David from Goliath?

You got that pack of seeds you've been waiting for, so you plant them carefully in your best germinating mix and wait for signs. If you got one of those seed packets with a picture of your hoped-for plant on it, you spend time looking at that picture, or searching the internet for more information about your baby. Your anticipation knows no bounds. But what happens when something totally unexpected springs up in your seed tray?

The plants shown in the thumbnail picture at right are full grown, yet in a small pot. Care to guess what kind of seed produced these plants, or would you even hazard a guess as to what kind of plants they are? Well, they came from one Alocasia seed, and that seed came from a large specimen of Alocasia odora. So those very diminutive plants are actually what I call the smallest Alocasia in the world, Alocasia x microdora. However, this plant was not the result of crossing a small growing Alocasia with A. odora, but rather a wild-pollinated seed set, most likely a self-pollination.

Sports in the field!

One term for this type of occurrence is the appearance of a sport. Sports, in botany, are plants that show characteristics not normally seen in the species, such as abnormal growth or color. In this case, the characteristic is abnormally small growth. Unfortunately, another characteristic this plant had was abnormal sensitivity to rot, and because of this I have the plant no longer. However, this is not the first time I have seen this phenomenon. Years ago, when germinating some seed from Syngonium fruits, I obtained three different extremely dwarf sports. These plants grew normally in every way, except that the leaves grew no larger than about one inch long on thin vining stems. A normal Syngonium vine has leaves six or more inches long when juvenile, and palmately compound leaves when mature. In this case, the seed was not the result of a hybridization either.

A sporting chance

Alocasia x calidora sport

Special plants can occur when hybridizing as well, but to be sure they are a sport and not just the result of mixing the two sets of genes together, the difference has to be one that neither parent exhibits in the least. I have had several of these show up in hybrid seed batches. The first time I saw them was when I germinated seed produced by the cross which yielded Alocasia x calidora, or what is known by some as "Persian Palm" (neither a palm, nor from Persia!). The picture at left shows a mature version of one of several that appeared in the seedling trays. I chose to call these "Pixie Teardrops" due to the shape of the leaves. None of these have ever produced blooms for me. As a breeder and scientist, this is no surprise because I suspect that what I have seen in these plants is an example of a plant with a high ploidy. Ploidy refers to the number of sets of chromosomes in a cell. Normal ploidy is two sets of chromosomes, or diploid. Plants like the Pixies are very likely to have 5 or more sets of chromosomes due to an early failed or incomplete cell division after ovule fertilization. Once the pollen cell has fused with the ovule cell (each haploid or with only one set of chromosomes), a diploid cell is formed. Then, in preparation for division, the chromosome complement is doubled within this newly formed cell. For a short time, the cell has four sets of chromosomes, but these pull apart into two sets as the cell divides into two, yielding two cells, each with two sets of chromosomes. At least, that is what happens when everything goes normally. But in the case of a plant like the Pixie, the first cell may fail to divide, and so the cell becomes tetraploid, or a cell with four sets of chromosomes. A subsequent incomplete cell division can yield an even higher ploidy. Plants with excessive sets of chromosomes are usually dwarfed when compared to their normal counterparts, and their leaves are thicker.

Another possibility is that one of the sex cells, or gametes, may have formed abnormally, yielding a diploid gamete instead of a haploid one. On fusion with the opposite sex cell, an uneven ploidy, such as triploid (three sets of chromosomes) would result. Such a cell would produce a sterile plant because three cannot be divided evenly into two, as must happen to produce viable gametes.

Thus I have shown you how you can have sports mixed with gardening. So watch your seed trays closely, for you may discover something unusual and interesting popping up there!

Photo credit: LariAnn Garner, Aroidia Research