PHENOLOGY: WHAT IT STUDIES, METHODOLOGY, REAL STUDIES - BIOLOGY - 2025

The phenology is a scientific discipline that is responsible for studying the influence of the environment in different events recurring life cycles, typical of plants and animals.

The term was introduced by the Belgian botanist Charles Morren in 1849. The environmental factors that would be involved could be the climatic variations of a seasonal or annual nature, and those pertaining to the habitat, such as the elevation of the land.

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The biological cycle of living beings can be affected by the genotype and by different climatic factors. Currently it is possible to have information regarding the climate, biology and edaphic factors of the different crops.

In addition, the figures on the duration of the natural cycle and plant production are found in fairly accessible databases. However, it is possible that sometimes this information is not associated with each other, nor is it related to the effect they have on the morphology of plants.

Due to this, the use of phenological scales is important, since these would allow establishing a relationship between the biological information of the plant and the environmental factors that determined its development.

Importance and applications

Analyzes of phenological observations are very important. This is because they could tell farmers when to spray their plantations or help them set the right time to plant.

In addition, any variation in the phenological stages of plants would affect the trophic chain, considering that plants are the food base of herbivorous animals.

These records are also relevant in the medical area, since they would serve to evaluate the flowering seasons of herbs, whose pollen causes the disease known as hay fever.

What does phenology study? (object of study)

The objective of study of phenology is the description of the agents that cause the variations suffered by the different events. These are of a natural type and recurrent in nature, such as the flowering of an arboreal species or the appearance of a migratory bird in a specific region.

The idea is that correlations can be established between the dates of occurrence of the event, the climatic indices and the intervals of appearance between each one of them. This is why it is stated that in phenology there is a strategic integration between biology, ecology and meteorology.

Phenology is responsible for investigating the possible variations and reactions of a plant to different environmental factors, trying to predict its behavior in the face of possible new ecological environments. In addition, it makes chronological comparisons of the same event in a specific location.

In viticulture, studies establish a calendar of the annual growth stages. These can be used in the design of the vineyard and in the planning of the different human, material and economic resources that are needed for the development of the sowing.

Methodology

In a phenological investigation, observations can be carried out considering two types of variables:

- Independent variables. In this case, it would be a tool for conducting a microclimatic investigation, where the particularities of the environmental elements of a region are taken into account. An example would be the comparative study of the flowering of the pineapple plant, planted on two different dates, in the state of Carabobo, Venezuela.

- Dependent variables. In this case, biological events are used as indicators of the presence or absence of certain environmental factors.

-Qualitative methods

Local and regional information

One source that should be taken into account is the information that local inhabitants and scholars can offer. They could provide important data on the behavior patterns of the environment and the natural elements that comprise it.

Existing collections

Another way to obtain phenological data is the collections of plants that are part of the herbaria. Data may also emerge “ad libitum” from other specialists in the field or in related areas, whose work could provide relevant information to the study.

-Quantitative methods

Classic

This type of methodology is based on the collection of quantitative data. In this case, the number of trees bearing fruit could be recorded, without taking into account the difference in the amount of fruit produced by each plant.

Phenological quantification

In this method, the records show the quantified differences of each plant part: leaves, flowers or fruits, among others.

Each of these categories can be subdivided, for example, in terms of reproduction, flower buds, buds, flowers, seeds, among others, could be considered.

Production estimation

Depending on the object of the investigation, an estimate is sometimes required. These data may not offer a high degree of precision, since they are based on the averages that show the partial data found.

Quantification of species fallen on earth

If the study objects are not on the tree, but have fallen to the ground, they can be counted by trails. These are strips of approximately one meter wide, where the part of the plant under study (leaves, flowers or fruits) is collected, identified and counted.

Another way of counting them is to place containers suspended from the tree, where the falling fruits are collected, for example. These baskets can be placed randomly or on specific trees.

-Computation at the service of science

Currently there are computerized methods where phenological data can be studied and analyzed. To do this, the classical principles of phenology, phytosociological sampling techniques and the conceptualizations of growth analysis are taken as a basis.

This method establishes that the development of the phases of phenology is a process, where the variables are random sequences that evolve as a function of others.

In addition, it allows the realization of a quantitative, mathematical and statistical comparison between the object under study and the variables of the environment.

-Airborne sensors

New technologies that study the Earth from space allow entire ecosystems to be observed on a global scale, through the proxy approach. These novel methods complement the traditional way of obtaining and recording information.

Research conducted at the University of Arizona, based on the Enhanced Vegetation Index (EVI), used remote sensing to obtain a view of the Amazon rainforest during the rainy season. This showed that, contrary to what had been thought, during the dry season there was a notable growth of vegetation.

Phenological phases of plants

Initial phase

This stage begins when the seed is in a state of germination. During this phase, the plant is called a seedling and all the energy is directed to the development of new absorption and photosynthetic tissues.

Vegetative phase

In this period the plant needs more energy to satisfy the growth needs of the leaves and branches. The end of the stage is marked by the flowering of the plant.

Reproductive phase

It begins with fruiting. One of the main characteristics of this phase is the vegetative stop. This is because the fruits begin to develop, absorbing most of the nutrients that the plant obtains.

Identification of the phases

The extended BBCH scale is a coding system used to identify phenological stages. This is applicable in any variety of plants, both monocots and dicots.

One of its fundamental principles is that the general scale is basic for all species. Furthermore, the code used is common for the same phenological stage. It is important that recognizable external characteristics are taken to make the description.

Real studies in phenology

Plankton and climate

In 2009 an investigation was carried out in the North Sea, located between the coasts of Norway and Denmark. This was based on phenological changes in the plankton in that natural habitat.

Today, echinoderm larvae appear in plankton 42 days earlier, compared to 50 years ago. The same happens with the larvae of cirrepedes fish.

The research established that there is a close relationship between the increase of 1 degree centigrade in the temperature of that area, with the modification of the date in which the larval stages of these species appeared.

The alteration in the timing of the abundance of plankton could have effects on the higher trophic levels. If the zooplankton population fails to adapt to the new plankton characteristics, their survival could be compromised.

The impact of climate change on plankton affects the future of the marine bioecosystem. Furthermore, this has a significant influence on the environment at regional and global level.

Sunflower Crop Physiology

In 2015, a group of researchers conducted studies on sunflower cultivation. They concluded that a good planting process is the key to high yield in the crops of this plant.

In this study the physiology and agronomy of the sunflower crop were analyzed. This provided a basis for managing their crops and improving them at the genetic level.

The time between germination and sprouting of the seedlings should be short. This would allow obtaining plants of similar sizes, thus minimizing competition between species. In addition, the use of environmental resources would be maximized.

Soil temperature affects the duration of phenological stages. Furthermore, the differences between each sowing date influence these stages. Apart from these factors, humidity and soil management have a notable impact on the germination process.

The researchers maintain that there are several agronomic aspects that must be considered. The first would be the date and time in which the sowing is carried out, also considering the characteristics of the plants.

In addition to this, the space between each sowing row must be taken into account. In this way, it would improve the efficiency in the production of sunflower crops.

References

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3. Alberio, NGIzquierdo, LANAguirrezábal (2015). Sunflower Crop Physiology and Agronomy. Science direct. Recovered from sciencedirect.com.
4. J. Richardson (2009). Plankton and Climate. Science direct. Recovered from sciencedirect.com.
5. Robert B. Wallace & R. Lilian E. Painter (2003). Methodologies to measure fruiting phenology and its analysis in relation to frugivorous animals. Research gate. Recovered from researchgate.net.
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