Waiting for spring

Pollen waiting for spring in january 2014... more

by Leif Sohlman

Title

Waiting for spring

Artist

Leif Sohlman

Medium

Photograph - Photo

Description

pollen waiting for spring in january 2014
Canon 5D mk III
Pollen is a fine to coarse powder containing the microgametophytes of seed plants, which produce the male gametes (sperm cells). Pollen grains have a hard coat that protects the sperm cells during the process of their movement from the stamens to the pistil of flowering plants or from the male cone to the female cone of coniferous plants. When pollen lands on a compatible pistil or female cone (i.e., when pollination has occurred), it germinates and produces a pollen tube that transfers the sperm to the ovule (containing the female gametophyte). Individual pollen grains are small enough to require magnification to see detail. The study of pollen is called palynology and is highly useful in paleoecology, paleontology, archeology, and forensics
A Russian theoretical biologist has suggested that the quantity of pollen reaching a pistillate flower can transmit ecological information and also regulate evolutionary plasticity in cross-pollinating plants. Plentiful pollen indicates optimum environmental conditions (for example a plant that is situated at the center of its natural range, in ideal growing conditions, with a large number of male plants nearby, and favorable weather conditions), whereas a small amount of pollen indicates extreme conditions (at the borders of its range, with a deficiency of male plants, and adverse weather conditions). Geodakyan believes that the quantity of pollen reaching a pistillate flower defines the sex ratio, dispersion and sexual dimorphism of a plant population. High pollen quantity leads to a reduction of these characteristics and stabilization of a population. Small quantity leads to their increase and destabilization of a population.[8]

Dependence of the secondary sex ratio on the amount of fertilizing pollen was confirmed on four dioecious plant species from three families � Rumex acetosa (Polygonaceae),[9][10] Melandrium album (Cariophyllaceae),[11][12] Cannabis sativa[13] and Humulus japonicus (Cannabinaceae).[14] (see summary of all these data in review article).[15]

Dependence of offspring phenotype variety on amount of pollen was observed by Ter-Avanesyan in 1949. All three studied species of plants (cotton plant, black-eyed pea, and wheat) showed dependence in the direction forecast by the theory � fertilization with a small amount of pollen resulted in an increase in the diversity of the offspring. Ter-Avanesian writes that as a result of a limited pollination, "instead of homogenous sorts we get populations".[

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Uploaded

January 22nd, 2014