PINACEAE

A Typical Pollen Grain
Pinaceae is the largest and most important family of Gymnosperms; the plants of this family have evergreen, needlelike or linear leaves arranged in spirals or fascicle with flattened cone scale distinct from the subtending bract. The mature cones are woody, seeds winged or wingless. There are six genera of this family found primarily in North America i.e. Abies, Larix, Picea, Pinus, Pseudotsuga and Tsuga. Abundant pollen grains are produced in the spring and early summer.
Pollen grain consisting of a body with two laterally placed bladders (sacca, vesicles). Its maximum dimension is generally 50 - 75 µm. Two pine subgenera Haploxylon and Diploxylon are differentiated by the presence or absence of bumps. The outer junction between the body and the bladder is acute, except a few species.
Allergenicity 

Rarely it causes pollinosis (an allergic reaction (hay fever) resulting in a type I antibody-mediated hypersensitivity). Infrequent reports of pollen allergenicity generally at low levels of sensitivity are known from California, Colorado, Alabama, Connecticut and Florida.
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