A plant that was given to me as a cutting has clear beads at irregular intervals along the stem. They are firm rather than sticky, but can be mashed between thumbnails. Is this insect- or disease-related, or something else? (The plant may be Abutilon but it has not flowered yet, so I am not sure.)
It is possible that these are ‘pearl bodies‘, also called ‘pearl glands’ or–if seen on grapes–‘grape balls.’ According to this scientific article, they are a type of food body (a nutrient-dense plant structure that offers food rewards to creatures such as ants). Other types of food bodies are extrafloral nectaries that secrete nectar, and domatia (chambers a plant produces to house ants or mites). Pearl bodies are part of a system of mutualism between plant and arthropod: ants gather the pearl bodies and take them to their nests, prompting the plant to form new ones in their place; in return, the ants may defend the plants against insect pests. Pearl bodies may be found on many different plants, particularly on a plant’s most robust branches.