#27 - Apr 2016 - Garden Stuff - © Sandy Lang - slang@xtra.co.nz SEX April/May: Mid/late autumn. Shorter days, less photosynthesis. Cooler, less growth. Sex: Time we had that little talk. About 4 billion years ago, nature produced the first life forms, prokaryotes (cells with no organelles). About 2 billion years ago, it produced the eukaryotes (cells with organelles). We are eukaryotes, as are most other living things today. After the prokaryotes and before the eukaryotes, nature invented sex. Almost all living things now reproduce sexually. What’s so great about sex? When a new seed or baby (etc) arrives, it has an equal share of the genes of each parent. We have ~20,000 genes, so each baby has ~10,000 ‘mum’ genes and ~10,000 ‘dad’ genes (total ~20,000). But no two babies are the same because each gained a different, random, selection of parental genes. In a challenging world, diversity ensures some will thrive, almost whatever happens. So, sex drives diversity and diversity drives adaptation and survival. Odds: Apples have ~10 seeds. Plant these and you get 10 different trees, each bearing fruit of different quality. Most will revert to wild-type (small, sour). An apple breeder plants 1,000 seeds, then spends years finding the 1 ‘elite’ tree and culling the 999 ‘mediocre’ trees. The odds of an elite tree are ~1 in 1,000. Elites: Growers (apples, kiwifruit, grapes, forests…) always plant genetically-identical, elite, named, varieties (propagated by cuttings, grafting etc). Why spend years growing a tree from seed, then find its fruit are inedible? Same with harvesting veggie seeds for next year. Fun, maybe, but wise, not very. Buy new seeds. You get what’s on the pack. Sexually incompatible: Most plants produce both male and female parts. But, so the advantages of sex are not lost, they are usually sexually ‘self-incompatible’ (they can’t fertilise themselves). So, a fruit tree requires pollen from a different variety. Growers plant sexually compatible varieties together. For a small garden, buy a tree with two/three sexually compatible varieties grafted on one trunk. No insects, no sex, no seeds, no hormones, no fruit: •Insects transfer pollen, tree to tree (no insects=no sex). •A seed results when an ovule is fertilised by a pollen grain (no sex=no seed). •Seeds produce growth hormones (no seeds=no hormones). •It’s rare you get a seedless fruit because seed hormones drive fruit growth (no hormones=no growth). In most fruits (grapes, apples, kiwifruit, tomatoes…) more insects=more sex=more seeds=more hormones=bigger fruit. ___________________________________