Fundamentals of Crop Physiology PDF HD Format Notes in Hindi /English
The Genetic potential of a plant and its interaction with environmental factors decides its growth and development by influencing or modifying certain internal processes. Plant physiology studies these internal processes and their functional aspects. Plant physiology is the study of Vital phenomena in plants.
It is the science concerned with Processes and functions, the responses of plants to the environment, and the growth and development that result from the responses. It helps to understand various biological processes of the plants like Photosynthesis, respiration, transpiration, translocation, nutrient uptake, plant growth regulation through hormones, and other processes that have a profound impact on crop yield.
Also the importance of Crop Physiology in Agriculture 2024 Check All Details
Fundamentals of Crop Physiology PDF HD Format Notes download below
1. Processes :
Processes mean natural events/sequences of events. Examples of processes that occur in living plants are
♦ Photosynthesis ♦ Respiration
♦ Ion absorption ♦ Translocation
♦ Transpiration ♦ Stomatal opening and closing
♦ Assimilation ♦ Flowering
♦ Seed formation and ♦ Seed germination
Describing and explaining the plant processes is the main task or the first task of plant physiology.
Function means the natural activity of a cell or tissue, organ, or chemical substance. So, the second task of plant physiology is to describe and explain the function of an organ, tissue, cell, and cell organelle in plants and the function of each chemical constituent, whether it may be an ion, molecule, or macromolecule.
Both processes and functions are dependent on external factors and are modified by external factors such as light and temperature. Since these two factors are modified by external factors, the third task of plant physiology is to describe and explain how processes and functions respond to changes in the environment.
Essentially the overall goal of plant physiology is to evolve a detailed and comprehensive knowledge of all the natural phenomena that occur in living plants and thus to understand the nature of plant growth, development, and productivity. Many aspects of practical agriculture can benefit from more intensive research in plant physiology.
Crop: it is a group of plants grown as a community in a specific locality and, for a specific purpose.
Crop Physiology :
Crop physiology is the study of how plant physiological processes are integrated to cause whole plant responses in communities. The subject matter of crop physiology includes how the knowledge of plant physiology is applied for better management of crops.
A brief history of Crop Physiology:
W.L. Balls (1915): Crop physiology, to understand the dynamics of yield development in crops, really began with the work of W.L. Balls. Along with Holton, he analyzed the effects of plant spacing and sowing date on the development and yield of Egyptian Cotton plants within crop stands, not in isolated plants. It was from his work the term ‘crop physiology’ came into existence. From then onwards, various scientists have started applying the advances in physiological knowledge for better crop management.
1924- In England- rapid development of the methods of growth and yield analysis by different investigators (V.H. Blackman, F.G. Gregory, G.E. Briggs, etc.) was started. With the development of various methods of growth analysis, they started explaining ‘the physiology of crop yield’.
1947: The concept of LAI (Leaf area index) was developed by D.J. Watson. This index has provided a more meaningful way of analyzing growth in crops and stimulated renewed interest in crop physiology. 1950s: Studies on the photosynthetic rate of the leaf and the loss of photosynthates by respiration were studied by the development of the ‘Infra Red Gas Analysis (IRGA)’ method. This method has facilitated the estimation of short-term rates of Photosynthesis and respiration by crops in the field.
1953: Monsi and Saeki explained the manner of light interception by the crop canopy with their concept of light interception coefficient.
1963: Hesketh and Moss showed that photosynthesis by leaves of Maize, Sugarcane and related tropical grasses could reach much higher rates, with less marked light saturation, than leaves of other plants. (This was the starting point for research to find other photosynthetic CO2 fixation pathways like C4, and CAM Mechanisms). The differences in the pathway are associated with differences in photosynthetic rate, in response to light intensity, temperature, and oxygen level, in photorespiration, leaf anatomy, and chloroplast morphology, in the rate of translocation, and in the efficiency of water use, which can have profound effects on the physiology of yield determination.
Later on, several research works were carried out to understand the processes like translocation of food materials, their partitioning towards economic yield, storage mechanisms, physiology of flowering, the effect of stressful environmental factors on crop growth and development, the role of plant growth regulators in increasing the crop productivity, etc. All these areas have enriched the knowledge of physiological processes and their role in deciding crop yield.
Importance of crop physiology in agriculture:
Many aspects of Agriculture and Horticulture can benefit from more intensive research in plant physiology to provide practical solutions in agriculture and horticulture. Understanding the physiological aspects of seed germination, seedling growth, crop establishment, vegetative development, flowering, fruit and seed setting and crop maturity, plant hormone interaction, nutrient physiology, stress (biotic/abiotic) physiology, etc., provides a reasonable scientific base for effective monitoring and beneficial manipulation of these phenomena. Since in agriculture, we are interested in economic yield which is the output of these phenomena, and well beingness of plants, Plant Physiology provides a platform for getting a better yield of crops.
