BLOSSOM END ROT CAUSES AND TREATMENTS
BLOSSOM END ROT
 |
| Blossom end rot in Tomatoes |
 |
| Blossom end rot on sweet pepper |
 |
| Blossom end rot on water melon |
Blossom end rot is
the watery softening and gradual brown to dark development at the soft end
portions of some fruit vegetable crops especially in the solanacae and
cucurbitacae family. It occurs when the developing fruit is deprived of water
and sugar.
The four main known causes are explained below
- Moisture stress (excess or inadequate): water is a solvent that creates solution for nutrient and water uptake. It also softens the soil for easy root development. The main function of the root besides anchorage is for water and nutrient absorption. Before a root can effectively absorb water, then the leaf should have lost some water. The root and leaf always maintain a balance between what is lost and what is absorbed. Yet the rate of water absorption and water flow through the plant is dependent on the environment surrounding the plant to create the necessary stress to cause the plant to transpire. The rate at which plants lose water is influenced by the make-up of the plant itself and the surrounding environment. While plants appear to have built in mechanism to protect them from inadequate moisture, they appear to have virtually no ability to protect them from excess moisture. If plants have excessive moisture supply, plants cannot increase the rate of which they lose water to help dry out the growing media. This leads to oxygen deficiency. This creates saturation at the root level. When this happens for 48 hours (deprived of oxygen),the plant growth becomes sluggish, nutrient deficiencies occur, the roots get soaked and die. When this happens, though there is enough water in the fruit, yet it will be deprived of sugar. This results in blossom end rot. The solution to this is to facilitate the removal of water from the media, which helps to draw oxygen to the roots.
On the other hand ,if there is
insufficient moisture available to the plant, the plant adapts to the situation by releasing the stress
hormone Abscisic Acid which can influence the plant to reduce the rate of water
being loss through developing fewer and smaller leaves, thicker cuticle,
reducing the number of stomata or shedding the leaves to drastically lower
transpiration, develops more roots to increase capacity to absorb more water
and directing more sugars to the rot or switching the development from
vegetative to reproductive phase . The amount of water that plants lose outside
is greater that needed for photosynthesis. Plants have linear flow of water; where water is absorbed by the roots,
relocates upwards through the stem to the leaves, flowers, and fruits where it
exits through the stomata. Where water is not adequate the reverse of water
transportation occurs. The fruits (fruit tip or the soft growing points) are
first to be deprived of water, followed by flowers, then the leaves( at extreme
cases, these drop, fold, shrink or wilt) and finally to the root. Hence this
cause the blossom end rots with a minimal imbalance in absorption and
transpiration.
Another situation is where there
is excessive transpiration, when plant loses more water than it is absorbing
water, the water is targeted toward cooling the plant than for photosynthesis.
When this happens less sugar is produced and nutrient elements(Ca) transported
are less directed to the fruit but to the leaf where maximum transpiration occurs.
3.
Ammonium fertilization: When ammonium is
applied, it is converted amine and then to amino acids in the root. This requires
a lot of energy, therefore more sugar is needed and more chlorophyll produced.
The increase in photosynthesis results in increase plant root activity and leaf
function ( increase in root temperature, water transport, respiration and
ammonium metabolism). The sugar in the root is dependent on transport from the
leaf. When root temperature increases, root respiration also increases and
consumes sugar in parallel but independent
of N metabolism. These two processes, respiration and Ammonium
metabolism strongly compete for sugar in the root. When sugar is totally
consumed by respiration, ammonia production during ammonium metabolism becomes
very toxic to cell organs and impairs root growth and results in death of the
cell. When this happens especially in warm climates, more sugars are
accumulated in the leaves, high transpiration rates results and plants absorb
enough water for cooling purposes than for sugar production and translocation
due to death of root cell. The blossom end rot occurs as a result of the
developing fruits being deprived of sugar and water
4.
Excessive pruning: Pruning is the removal some
portions of the plant: root, shoots, leaves, flowers or fruits. The optimal and timely removal of these parts
has positive results on plant development and yield. Where these removals are
excessive and out of time could equally result in drastic result of which one
is blossom end rot. If excessive root pruning is done, it implies that the
number of roots that have been transporting water to balance the lost had been
reduced. As plants grow, they must
develop both roots and canopy in the right proportion in order to be in
balance. If a plant grows too many leaves before it establishes a strong root
system the excessive water loss cause the plant to die resulting from the being
unable to supply enough water. The other way round is also true when plants
have excessive roots that absorb more water than the leaves can lose, it causes
stress to the plant especially the fruits. Excessive transpiration makes plant
direct water in cooling purposes than for sugar production. Hence the fruits
are deprived of water and sugar resulting in blossom end rot.
Written by
Nolbert Poncian
(extension 0fficer)
Leave a Comment