Understanding Plants & their Needs

The beginners often ask questions like – “How often, how much & when shall I water the plant?” “Why the seeds I sow fail to sprout?” “I bought a healthy plant in full bloom from a nursery. Though I followed all the instructions given by the nurseryman, the plant never bloomed again; what went wrong?” For every such problem different experts will offer different solutions; which are often contradictory to each other. This confuses the beginner most. Gardening books do not help much; as they give only general information and problem faced by a beginner are innumerable and peculiar. No book could ever cover all the aspects and fineries of gardening.

How then a beginner is to overcome these hurdles? There is a way out of this. A few things required to be a successful gardener are as follows:

  1. Intense love for plants and nature
  2. Keen sense of observation
  3. Patience and initiative to experiment
  4. Basic knowledge of plant life.

Having first three points to your credit, you can still be a successful gardener. The knowledge of plant life will come to you without your knowing it. But, a beginner will attain success much faster if he/she is conversant with various functions carried out by different parts of a plant. The object of this course is to give the basic knowledge of gardening as a hobby and to enable a person to achieve confidence to find his/her own solutions to problems he faces.

To understand plants, we must know function of each part of a plant. So, instead of studying the plant as a whole, let us find different functions carried out by various parts of a plant.

Roots : Give support to a plant. Absorb water and water-soluble minerals. Roots of some plants also serve as storehouses of food produced by plants themselves. Only young roots and hair roots are capable of active absorption of water and water-soluble minerals. The roots need air for healthy growth. That is why if water stagnates around the roots, they get suffocated and then die. If the roots die, then in spite of having so much water around them, they still cannot absorb it. Thus the plant wilts. This type of wilting is called as ‘wet wilt’. Most leguminous plants have nodules on their roots, which shelter nitrogen-fixing bacteria. This helps not only the leguminous plants themselves but also helps in enriching the soil.

Stems : Provide support to other parts of a plant. Water, nutrients, food and hormones are transported to different parts through the stem. The canals located in woody parts of a stem are called ‘xylem’, which carry water and minerals dissolved in water. ‘Phloem’ the other canals located between xylem and outer skin, transport food and hormones. The movement of water and minerals is upwards, from roots to other parts. Food manufactured mostly in leaves and other green parts of the stem and also the hormones are transported through phloem. The direction of this movement is normally downwards. Stems too respire.

Leaves : Three main processes which go in leaves are ‘photosynthesis’, ‘respiration’ and transpiration. All these processes, in which exchange of gases or water vapour play a part take place through pores. Pores, the tiny openings, mostly located on the underside of the leaf are capable of absorbing air and water-soluble minerals or other chemicals, such as insecticides.

leaf stoma diagram

Photosynthesis : Leaves manufacture food from two basic raw materials – water and carbon dioxide. This process is called as ‘photosynthesis’. To convert these two raw materials in to sugars – the basic plant food, plants need energy. This energy is provided by the sunlight. In presence of green chlorophyll in the leaves and by using the energy of sunlight, plants convert carbon dioxide and water in to food. The food manufactured so is used by the plant for its growth and for maintenance. In the process of photosynthesis, oxygen is released as a byproduct through pores in to atmosphere. In nature, as the sunlight is available only at daytime, Photosynthesis takes place only as long as sunlight is available. The excess food is often stored as surplus, commonly as starch, in roots or stems. The plant rarely uses food so stored again. Plants if defoliated very often will starve to death. As leaves manufacture food, it is always beneficial to retain at least a few leaves on stem cuttings used for propagation.

Respiration : Plants need oxygen for the process of respiration. In this process of respiration, oxygen diffused through leaf pores reaches the cells. Within a cell, in controlled condition, oxidation of sugars (plant food) takes place. In this process the energy is liberated, which is needed for the maintenance and growth of a plant. In this process carbon dioxide and water vapour are released through pores as byproducts. Respiration takes place day and night. In daytime not only the carbon dioxide released as a byproduct is re-used in photosynthesis, but, also a great quantity of atmospheric carbon dioxide is also consumed. Thus plants help in purifying atmospheric air.

Transpiration : We know that a wet cloth dries in air. As air is drier than the wet cloth, air absorbs moisture from the cloth, as a result of which the cloth dries. Similarly, in transpiration, drier atmospheric air absorbs the moisture of the leaves through the leaf pores. Thus leaves constantly lose moisture through the pores. However, as a result, leaves do not wilt; because the roots constantly replenish the water supply. But if enough water is not available near the roots, more moisture is lost; which causes the wilt in the plant.

In a bottle garden plants remain alive for very long duration only because of the three above mentioned functions which take place in plants.

Photosynthesis, Respiration & Transpiration Comparison
Occurs only in green cells Occurs in every active, living cell Occurs in every active, living cell
Takes place only in presence of light Takes place during light & dark Takes place during light & dark
Uses water & carbon dioxide Uses food & oxygen Water evaporates in to atmosphere
Releases oxygen Releases water vapour & carbon dioxide
Solar energy is converted into chemical energy Chemical energy is converted into heat & useful energy
Results in increase in weight Results in decrease in weight
Food is produced Food is broken down

Flowers : Sexual reproduction gives rise to seeds in a plant. Seed production upon which the very survival of not only plants but even animals and human beings depends.

A flower is composed of a number of organs. Only two of these, stamens (male sexual parts) and pistils (female sexual parts) are directly concerned with sexual reproduction. Pollen grains released from stamens pollinate the stigma (receptive portion of pistils) and cause fertilization of ovules.

Bisexual flowers have both stamens and pistils. Example – rose, hibiscus. However, unisexual flowers are those flowers, which have either only stamens or only pistils. Such flowers are called staminate (male) or pistillate (female) flowers respectively. There are certain plants on which both staminate & pistillate flowers may be present on the same plant, Example – Cucumber, corn, coconut palm. In this case, though the flowers are unisexual, the plant is said to be bisexual. In some plants staminate and pistillate flowers occur on different plants of the same species. Examples – Date palm, Tadgola palm, Aamsul, Jayphal etc.

Symptoms of Under Watering : Shrunken or dried leaves and stems. Dried leaves remain on the plant and do not fall off easily. The symptoms start from the growing tip of the plant and spread downwards.

Symptoms of Over Watering : Leaves start to turn yellowish. Such leaves easily fall down. The rot starts near the root and spreads upwards. Succulent and herbaceous plants will suddenly turn to pulp. In some cases of woody plants, if the roots rot, the upper portion is starved of water. This may indicate the symptoms of under watering, but if one is observant, it is not difficult to distinguish the difference. This type of wilting is called “wet wilt”.

Symptoms of Excessive Sunlight : Shade loving plants if exposed to harsh sunlight will show burnt, brown patches on the leaves. The upper leaves are affected more, as lower leaves get some protection of the upper leaves. The brown patches turn paper-dry.

Symptoms of Lack Of Sunlight : The dense growth of the plant will disappear and the plants will grow lanky. Coloured leaves will loose their colour and start turning pale green. Green leaves will start turning yellow. Fleshy leaves will start turning thin. Certain plants, which have hairy growth on leaves & stems, will start getting hairless.