Crop Physiology PDF

CROP PHYSIOLOGY Prepared and Compiled By: ROJIE C. ESPELITA Lecturer I Introduction  The spectacular diversity of plant size and form is familiar to everyone.  In nature all plants carry out similar physiological processes.  As primary producers, plants conver...

CROP PHYSIOLOGY Prepared and Compiled By: ROJIE C. ESPELITA Lecturer I Introduction  The spectacular diversity of plant size and form is familiar to everyone.  In nature all plants carry out similar physiological processes.  As primary producers, plants convert solar energy to chemical energy.  Being non motile, plants must grow toward light, and they must have efficient vascular systems for movement of water, mineral nutrients, and photosynthetic products throughout the plant body. Green land plants must also have mechanisms for avoiding desiccation.  Plant Physiology refers to “the science of properties and functions in normal conditions”. Aim of Plant Physiology has been describe: ___V.I. Palladin, Russian Plant Physiologyist early 20th Century___ “Which is to gain a complete and thorough knowledge of all the Phenomena occurring in plants, to analyse complex life processes. So as to interpret them in terms of simpler one and reduce them finally to the principles of physics and chemistry”. - Aim of Plant Physiology : History ___Noggle and fritz (1983)___described the Plant Physiology as: “the science concerned with processes and functions, the response of plants to changes in environment and the growth and development that results from responses” W.L. Balls (1915): Crop physiology, with the aim of understanding the dynamics of yield development in crops, Along with Holton he analysed the effects of plant spacing and sowing date on the development and yield of Egyptian Cotton plants within crop stands  1924- In England- a 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. 1950’s: Studies on photosynthetic rate of the leaf and the loss of photosynthates by respiration was studied by the development of ‘Infra Red Gas Analysis (IRGA)’method.  1953: Monsi and Saeki explained about 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.  Crop physiology is concerned with the processes and functions of the crops at cellular, sub-cellular and whole plant levels in response to environmental variables and growth. In short, physiology is the study of functional aspects of crop plants. Importance of crop physiology in agriculture:  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 of 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 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. Optimum seedling growth and plant population By knowing the process of radicle and plumule emergence and their function we can achieve best plant health, which is the outcome of best plant physiology. By knowing the different inputs requirement of plants (water, nutrients, sunlight) we can easily manage the plant population to get highest yield. Input interaction of plants within their body is the matter of plant physiology.  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).  Harvest index The difference between 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.  Mode of action of different weedicides The use of herbicides to kill unwanted plants is widespread in modern agriculture. Majority of Herbicides -about half of the commercially important compounds—act by interrupting photosynthetic electron flow.  Nutriophysiology Nutriophysiology is yet another important area to under stand crop physiology. For the healthy growth of a crop around 17 essential elements are required. Knowledge of nutriophysiology has helped in identification of essential nutrients, ion uptake mechanisms, their deficiency symptoms and corrective measures. It also helps to check the toxicity symptoms of various nutrients.  Photoperiodism Response of plant to the relative length of day and night is called as photoperiodism. This concept was used to choose photo insensitive varieties.  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.  Chapter-2 Plant cell: an Overview  Plants are multicellular organisms composed of Cell millions of cells with specialized functions. At maturity, such specialized cells may differ greatly from one another in their structures. However, all plant cells have the same basic eukaryotic organization: They contain a nucleus, a cytoplasm, and sub cellular organelles, and they are enclosed in a membrane that defines their boundaries.  In plants, cell migrations are prevented because each walled cell and its neighbor are cemented together by a middle lamella. As a consequence, plant development unlike animal development, depends solely on patterns of cell division and cell enlargement. There are two categories of seed plants,  Gymnosperms are the less advanced type.  Angiosperms, the more advanced type of seed plant which dominate the landscape. About 300,000 species are known, but many more remain to be characterized. The major innovation of the angiosperms is the flower; hence they are referred to as flowering plants.  Three major tissue systems are found in flowering plants; (all plant organs contain)  dermal tissue,- covers and protects the plants (barks)  ground tissue,- site for photosynthesis (leaves)  vascular tissue- transport water, minerals and sugar to different parts of the plants  The vegetative body of plants is composed of three organs leaf, stem, root.  Leaves are attached to the stem at nodes, and the region of the stem between two nodes is termed the internode. The stem together with its leaves is commonly referred to as the shoot.  Plant growth is concentrated in localized regions of cell division called meristems. Nearly all nuclear divisions (mitosis) and cell divisions (cytokinesis) occur in these meristematic regions. In a young plant, the most active meristems are called apical meristems; they are located at the tips of the stem and the root QUESTIONS?? Assignment/ Activity: In an A4 size coupon bond:  Draw the plant cell;  Identify its parts/organ and its functions.  Submission: on or before next meeting.