Pollen tube by recognition and hydration of the pollen that allows for germination of the tube and ultimate growth. In the pollen grain, the generative cell gives rise to the sperm, whereas the vegetative cells have a tube cell that grows the pollen tube. There is competition in this step as many pollen grains may compete to reach the egg. The stigma plays a role in guiding the sperm to a receptive ovule, in the case of many ovules. Only compatible pollen grains are allowed to grow as determined by signaling with the stigma. Some plants have mechanisms in place to prevent
Spore (agricultural publication) publisher, CTA. Recent Special Issues have covered Climate Change (2015), Family Farming (2014), Structured Grain Trading (2013); Agricultural Value Chains (2012); Modernizing Farms (2011) and Population and Agriculture (2010). Issues from September 1997 (No. 72) to the present are available at the magazine's website . Issues 1-69 are available from . Spore (agricultural publication) Spore is a magazine published by the Technical Centre for Agricultural and Rural Cooperation ACP-EU (CTA) in English and French. It covers a wide range of agricultural topics and is extensively distributed and widely reproduced throughout African, Caribbean and Pacific (ACP) countries and elsewhere. Originally known