Seed germination

Some seed germinate easily; some are hard or tricky to get to germinate because of their dormancy. So why is it that all the species TPP works on are in the 2nd category? Seeds do this for a variety of reasons. If all a plant's seeds germinate readily and something happens to the entire crop, like a late freeze, a generation has been lost. Not so bad for a perennial. However having some seeds that are reluctant to germinate produces a seed bank where not all the seeds produced each season germinate so some remain for the next season. So even if pollination and seed production are terrible, some seedlings may appear from last year's seed. Seeds here in the temperate zone often need a cold period to promote germination, a process called vernalization. Some need alternating cold then warm periods. Some need to have their seed coats etched or softened by a trip through a digestive tract. But then some need to be begged and pleaded with, and still they fail to germinate or germinate a such a low rate as to be useless. What an annoyance! And you often try to imitate natural conditions figuring something out there worked, but there are a lot of variables and it takes considerable time and a lot of fiddling. Part of you wants to solve this problem, this riddle, but so much time has been invested already you just don't want to invest that much more. BTW, seedlings from the field don't like being transplanted either. No wonder so many people work on a stupid little mustard. 

Cracking seed germination

Let's put this bluntly; some seeds are just a bitch to germinate.  Once when using morning glories for an experiment, to get good germination all at once, the seeds were washed in concentrated sulfuric acid for a few minutes and then washed in water.  A good deal of the seed coat was dissolved, but the embryos within were undamaged and the seeds all germinated at once.  A lot of our temperate zone seeds need a cold period, often several cold periods, alternating with warmer periods to convince them that spring has sprung and they should germinate.  This is called vernalization.  Some seeds need considerable washing to remove germination inhibitors, a mechanism to assure germination just after sufficient rainfall.  Some prairie seeds actually germinate better after a fire.  In an effort to mimic a fire treatment in a safe and controlled manner, a student researcher took some difficult to germinate seeds (a legume), packaged them in little filter paper packets, constructed a lab-style double boiler, and steamed the packets for 4 mins.  They germinated like crazy after only a 1 week cold period!  Seeds collected from litter after an actual prairie fire also germinated OK, but not quite as well probably because some were cooked and some were not heated enough.  The untreated seed, no fire, no steam, just sat there week after week. The after-a-fire germination is a good strategy too because after a fire  because the accumulated dead plant material is removed so seedlings will get more sun and the ash is full of nutrients.  Now to try the steam heat method on a couple of other very stubborn seeds.   

Unusual tomato plants

OK, quick tomato growers quiz. What's wrong with these tomato plants? Nothing actually; they are normal enough tomato seeds sprouting normal enough tomato plants. What makes them unusual is that they are sprouting from inside an intact tomato fruit, and you don't see this happen very often.

Like many plants, seeds inside tomatoes are inhibited from germinating. Fleshy fruits function by attracting and rewarding animal seed dispersers, and they broadly fall into two categories: fruits with many small seed and fruits with few, large-seeds. The former get eaten with the fruit, pass through the GI tract unscathed, and get deposited in a nitrogen rich environment ready to grow. Some seeds actually require passage through the GI tract to readily germinate. The seeds are numerous enough that while a few get destroyed by chewing, the majority get swallowed intact. And the digestion process removes the inhibiting tissue from around the seed, and may even render the seed coat more permeable.

When seeds get larger, animal dispersers like ourselves generally pick them out and discard them rather than swallowing them. Something about the size of a watermelon seed is about the break point on swallowing versus picking out. Fruits with big seeds (grapefruit) or pits (inner part of fruit with enclosed seed) like peaches and mangos are no brainers. You can follow fruit eating monkeys through a rainforest and see, based on what they drop and defecate (don't follow too closely), that their choices are very similar to yours.

For some reason, probably having something to do with the way it was stored, the environmental conditions overroad the inhibitors and kicked these tomato seeds into premature germination, so here they are growing their way out of the fruit.

HT to a curious botanical colleague.