Studying this phenomenon to develop better crop management practices forms the subject matter of crop physiology. The importance of physiology in agriculture and horticulture can be seen in the following examples;
1. Seed Physiology.
Seed is the most important input in agriculture. Germination of seed and proper establishment of seedling depends upon various internal and external factors. Knowledge of Seed physiology helps in understanding different physiological and morphological changes that occur during germination. Any deviation in these processes causes Seed dormancy. The dormant condition of the seed bars immediate use of harvested seed for the next crop which is important in intensive agriculture. By understanding the causes and effects of this problem, Crop physiologists have come up with different methods of breaking the seed dormancy. Example: Whenever Paddy is used as a seed material in the very next season it is recommended to treat the seed either with HNO3 or with GA.
2. Optimum seedling growth and plant population.
By knowing the process of radicle and plumule emergence and their function we can achieve the best plant health, which is the outcome of the best plant physiology. By knowing the different input requirements of plants (water, nutrients, sunlight) we can easily manage the plant population to get the highest yield. Input interaction of plants within their body is a matter of plant physiology.
3. Growth measurement of crops.
The first prerequisite for higher yields in crops is high total dry matter production per unit area. High dry matter production is a function of optimum leaf area (Optimum leaf area Index) and Net Assimilation rate. (CGR = LAI X NAR). Example: Pruning operation in horticultural crops like Mango is done based on this principle of proper canopy management for better photosynthesis.
4. Harvest index.
The difference between the total amount of dry matter produced and the photosynthates used in respiration is the net product of photosynthesis. Economic yield depends on how the dry matter is distributed among different organs of the plant. Partition of total dry matter amongst the major plant organs is of interest to the farmers as they are more interested in its partition towards economic yield. Example: excessive vegetative growth period in Ground nut produces less number of Pods as the reproductive period gets constricted. Thus, groundnut varieties with relatively extended periods of reproductive growth are desirable.
5. Mode of action of different weedicides.
The use of herbicides to kill unwanted plants is widespread in modern agriculture. The majority of Herbicides -about half of the commercially important compounds—act by interrupting photosynthetic electron flow (Ex. Paraquat, diuron) or electron flow of respiration. In Photosynthesis when the electron transport is blocked, it virtually stops the light reaction of photosynthesis. When the light reaction is stopped the dark reaction does not happen and thus CO2 is not fixed as a carbohydrate. Therefore, the weed is killed by starvation.
Neurophysiology is yet another important area to understand crop physiology. For the healthy growth of a crop around 17 essential elements are required. Knowledge of nutriophysiology has helped in the identification of essential nutrients, ion uptake mechanisms, their deficiency symptoms, and corrective measures. It also helps to check the toxicity symptoms of various nutrients. The use of fertilizers and their intake by plants can be understood by studying plant physiology.
The response of plants to the relative length of day and night is called photoperiodism. This concept was used to choose photo-insensitive varieties. The semi-dwarf Rice varieties that have revolutionized Indian agriculture, are lodging resistant, fertilizer responsive, high yielding, and photo insensitive. Photo insensitivity has allowed rice cultivation in nontraditional areas like Punjab. Even in traditional areas, rice-wheat rotation has become possible only due to these varieties.
8. Plant growth regulators.
Plants can regulate their growth through internal growth mechanisms involving the action of extremely low concentrations of chemical substances called Plant growth substances, phytohormones, or Plant growth regulators. The regulation of flowering, seed formation, and fruit setting has been controlled through the application of different hormones at the appropriate time of plant height and age.
9. Indian agriculture is predominantly rainfed in nature.
So the development of drought-resistant varieties is very important. Root zone depth, density of roots, plant water potential, relative water content, water use efficiency, and xerophytic characteristics of leaves, etc. are some of the characters helped to breed drought-tolerant varieties and to develop efficient irrigation management practices (sprinkler and drip irrigation).
10. Among Several physiological approaches,
Transpiration efficiency or water use efficiency is the most dependable trait, which is “the amount of dry matter produced per unit amount of water transpired”. The importance of water use efficiency (WUE) in influencing grain yield under water-limited conditions can be explained by the following model given by Passioura.
Grain Yield = T x TE x HI
Where T = Total transpiration by the crop canopy
TE = Transpiration Efficiency or WUE
HI = Harvest Index (Economic Fraction of Dry matter)
This relationship provides an analytical tool to select the genotype with high levels of
T and TE.
11. Post-harvest Physiology.
Post-harvest losses in agriculture and horticulture are causing great distress to the farming community. Moisture and temperature are the two important factors causing physiological changes that reduce the post-harvest quality of grains. Control of moisture content and maintenance of low temperatures have proved effective in the storage of grains. Being perishable the magnitude of post-harvest loss is comparatively higher in horticultural crops. Example: In recent years a method called ‘modified atmospheric storage’ was developed for prolonged post-harvest life of fruits and vegetables. The shelf life of cut flowers can be increased by application of kinetin (cytokinin). This will reduce the burst of ethylene and thus reduce the rate of senescence.
Thus, a physiological understanding of crop plants provides the fundamental scientific base for various aspects of metabolism, growth, and development. This is immensely important for crop improvement or technology improvement in agriculture or horticulture