维生素C能提高作物种子产量

Biochemists at the University of California, Riverside report a new role for vitamin C in plants: promoting the production of twins and even triplets（三胞胎） in plant seeds. Daniel R. Gallie, a professor of biochemistry, and Zhong Chen, an associate research biochemist in the Department of Biochemistry, found that increasing the level of dehydroascorbate reductase (DHAR), a naturally occurring enzyme that recycles vitamin C in plants and animals, increases the level of the vitamin and results in the production of twin and triplet seedlings in a single seed.

The value of the discovery lies in the potential to produce genetically identical seedlings and increase production of high-value crops.

"The ability to increase fertility can be extremely useful when the inherent（固有的） rate of fertility is low or the value of the crop is great, such as corn in which the production of multiple embryos would significantly boost its protein content," Gallie said. "The extra seedlings per seed may also enhance per-seed survival chances for some species."

Study results appear in the online journal PLoS ONE.

Just as in humans, twins in plants can be either genetically identical or fraternal（友好的） . Gallie and Chen discovered that the twins and triplets produced in tobacco plants when vitamin C was increased were true twins or triplets as they were genetically identical.

In the lab, the researchers went on to show that injecting plant ovaries with vitamin C was sufficient to produce twins or triplets and that the vitamin causes the zygote（受精卵） , the fertilized egg, to divide into two or even three fertilized egg cells before these cells proceed through subsequent stages of development to produce twins or triplets.

Although they used tobacco in their research, Gallie predicts vitamin C could generate twins and triplets in other plants as well.

"Because the early stages of embryo development are so conserved among plant species, we expect that vitamin C will have a similar effect in almost any plant," he said.

A question raised by the study is whether vitamin C might have a similar effect in humans. In contrast to most animals, humans cannot make vitamin C and it must, therefore, be obtained regularly from dietary sources.

"Although the development of plant and animal embryos differ in many respects, the manner in which the genetically identical twins were produced in our study is similar to that for identical human twins in that it is the very first division of the fertilized egg into two separate cells that produces the two separate embryos, resulting in two seedlings in plants or two fetuses in humans," Gallie said. "Despite the differences in the subsequent development of embryos in plants and humans, the critical effect of vitamin C is on this very first cell division."

To Gallie's knowledge, no study linking vitamin C to twins in humans has been carried out to date.

"Humans are mutants in that we lack the last enzyme in the pathway needed to produce vitamin C," he said.