HORTICULTURE

Detailed explanation-1: -(A) Aphids penetrate the plant with their stylet and move it through the apoplast toward the sieve tubes.

Detailed explanation-2: -By feeding on the phloem, aphids obtain the amino acids they need. The phloem is poor in some of the essential amino acids but aphids have symbiotic bacteria (Buchnera) that can upgrade non-essential amino acids into essential ones.

Detailed explanation-3: -Aphids possess a protruding mouthpiece (called a stylet), which pierces the plant’s sieve tube to allow sap to be extracted. The penetration of the stylet into the sieve tube is aided by digestive enzymes that soften the intervening tissue layers.

Detailed explanation-4: -Prior to feeding, the aphid stylet must penetrate the plant epidermis and move through the cortical layer. To facilitate this process, aphids secrete gel saliva which hardens to form a surface flange and a continuous tubular sheath encasing the full length of the stylet within the apoplast.

Detailed explanation-5: -Aphids pierce the tissues of plants with their tubular mouthparts and suck out the phloem juices. Because this food is mostly sugar water with a low concentration of protein, the aphids have to process large volumes of it to obtain sufficient protein.