In its life cycle, a plant travels through many phases. Embryonic development, adolescence, maturity, senescence, and death are the phases.
A plant’s juvenility is a period of growth during which it is unable to blossom. The duration of juvenility differs amongst plant species. The juvenility period of annual plants is quite brief, while perennial plants have a long juvenility period.
Table – Juvenile period of some plants
Characteristics of Juvenility
Leaf Form- In its juvenile stage, the leaf is very active. Some plants, such as Acacia sp., have different leaf morphologies in their juvenile stages.
Growth Form- The young branch resembles a whip. The branch develops in a straight line parallel to the main stem. Citrus, Guava, and other fruits have such a branch, which is known as a water sprout.
Presence of thorns- Some fruit trees have thorns when they are young or juvenile, but these thorns vanish as they reach adulthood. Apple, pear, citrus, and other fruits are examples.
Leaf Retention – In the juvenile stage, plants do not lose leaves all year. In the adult or mature stage, however, it is shed.
Root Emergence – The root develops quickly when the plant’s juvenile components are employed in propagation.
Flower Bud Differentiation
Bud- The bud is an immature branch system that is frequently enveloped by scale leaves for protection. A lateral branch, a flower, or an inflorescence emerges from the bud. The development of these buds into flowers or inflorescences is an important part of fruit production. The phases of flower growth are as follows:
1. Flower bud differentiation- Flower induction is another name for it. Bud differentiation requires increased cell division below the apical section of the meristem in the middle area. Parenchyma cells develop into flower primordia that surround the meristem as a result of cell division.
2. Initiation – In the second initiation, flower development takes place.
3. Development of Flowers- This includes the time between induction and bloom. The bloom is normally open to pollination at this time. The ultimate step of development is the flower’s opening (anthesis).
A flower is a modified reproductive branch, which is essentially a stem with an apical meristem that produces leaf primordia.
Table- Flower bud differentiation and flowering in some important fruits
Types of buds
1. Simple Bud –It grows from vegetative branches. Leaf bud is another name for it.
2. Mixed bud- It takes the form of a flower-bearing stalk. A flower bud is another name for it.
3. Compound bud –It grows on both the leaves and the blooms.
Factors affecting flower bud differentiation
The following endogenous and exogenous variables are involved in flower induction signals:
1. Endogenous factors
a) Carbon: Nitrogen Ratio (C: N Ratio): A high nitrogen-to-carbohydrate ratio promotes blooming. In immature plants, excessive nitrogen use delays blooming by reducing the C:N ratio. Plants that are old, feeble, or have a high C:N ratio are more likely to blossom profusely. There are four possible scenarios when it comes to the C:N ratio:
i) Flowering with a high nitrogen and low carbohydrate content
ii) Flowering with enough of nitrogen and glucose
iii) Good growth and blooming with moderate nitrogen and carbohydrate.
iv) Only a few buds developed due to low nitrogen and high glucose levels.
Photosynthesis results in the buildup of carbohydrates that assist maintain the right C:N balance while the plant is not growing. Photosynthesis occurs during the active growth phase, changing the C:N ratio and, as a result, affecting flowering.
b) Genes – Synthesize the gene eafl as plants transition from juvenile to adult phase. The influence of the juvenile stage, which causes early blooming, is reduced by this gene. The HST gene, on the other hand, increases juvenility in plants.
2. External factors
A) Environmental factor
Termperature
Synthesize the gene eafl as plants transition from juvenile to adult phase. The influence of the juvenile stage, which causes early blooming, is reduced by this gene. The HST gene, on the other hand, increases juvenility in plants. The main environmental factor linked to flowering is temperature. The abundance of flowers in the spring is a common occurrence. Flowers bloom at the same time every year due to the availability of a specific temperature in the spring. The plant benefits from being exposed to cooler temperatures before flowering in the spring. When exposed to temperatures ranging from 0 to 10 degrees Celsius, biennial plants such as carrots, celery, cauliflower, cabbage, turnips, and others begin flowering. Vernalization is the term for this process. The chilling requirement is the term for the low-temperature requirement in certain situations. For bud blossoms in the spring, they need to be chilled below 7 degrees Celsius for 4 to 60 days.
Table-the chilling requirement of some temperate fruits
Photoperiod Some plants will only blossom if their photoperiodic requirements are met. Plants are divided into three groups based on their light period:
.Long day plant (LDP): –Only when the day is longer than 12 hours or more than 12 hours can flowering occur.
.Short day plant (SDP): – When the day is fewer than 12 hours long, these plants bloom.
.Day Neutral Plant (DNP): – The duration of the day has no effect on the flowers of these plants.
Light
Bud differentiation and blooming are influenced by light intensity, duration, and quality. When it comes to blossoming, more light intensity is preferable to low light. This is why a fruit tree’s outside branches produce more fruit than its interior branches. Flowering is stimulated by red light (sunlight), but it is inhibited by far-red light. As a result, the quality of light has an impact on blooming.
B) Managemental Factor
1. Nutrients- The plant’s vegetative or reproductive growth is determined by nutrients. The plant’s vegetative development is aided by nitrogen. It also improves the plant’s glucose consumption. In plants, phosphorus is involved in protein synthesis and cell division, while potassium is involved in sugar transport. Other nutrients are also important in blooming and bud differentiation.
2. Moisture- The lack of moisture extends the time it takes for flower buds to differentiate. When there is a dearth of water, flowering primordia are less developed.
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