The Triumph of Seeds Read Online Free PDF Page B

careers, she and Jerry had decided they were just too busy to have children. In studying seeds, I now realized, they had nonetheless devoted themselves to the fickle lives of babies.
    The Baskins’ decades of work illustrate just how much there is to learn about what happens inside a germinating seed. Questions raised over 2,000 years ago by Theophrastus, “the father of botany,” continue to challenge scientists. As Aristotle’s student and successor, Theophrastus led exhaustive plant studies at the Lyceum, publishing books that remained definitive for centuries. Working on everything from chickpeas to frankincense, he described germination in great detail, wondering about seed longevity as well as differences “in the seeds themselves, in the ground, in the state of the atmosphere, and in theseason at which each is sown.” In the long years since, researchers have unraveled many of the processes guiding dormancy, awakening, and growth. It is well established that germinating seeds imbibe water and extend their roots and/or shoots through cell expansion. This stage is followed by rapid cell division fueled by the energy in their food reserves. But the exact cues that trigger and coordinate these events retain an aura of mystery.
    Germination chemistry alone involves a huge variety of reactions as the dormant metabolism comes to life, producing all the hormones, enzymes, and other compounds necessary to transform stored food into plant material. For avocados, that stored food includes everything from starch and protein to fatty oils and pure sugar—a mixture so rich that nurseries don’t even bother withfertilizers until well beyond the seedling stage. Transferring my young trees to potting soil, I noticed their cotyledons still clinging to the bases of the stems like pairs of upraised hands. Months or even years after rooting and leafing out, young avocado trees can still eke out a trickle of energy from the lunches their mothers packed. It’s no coincidence that an avocado endows its offspring so generously. Like almendros , avocados evolved to sprout in the deep shade of a rainforest, where light is scarce and where massive food reserves can give the seedlings a distinct advantage. Their story (and their seeds) would be entirely different if they had hailed from deserts or high mountain meadows, places where every young plant has a quick path to full sun.
    Seed strategies vary incredibly, their shapes and sizes adapted to every nuance of habitat on the planet. While this makes them a fascinating topic for a book, it can also make it hard to agree on just what part of a plant constitutes the seed. For purists, the seed includes only the seed coat and what lies within. Everything outside of that is fruit. In practice, however, seeds often co-opt fruit tissues for protection or other seed-like roles, and their structures become so fused that they’re difficult or impossible to distinguish. Even professional botanists often fall back on a more intuitive definition: the hard bit encompassing the baby plant. Or, even more simply: what a farmer sows to raise a crop. This functional approach equates a pine nut with a watermelon pip or a kernel of corn, avoiding technical distractions about the role of every plant tissue involved. It’s a model well suited to this book, but not without noting just how strangely different the contents of seeds can be.
    Because the products of evolution work so beautifully in practice, it’s easy to imagine the process chugging along like some grand assembly line, fitting each cog and sprocket to its particular place, for its particular function. But as any fan of Junkyard Wars , MacGyver , or Rube Goldberg devices knows, common objects can be reimagined and repurposed, and almost anything will work in a pinch. The sheer ceaselessness of natural selection’s trial and error means thatall sorts of adaptations are possible. A seed may be a baby in a box with its lunch, but plants have come