**8. Climate and flowering**

Blooming or flowering is a featuring phenophase which usually heralds the arrival of spring season. Flowering is controlled by environmental conditions and developmental regulation. The complexity of this regulation is created by an intricate network of signaling pathways [13]. The plant Arabidopsis is a model for the study of flowering mechanism due to the significant number of environmental factors involved in this process for many other species. In addition, the genetic material of this plant is well developed. Many factors influence the flowering such as photoperiod, growth regulators, insolation and sunlight, circadian clock regulation, temperature, and chromatin structure [13].

## **8.1 Photoperiod role in flowering control**

One of the most important factors controlling flowering time in temperate regions is the duration of the daily light period, or photoperiod. Plant genes involved in sensing the photoperiod were identified by the molecular genetic approaches. These genes encode the proteins responsible of the flowering process and its

**35**

**Figure 2.**

*Climate as the Major Factor Controlling Phenology DOI: http://dx.doi.org/10.5772/intechopen.95893*

regulation according the environmental conditions. Other genes encodes the compo-

The **Figure 2** illustrates the relations among factors, genes, and processes involved in flowering phenology relating to the photoperiod. The effect of photoperiod on flowering consists of a balance between genes which promote the flowering in green color in the **Figure 2** and in red color those which repress the flowering. All these genes are incited by the sunlight. While Repressive effect is represented by the perpendicular arrows, and overexpression of genes is illustrated but e small upright arrows, the promotion is represented by arrows between genes. Similarly, interaction between proteins is indicated by simple lines. The expression of genes controlled by circadian clock is noted by arrows from it whereas arrows to the clock

nents of light signal pathways and components of the circadian clock.

are for the process of lengthening the period by the gene [13].

identified by scientist as to be the gene (per, frq, clock, tau) [14].

**8.2 The role of the circadian clock and the central oscillator in flowering**

Biological Phenomena are almost systematic and have standard rhythm, timing and cyclicity. These are all controlled and adjusted by the biological clock or the circadian clock. This rhythmicity is at all living beings and in every division of time from one second to one year. The genes controlling the circadian clock have been

The period of circadian clock is almost one day without being affected by transition between day and night, dark and light. This clock is observed in all functions and biological elements from stomat, CO2 assimilation, and gene transcription to the clearly observable phenophases like defoliation, bud burst and flowering. This rhythmicity and circadian are believed to be created by the cyclicity of environmental phenomena and hence underwent a selection pressure. Indeed this circadian clock serves the harmony between environment with it climates and the phenology and therefore permit to living beings to efficiently anticipate their environment changes in particular periodic variations or more appropriately the

*Signaling pathways involved in the regulation of flowering by photoperiod in Arabidopsis source: Reference [13].*

#### *Climate as the Major Factor Controlling Phenology DOI: http://dx.doi.org/10.5772/intechopen.95893*

regulation according the environmental conditions. Other genes encodes the components of light signal pathways and components of the circadian clock.

The **Figure 2** illustrates the relations among factors, genes, and processes involved in flowering phenology relating to the photoperiod. The effect of photoperiod on flowering consists of a balance between genes which promote the flowering in green color in the **Figure 2** and in red color those which repress the flowering. All these genes are incited by the sunlight. While Repressive effect is represented by the perpendicular arrows, and overexpression of genes is illustrated but e small upright arrows, the promotion is represented by arrows between genes. Similarly, interaction between proteins is indicated by simple lines. The expression of genes controlled by circadian clock is noted by arrows from it whereas arrows to the clock are for the process of lengthening the period by the gene [13].

### **8.2 The role of the circadian clock and the central oscillator in flowering**

Biological Phenomena are almost systematic and have standard rhythm, timing and cyclicity. These are all controlled and adjusted by the biological clock or the circadian clock. This rhythmicity is at all living beings and in every division of time from one second to one year. The genes controlling the circadian clock have been identified by scientist as to be the gene (per, frq, clock, tau) [14].

The period of circadian clock is almost one day without being affected by transition between day and night, dark and light. This clock is observed in all functions and biological elements from stomat, CO2 assimilation, and gene transcription to the clearly observable phenophases like defoliation, bud burst and flowering. This rhythmicity and circadian are believed to be created by the cyclicity of environmental phenomena and hence underwent a selection pressure. Indeed this circadian clock serves the harmony between environment with it climates and the phenology and therefore permit to living beings to efficiently anticipate their environment changes in particular periodic variations or more appropriately the

**Figure 2.** *Signaling pathways involved in the regulation of flowering by photoperiod in Arabidopsis source: Reference [13].*

#### *Agrometeorology*

seasonality of climatic elements including temperature, insolation by its intensity and photoperiod, humidity, precipitations [14]. This implies the constant quality of this circadian clock and meanwhile poses a problem of adaption to the unexpected climates changes. Thus, many vulnerable species may have been extinguished due to this effect.

Three outstanding interrelated types of this rhythmicity are characterized in the circadian clock including the input pathways which are relating to the daily cycle of light and dark and adjusting the clock mechanism to it. Secondly, a central oscillator which is responsible to keep the mechanism of 24 hours' time. And output pathways for specific process as the thirds category of this circadian clock [13].

#### **8.3 The role of the vernalization on flowering**

As a commonly used technique, vernalization is used since a long history of agriculture. First discovered for plants which were planted in spring, then they needed some cold to germinate and to pass from vegetative life to productive life. Indeed, vernalization is almost related to flowering and fructification in particular. And it is defined as subjection of seeds and seedlings to coldness or chill in order to promote and hasten the growth and the flowering of plants.

