at first because I'd vaguely remembered reading somewhere that avocados actually varied as to whether there was an appreciable development of a hard endocarp [possibly the same differences pointed to above?], and thus would vary as to whether the fruit would be classified as a drupe or as a 1-seeded berry. I then checked briefly, and initially didn't find anyone calling the fruit a berry, but did find several calling it a drupe: http://www.csdl.tamu.edu/FLORA/Wilson/pp/f97/fruits.htm or http://www.csdl.tamu.edu/FLORA/Wilso...u98/fruits.htm "II. Other fruits and fruit-like structures: 3. DRUPE: Single carpel, single-seeded, pericarp tissue differentiated into THREE layers: EXOCARP, MESOCARP, ENDOCARP: Peach - exocarp with fuzz Nectarine and Plum - exocarp without fuzz Almond - exocarp/mesocarp removed, just PYRENE [=endocarp and seed] Avocado - endocarp VERY thin Coconut - mesocarp fibrous ,[dispersal], testa thin, endosperm both solid [meat] and liquid [milk] Raspberry - an AGGREGATE (separate ovaries of one flower joined together) of small drupes [druplets]" [...] "TAXA EXAMINED - FRUIT LAB LOCAL NAME GENUS SPECIES FAMILY CLASS FRUIT TYPE Carpel# [...] Avocado Persea americana Lauraceae Dicot Drupe 1" http://www.csdl.tamu.edu/FLORA/Wilso...g/laupage1.htm "The Magnoliidae Family Overview - The Laurales Lauraceae - the Laurel Family The typical fruit type for the family - a drupe - is encountered with the avocado (Persea americana) - the exocarp is peeled, the mesocarp is fleshy, and the endocarp is reduced to a thin, brown covering of the avocado seed." http://flora.huh.harvard.edu:8080/fl...taxon_id=10479 "5. Lauraceae Jussieu Laurel Family [..] Fruits drupes, drupe borne on pedicel with or without persistent tepals at base, or seated in ± deeplycup-shaped receptacle (cupule), or enclosed in accrescent floral tube. Seed 1; endosperm absent." [...] "8. Persea Miller, Gard. Dict. Abr. ed. 4. 1754. [...] Drupe dark blue to black, nearly globose, borne on pedicel with tepals persistent at base; cupule absent." http://pas.byu.edu/AgHrt100/avocado.htm "The fruit is a drupe, having a stony endocarp." But the "berry" description is gaining strong support: http://www.cas.muohio.edu/~meicenrd/...logy/dln11.htm Lauraceae (Laurel Family) [...] "III. Fruit A. 1-seeded berry or drupe" http://www.botgard.ucla.edu/html/bot...sea/index.html "This berry is truly unusual, not only because it is oily, not sweet, but also because it never softens while still on the tree, where it remains hard and continues to grow. [...] The peel or rind (exocarp) consists of an epidermis with a cuticle, but in the warty fruits, the epidermis is replaced with cork from a cork cambium. The warts or bumps are airy zones in the cork called lenticels. Beneath this are several layers of cells, the innermost ones being sclerenchyma. The thick, green mesocarp is composed of millions of small parenchyma cells, some that are specialized for oil storage and others that have smaller amounts of oils. The endocarp consists of several layers of thin-walled cells. In the center, the seed has a double seed coat, two cotyledons rich in starch, and a relatively small embryo." http://www.cabi-publishing.org/books...1993575Ch2.pdf Seems like a nice botanical treatment of the avocado. ["p. 16" (= 2nd page of the link)]: "Fruit small, globose to large fleshy, obovoid one-seeded berry in subgenus _Persea_." [p. 30] "The avocado fruit is botanically a one-seeded berry (Fig. 2.3f), and is very variable in size (50 g to nearly 2 kg), shape (round, oval, pyriform), rind characteristics (thickness, surface features, colour), flesh, and seed characteristics (size, tightness in cavity, etc.). Cummings and Schroeder (1942) described basic fruit anatomy. [...] The innermost flesh is a rather indistinct endocarp, made up of a few rows of smaller, more flattened parenchyma cells. It is botanically incorrect to refer to the flesh as a mesocarp, as by definition the flesh of a berry fruit comprises mesocarp plus endocarp." [p 32] "The role of previously unreported tissues in avocado fruit development has been outlined by Steyn et al. (1993) they not that the vascularized part of the seed coat is actually a pachychalaza, with the testa (the contribution of the integuments) representing only a very small non-vascularized portion." refs cited above: Cummings, K and Schroeder, C. A. 1942. Anatomy of the avocado fruit. California Avocado SocietyYearbook 1942, 56-64. Steyn, E. M. A., Robbertse, P. J., and D. Smith. 1993. An anatomical study of ovary-to-cuke development in consistently low-producing trees of the "Fuerte" avocado (Persea americana Mill.) with special reference to seed abortion. Sexual Plant Reproduction 6: 87-97. cheers |
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