The essential plant nutrients, or essential elements, are listed in the table below.
It enumerates 16 chemical elements of which the essentiality for plant growth and reproduction has been established according to the criteria formulated by D.I. Arnon and P.R. Stout in 1939.
This listing has existed since 1954 with chlorine as the latest addition (cited by Hopkins 1999)
Plant movements do exist.
Although unlike animals, plants are incapable of locomotion in that they are unable to move from one place to another, or perform some feat like shaking hands as humans do, they are still capable of some form of movement.
Plant organs move toward scarce resources or otherwise secure food or use movement as an adaptation to escape or minimize injury from harmful external factors or ensure development.
Thus, for example, the primary root moves downward where it can obtain water and mineral nutrients from deep down while the shoot moves upward to be exposed to light from the sun.
The types of leaves in most angiosperms may be broadly classified into simple and compound.
Simple leaves consist of a single blade such as those in corn, rice, banana, and mango whereas compound leaves have a blade that is separated into two or more parts on a common petiole, such as those in palms (e.g. coconut and African oil palm), legumes (e.g. soybean and peanut), malunggay or Moringa tree, and many ferns.
Earthworms are now highly regarded as a rich biological resource with a multitude of uses having commercial and environmental applications.
This is evident as shown by the vigorous interest that people around the world have accorded on such technologies as vermicomposting, vermiculture, vermimeal production, vermiceutical production, and vermiremediation.
This is a development that is not unexpected considering that more than a century ago, English naturalist Charles Darwin made the following concluding statement in his last and final book: The plough is one of the most ancient and most valuable of man’s inventions, but long before he existed the land was in fact regularly ploughed by earth-worms.
It may be doubted whether there are many other animals that have played so important a part in the history of the world, as have these lowly organized creatures (Darwin 1881).
6. Cohesion and Adhesion: Water molecules cling to each other and stick (adhere) to many surfaces.
The cohesive property of water is due to the hydrogen bonds which serve as a force of attraction between molecules to other molecules of water.
It is responsible for water’s continuous flow without breaking.
It is as if the hydrogen bond is a tying material that holds together a molecule and another molecule of water, preventing their separation.
The cohesion of water also accounts for the raindrops instead of mist, or the drops of water which fall from the margins of plant leaves early in the morning.
Where water drops get in contact with other drops without being subjected to considerable gravitational pull, they tend to be attracted and form a common cluster.
These cultural practices are recommended as a reference for calamansi growing in farms:
The planting distance for growing in the orchard under monoculture ranges from 4-6 m in a square, rectangular or triangular system.
This is equivalent to a calculated population density of about 278-719 trees per hectare, depending on plant-to-plant distance and the planting pattern to be adopted.
With 5 m x 5 m spacing in the square system, the population density per hectare will be 400. (click here to read Planting Patterns on the separate window)
3. Overdominance.
This is a type of dominance in which the heterozygote exhibits a measurable character that is significantly in excess of the characters carried by the two alleles making up the heterozygous genotype.
This is an in-triallelic interaction in which the two alleles in the same gene pair interact to outperform both phenotypic measurements carried by either parental alleles.
The Mendelian Law of Independent Assortment states that each gene pair acts independently of the other.
Gregor Mendel demonstrated that the transmission of traits involving one gene pair (monohybrid inheritance) following the Law of Segregation remains constant even in dihybrid crosses in which parents differ in two sets of characters.
Stated another way, the segregation of alleles in one gene pair proceeds independently of the segregation of alleles in other gene pairs during sexual reproduction.
Known also as Mendel’s Second Law, it provides the fundamental rule in genetics that the intraallelic interaction characteristic of the Law of Segregation is maintained regardless of the number of gene pairs constituting the genotype.
However, there are exceptions to this rule.
Intraallelic interaction is the interaction of alleles (e.g. between S and s or between T and t) belonging to the same gene pair (e.g. Ss or Tt) as distinguished from interallelic interaction which is the interaction of alleles belonging to different gene pairs within the same genotype such as S and s in the pair Ss with T and t in the pair Tt.
Table FC-1. List of fiber crops which are sources of textile, netting, and cordage fibers grouped by type of fiber.
Complete dominance is a type of dominance in which one allele in a single gene pair manifests itself fully in the heterozygote to the complete exclusion of the other, contrasting allele.
It was discovered by Gregor Mendel in his monohybrid study with garden pea.
Thus at the beginning of his report (Experiments on Plant Hybridisation, Mendel 1865), he introduced the terms dominant and recessive. Here’s a quotation:
Henceforth in this paper those characters which are transmitted entire, or almost unchanged in the hybridization, and therefore in themselves constitute the characters of the hybrid, are termed the dominant, and those which become latent in the process recessive.
The expression ‘recessive’ has been chosen because the characters thereby designated withdraw or entirely disappear in the hybrids, but nevertheless reappear unchanged in their progeny, as will be demonstrated later.