question_answer 51)

  Is there a species specific or region specific type of plastids? How does one distinguish one from the other?

Answer:

                  Plastids are species specific and are found in all plant cells and in euglenoids. They bear some specific pigments thus, imparting specific colours to the part of the plant whichpossess them. Based on the type of pigments plastids are classified into three main types ,i'.e., leucoplasts, chromoplasts and chloroplasts.Leucoplasts They are colourless plastids which store food material based on there storageproducts, they are of three types (a)    Amyloplasts Stores starch, e.g., tuber of potato, grain of rice, grain of wheat. (b)Elaioplasts These store fats, e.g., rose (c)Aleuroplasts They are protein storing plastids, e.g., castor endosperm Chromoplast These are non photosynthetic coloured plastids which synthesise and store carotenoid pigments. They appear orange, red or yellow. These mostly occur in ripe fruits(tomato and chilles) carrot roots, etc.  ChloroplastsThese are green colour plastids which help in synthesising food material byphotosynthesis. They contain chlorophyll and carotenoid pigments which trap light energy. Each chloroplast is oval or spherical, double membrane bound cell organelle. The space present inside inner membrane is called stroma. A number of organised flattened membranous sacs called thylakoids are present in the stroma. Thylakoids are arranged instacks are called grana. The thylakoids of different grana are connected by membranous tubules called the stromalamellae. The stroma of the lamellae contain the enzymes that are required for the synthesisof carbohydrates and proteins.