independente do seu contexto: gema (a and b)ou porta-enxerto (c)?

Random House

Hort.
a. a bud, shoot, or scion of a plant inserted in a groove, slit, or the like in a stem or stock of another plant in which it continues to grow.
b. the plant resulting from such an operation; the united stock and scion.
c. the place where the scion is inserted.

Acredito que seja isso aí.

Trata de propagação. acredito que a gema de que falam seja gema apical.

cuttings or (apical) buds



Ref:

diferentes números de folhas e presença ou não da gema apical. Coletaram-se estacas herbáceas de ... São sintetizadas no meristema apical e nas folhas ...
www.ufpel.tche.br/faem/agrociencia/v10n1/artigo06.pdf

COMPRIMENTO DAS ESTACAS NO ENRAIZAMENTO DE MELALEUCA. EFFECT OF CUTTING LENGTH IN ROOTING OF TEA TREE. Yohana de OLIVEIRA. 1. André Luís Lopes da SILVA ...
www.sumarios.org/pdfs/802_4563.pdf

Por gentileza, veja abaixo

Os principais métodos de propagação assexuada são: a estaquia e a enxertia. O primeiro consiste na retirada de pequenos ramos (ou estacas) das árvores, os quais são colocados em propagador para que ocorra a regeneração de raízes e de ramos. Daí surgem as novas plantas.

A enxertia é um método de propagação mundialmente consagrado na produção de mudas de espécies frutíferas. É a união de uma gema ou de um fragmento de ramo de uma planta adulta com uma planta jovem. A planta enxertada passa a se constituir numa única e nova planta.
http://blog.tudosobreplantas.com.br/2007/02/

Grafting is a method of asexual plant propagation widely used in agriculture and horticulture where the tissues of one plant are encouraged to fuse with those of another. It is most commonly used for the propagation of trees and shrubs grown commercially. (Grafting is limited to dicots and gymnosperms. Monocots lack the vascular cambium required.)

In most cases, one plant is selected for its roots, and this is called the stock or rootstock. The other plant is selected for its stems, leaves, flowers, or fruits and is called the scion. The scion contains



--------------------------------------------------
Note added at 13 mins (2009-01-16 19:31:10 GMT)
--------------------------------------------------

Link da referência em inglês abaixo.

http://en.wikipedia.org/wiki/Graftingwe

--------------------------------------------------
Note added at 1 hr (2009-01-16 20:25:03 GMT)
--------------------------------------------------

Rootstock
From Wikipedia, the free encyclopedia
Jump to: navigation, search
A rootstock is a plant, and sometimes just the stump, which already has an established, healthy root system, used for grafting a cutting or budding from another plant. The tree part being grafted onto the rootstock is usually called the scion. The scion is the plant which has the properties desired by the propagator, and the rootstock is the working part which interacts with the soil to nourish the new plant. After a few years, the tissues of the two parts will have grown together, producing a single tree although genetically it always remains two different plants