Plant growth factors control or influence plant characteristics as well as adaptation. In general, there are two factors affecting plant growth and development: genetic and environmental.
The genetic factor is also called internal factor because the basis of plant expression (the gene) is located within the cell. The environmental factor is considered external, and refers to all factors, biotic and abiotic, other than the genetic factor. Both plant growth factors interact in various ways. The genetic factor determines the character of a plant, but the extent in which this is expressed is influenced by the environment.
A rice is always a rice; a corn is always a corn and cannot be a rice or anything else; a tree is distinct from other plant types, and so on. There are plants having special characteristics that are naturally adapted to watery places, to the desert, or to shaded conditions, or other ecological habitat (click to read Plant Classification Based on Natural Adaptation).
But the various characters that plants display are not necessarily exactly alike, even within the same species and clones. This deviation is more pronounced with plants that are grown at different periods of time, or in different locations, or with different amounts of care.
It is recognized that the genetic factor cannot cause a plant character to develop without a favorable environment. A crop variety may possess the genetic constitution which provides the blueprint for the plant to produce high yield; but without the proper nutrition and sufficient supply of other inputs, it will produce a dismal yield or worst, it may even fail to produce.
Increased yields can be achieved by growing crops under conditions where they are naturally adapted or by manipulating such conditions to favor their growth and development. Man in fact has learned long ago to manipulate the environment to grow plants away from their natural habitat for the purpose of research, pleasure or food, or for commercial use. An example is the Hanging Gardens of Babylon (click to read in What is Vertical Farming?) .
Another example is the Climatron at the Missouri Botanical Garden in St. Louis, Missouri, USA, with several climates under a 70-foot (21.3 m) glass dome, including tropical climate (Went and the Editors of Life, 1963). The tropical banana, which needs at least eight times as much water as that of tomato, has been grown in the desert (Belt, 2010).
Gigantic trees are often seen naturally growing on open field. But trees of the same species growing under harsh conditions with scant water and nutrient supply tend to become stunted. This interaction of the plant growth factors has been realized many centuries ago and widely applied with awesome effect in the creation of bonsai trees (click to read how bonsai rules were applied in pruning trees).
Manipulated by human hands through continuous root and shoot pruning and by growing them in shallow pots, large, gnarled and aged trees in miniaturized form have been created which have lived for generations, even surpassing the longevity of naturally growing trees.
Plants can also be made to adapt to conditions which deviate from their natural habitat through acclimatization, but only up to a certain point. In plant nursery management, the process of acclimatizing the seedlings in preparation for outplanting is called hardening.
The plant itself can, and has been, genetically engineered to produce cultivars with desirable characteristics including high yields, improved quality, resistance to pests and diseases, and tolerance to environmental stress.
In the 1970s, there was an outbreak of the grassy stunt virus which prevented rice from flowering and producing grain. The International Rice Research Institute (IRRI) found a gene for resistance to the disease in a wild relative, Oryza nivara, growing in India. The gene has, since then, been introduced into most varieties (Burness Communications, 2010).
With the advances in biotechnology, it has become possible to produce transgenic varieties, such as in tomato, corn, and other farm crops through recombinant DNA techniques.
In 1994 the Flavr-Savr tomato, the first transgenic variety, was released in the USA. It does not produce the enzyme polygalacturonase which is responsible for fruit softening. As a result, the tomato fruits remain longer attached to the plant without getting too soft. The tomato fruits also have longer shelf life. In corn, soybean, cotton, canola and potato, transgenic varieties have been produced that carry the endotoxin or Bt gene from the bacterium Bacillus thuringiensis for pest resistance (Lantican, 2001).
Another milestone in the manipulation of the plant growth factor is the Golden rice in which the provitamin-A biosynthetic pathway was genetically engineered into the endosperm. It is claimed that it was developed to prevent vitamin-A deficiency in developing countries (Potrykus, 2001).
Both plant growth factors, genetic and environment, can therefore be modified to serve man’s purpose in relation to crop farming.
Abellanosa, A.L. and H.M. Pava. 1987. Introduction to Crop Science. CMU, Musuan, Bukidnon: Publications Office. 245 p.
Belt, D. 2010. Parting the waters. National Geographic. 217(4):154-167.Burness Communications. 2010. Adapting agriculture to climate change: new global search to save endangered crop wild relatives. Retrieved January 2, 2010 from http://www.sciencedaily.com/releases/2010/12/101209201938.htm.