Morphometric analysis of young petiole galls on the narrow-leaf cottonwood, Populus angustifolia, by the sugarbeet root aphid, Pemphigus betae.

An insect-induced gall is a highly specialized structure resulting from atypical development of plant tissue induced by a reaction to the presence and activity of an insect. The insect induces a differentiation of tissues with features and functions of an ectopic organ, providing nutrition and protection to the galling insect from natural enemies and environmental stresses. In this anatomical and cytological study, we characterized how the gall-inducing aphid Pemphigus betae reshapes the leaf morphology of the narrow-leaf cottonwood Populus angustifolia to form a leaf fold gall. Young galls displayed a bend on one side of the midvein toward the center of the leaf and back to create a fold on the abaxial side of the leaf. This fold was formed abaxially by periclinal and anticlinal divisions, effectively eliminating intercellular spaces from the spongy parenchyma. Galls at this stage exhibited both cell hypertrophy and tissue hyperplasia. Cells on the adaxial surface were more numerous and smaller than cells near the abaxial surface were, creating the large fold that surrounds the insect. Mesophyll cells exhibited some features typical of nutritive cells induced by other galling insects, including conspicuous nucleolus, reduced and fragmented vacuole, smaller and degraded chloroplasts, and dense cytoplasm compared to ungalled tissue. Even though aphids feed on the contents of phloem and do not directly consume the gall tissue, they induce changes in the plant vascular system, which lead to nutrient accumulation to support the growing aphid numbers in mature galls.

Descriptive sensory analysis and free sugar contents of chestnut cultivars grown in North America.

BACKGROUND: Various chestnut (Castanea) species and cultivars are currently produced and marketed in North America including Peach, Qing, AU-Homestead, Eaton, Marrone di Castel del Rio, and Colossal. In spite of their availability in the marketplace, similarities in sensory characteristics of chestnuts, as well as their unique attributes, have not been explored. Therefore, the objectives of this study were to evaluate texture and flavor attributes of commonly grown chestnut cultivars using descriptive sensory analysis and to quantify their free sugar content by gas-liquid chromatography. RESULTS: Twenty-three sensory terms were used for descriptive analysis of roasted chestnuts. All but two attributes (raw impression and fermented) were common to all chestnut cultivars. Peelability, initial firmness, dissolvability, and mustard, sweet, and sour flavors varied among cultivars. Sucrose, the predominant free sugar in chestnuts, was greatest in Colossal chestnuts from California, while those of Peach had the lowest content. Glucose, fructose and maltose were also present in chestnuts. CONCLUSION: This study demonstrated that cultivars of various chestnut species share several common sensory attributes, but differ in intensity ratings of six descriptors. Of these attributes, sweetness has been associated with consumer acceptance and can be promoted in the marketplace.