Chapter 31: Propagating plants and developing new plants
Chapter 31: Propagating plants and developing new plants
Ancient agriculture required plant propagation, making new plants. Plants don’t live forever and many crops are annuals or are harvested less than a year after planting. Although the earliest agricultural efforts may not have involved intentionally propagating plants, fundamental to the development of agriculture was the acknowledgment that making new plants is an essential part of the process. The techniques used to propagate plant crops vary depending upon the crop. For most familiar crops it required storing some seed (i.e. not eating it) and planting it at some point in the future. For crops such as cereal grains and most legumes, where the seed is the part that is harvested and eaten, development of the ‘store and plant’ technology was relatively straightforward and rapid. However, crops such as tomato, squash and eggplant, where a fleshy fruit is harvested and the seeds are small and inconspicuous, required more technology: a recognition that seeds were present in the fruit and a method for processing of some of the fruit to obtain seeds for planting. Perennial plants do not require propagation each year, they could be maintained without propagation. But eventually they required some means of making new plants, especially if the agriculturalists are moving to a new area. For reasons discussed below, propagation of perennial plants often did not involve seeds but instead asexual means of propagation.
For most of its existence agriculture did not involve attempts to produce novel plants, plants with characteristics that distinguished them from their parents. However, the hope from the earliest onset of agriculture was that one might be able to improve the characteristics of the crop, producing crops that yielded more, tasted better, stored better, were easier to harvest, and were more tolerant of hardships, in particular, more tolerant of disease. Primitive farmers were happy when they found desirable novelties and were able, knowingly or unknowingly, to gradually change the crops they grew. But they did not have the understanding and technology to intentionally create something novel. This has become possible over the last 100 years. Although an understanding of aspects of asexual reproduction was important for some crops, it was the recognition of the sexual process in plants, in particular the functioning of flowers and pollination, that has been critical to the development of the technologies of crop improvement (Fig. 2). All of the major crops have been, and continue to be, intentionally modified. And this is one of the many factors that has changed, and made more complex, the business of agriculture. Where it was once basically controlled by a farmer who served both as a producer and salesman, it is now a vastly more involved system that depends on farmers, seed producers, researchers, fertilizer producers, equipment manufacturers, agricultural scientists, the government, and vast