Sap transport proteins. Recent evidence indicates that mobile proteins and RNA are part of the plant's long-distance communication signaling system. Evidence also exists for the directed transport and sorting of macromolecules as they pass through plasmodesmata." A large number of insects of the order Hemiptera (the half-wings), feed directly on phloem sap, and make it the primary component of their diet. Phloem sap is "nutrient-rich compared with many other plant products and generally lacking in toxins and feeding deterrents, [yet] it is consumed as the dominant or sole diet by a very restricted range of animals". This apparent paradox is explained
Plant tissue test such as N-deficiency. Research has shown the K step is able to measure N-stress. Plant tissue test The nutrient content of a plant can be assessed by testing a sample of tissue from that plant. These tests are important in agriculture since fertilizer application can be fine-tuned if the plants nutrient status is known. Nitrogen most commonly limits plant growth and is the most managed nutrient. Tissue tests are almost always useful, since they provides additional information about the physiology of the crop. Tissue tests are especially useful in certain situations; Traditional tissue tests are destructive tests where a sample