质体是细胞器，其主要在营养合成和生物分子的储存中起作用。虽然有不同类型的质体专门用于填补特定的作用，但质体具有一些共同的特征。它们位于细胞质中，被双脂膜包围。质体也有自己的DNA，可以独立于细胞的其他部分进行复制。一些质体含有色素并且色彩丰富，而其他质粒缺乏色素并且是无色的。质体从未成熟的未分化细胞发育，称为proplastids。 Proplastids成熟为四种类型的专门质体：叶绿体，色素体，gerontoplasts和leucoplast。老生殖细胞：这些质体是由叶绿体的降解产生的，叶绿体在植物细胞死亡时发生。在该过程中，叶绿素在叶绿体中被分解，在所得的生殖细胞中仅留下类胡萝卜素色素。 Leucoplasts：这些质体缺乏颜色和功能来储存营养。叶绿体：这些绿色质体通过葡萄糖合成负责光合作用和能量产生。它们含有叶绿素，一种吸收光能的绿色色素。叶绿体常见于位于植物叶和茎中的称为保卫细胞的特化细胞中。保护细胞打开和关闭称为气孔的微小孔隙，以允许光合作用所需的气体交换。
Plastids are organelles that function primarily in nutrient synthesis and storage of biological molecules. While there are different types of plastids specialized to fill specific roles, plastids share some common characteristics. They are located in the cell cytoplasm and are surrounded by a double lipid membrane. Plastids also have their own DNA and can replicate independently from the rest of the cell. Some plastids contain pigments and are colorful, while others lack pigments and are colorless. Plastids develop from immature, undifferentiated cells called proplastids. Proplastids mature into four types of specialized plastids: chloroplasts, chromoplasts, gerontoplasts, and leucoplasts. Gerontoplasts: These plastids develop from the degradation of chloroplasts, which occurs when plant cells die. In the process, chlorophyll is broken down in chloroplasts leaving only cartotenoid pigments in the resulting gerontoplast cells. Leucoplasts: These plastids lack color and function to store nutrients. Chloroplasts: These green plastids are responsible for photosynthesis and energy production through glucose synthesis. They contain chlorophyll, a green pigment that absorbs light energy. Chloroplasts are commonly found in specialized cells called guard cells located in plant leaves and stems. Guard cells open and close tiny pores called stomata to allow for gas exchange required for photosynthesis. Chromoplasts: These colorful plastids are responsible for cartenoid pigment production and storage. Carotenoids produce red, yellow, and orange pigments. Chromoplasts are primarily located in ripened fruit, flowers, roots, and leaves of angiosperms. They are responsible for tissue coloration in plants, which serves to attract pollinators. Some chloroplasts found in unripened fruit convert to chromoplasts as the fruit matures. This change of color from green to a carotenoid color indicates that the fruit is ripe. Leaf color change in fall is due to loss of the green pigment chlorophyll, which reveals the underlying carotenoid coloration of the leaves. Amyloplasts can also be converted to chromoplasts by first transitioning to amylochromoplasts (plastids containing starch and carotenoids) and then to chromoplasts.