In fact, plants are very sensitive to their environment and constantly adapting to the environmental variations by for example dormancy or overwintering during adverse conditions period which is a strategy to withstand them. However, in spite of its toughness, winter cold is in the other hand mandatory and indispensable for plant growth and flowering whence the principle of vernalization. This vernalization is also an adaptive trait to prevent flowering before the spring arrival with its favorable conditions. Genetically, vernalization is merely the inhibition of genes which repress flowering particularly in Arabidopsis and cereals [15].

Exposure to low temperatures for several weeks will often accelerate flowering. Susceptibility to this treatment can differ markedly between varieties of a species. Therefore winter seasons is likely to an inevitable period in the plants life cycle because without long exposure to cold plants do not flower not pass to the reproductive and productive phase of their life. During winter plants are in vegetative growth phase with the minimum of activities [13].

**Figure 3** illustrates process, mechanism and all involved factors and genes in the flowering phenomenon, especially promotion of this flowering process is indicted in blue and the red color illustrates the components and genetic interaction which repress flowering including FLC (Flowering Locus C) and its relatives pointed as FLC clade. It inhibits the expression the flowering genes or properly named the floral integrator genes which are FD, FT, and SOC1 (Suppressor Of CONSTANS1). The photoperiod pathway passes by CO (CONSTANS) to induce the FT which is a protein working as a mobile signal of flowering. In the floral meristem, FT in partnership with FD protein activate SOC1 as well as SAP (sepalat), FUL (fruitful), and AP1 (apetatalata1) which are known as the floral meristem identity genes and which induces the floral meristems that will develop into flowers. Accordingly, Flowering locus C (FLC) and photoperiod pathway are antagonist.

In the one hand, Autonomous pathways genes partially determine the expression of FLC. In the other hand, the prolonged winter and cold further repress the FLC remodeling of chromatin. In addition, flowering is promoted by the plants hormones class of gibberellin which activates SOC1 along with the floral meristemidentity gene LEY (LEAFY) [15].

As illustrated by **Figure 4**, vernalization, which repress FLC expression, along with the autonomous pathway genes induce flowering [13].

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*Climate as the Major Factor Controlling Phenology DOI: http://dx.doi.org/10.5772/intechopen.95893*

**9. Climate and fructification**

*FLC source: Reference [13].*

*Outline of flowering pathways in Arabidopsis source: Reference [15].*

**Figure 3.**

**Figure 4.**

desirable to the consumer [16].

The making of a fruit is a developmental process unique to plants. It requires a complex network of interacting genes and signaling pathways which consists of series of reaction launched by an environmental signal such as light, photoperiod, and temperature. Generally, fructification goes through three stages which are first the set of fruit which follows the pollination of flowers. Then the fruit development stage and finally the fruit ripening which received the most attention of researcher of the field. This is due its importance in commercialization an economy since it the quality of fruits is the most attractive feature for the customer. In fact the process of ripening activates a series of biochemical reactions that make the fruit edible and

*The effects of Vernalization and the autonomous pathway on flowering time, emphasizing the central role of* 

A detailed illustration of this process is provided by the following **Figure 5**. It is merely a scheme of activating the ripening related genes to be expressed into enzymes charged each of which by one or more of the various ripening pathways such odor, color or softening. This whole process is controlled and adjusted by hormonal and environmental signals. It is to be noted that ethylene as a plant hormone plays a major role in this process of ripening and fruit development [16]. Indeed,

#### *Climate as the Major Factor Controlling Phenology DOI: http://dx.doi.org/10.5772/intechopen.95893*

**Figure 3.** *Outline of flowering pathways in Arabidopsis source: Reference [15].*

#### **Figure 4.**

*The effects of Vernalization and the autonomous pathway on flowering time, emphasizing the central role of FLC source: Reference [13].*

#### **9. Climate and fructification**

The making of a fruit is a developmental process unique to plants. It requires a complex network of interacting genes and signaling pathways which consists of series of reaction launched by an environmental signal such as light, photoperiod, and temperature. Generally, fructification goes through three stages which are first the set of fruit which follows the pollination of flowers. Then the fruit development stage and finally the fruit ripening which received the most attention of researcher of the field. This is due its importance in commercialization an economy since it the quality of fruits is the most attractive feature for the customer. In fact the process of ripening activates a series of biochemical reactions that make the fruit edible and desirable to the consumer [16].

A detailed illustration of this process is provided by the following **Figure 5**. It is merely a scheme of activating the ripening related genes to be expressed into enzymes charged each of which by one or more of the various ripening pathways such odor, color or softening. This whole process is controlled and adjusted by hormonal and environmental signals. It is to be noted that ethylene as a plant hormone plays a major role in this process of ripening and fruit development [16]. Indeed,

**Figure 5.**

*Schematic representation depicting the molecular mechanisms controlling the ripening of climacteric fruit*  **source:** *Reference [16].*

fruits whose ripening is related to ethylene and a respiration increase are called climacteric fruit, such as tomato, apple, pear, and melon. In the other hand, the non-climacteric are featured by no ethylene associated with the increase and peak of respiration during the ripening phase. It is to note that sales men uses this ethylene to preserve fruits during transportation or deposit for long-period by picking fruits prematurely and when ready for exposition for sale they use ethylene to induce ripening. Similarly, it is used to advance flowering before the adverse periods.
