Seeds

Since this is the time of year when most plants in my part of the world are setting seeds, I thought I'd post a few images of these wonderful objects. This is one of the ripening seeds from my runner beans Phaseolus coccineus, with the testa and one of the cotyledons removed, revealing the embryonic plant inside. The cotyledons contain the store of proteins, carbohydrates and lipids that will provide sustanance for the germinating seedling until its first true leaves unfurl and begin to photosynthesise. In this image you can see that the rudiments of the venation in those first true leaves, that will transport sugars to other part of the young seedling, have already formed in the embryo. The embryo is attached to the cotyledons at its hypocotyl and the embryonic root points downwards and to the left. 

There's a heavy crop of oak (Quercus spp.) acorns in this part of Durham this year - it's a mast year. Oak acorns - technically nuts - germinate soon after they fall to the ground, anchoring themselves via their root but then suspending further growth until spring, when the shoot forms. If you are planning to plant oak trees, it's best to sow the fresh acorns soon after they fall.

Once seeds germinate their root needs to spear into the soil quickly, driven by the hydraulic force inside expanding cells. Here you can see the glistening root cap of a maize (corn) Zea mays seedling, producing the mucilage that lubricates its path between the abrasive soil particles. Further back, you can see the forest of root hairs, each a single elongated epidermal cell that makes intimate contact with the surface of soil particles and absorbs water and soluble minerals. Each root hair has a short life span, of perhaps a day, and new hairs are formed constantly behind the advancing root tip; collectively they constutive a vast absorptive surface.

Scarlet Runner bean Phaseolus coccineus

Growing vegetables in the flower border has become fashionable in recent years but here's a vegetable that always been easy to appreciate for its decorative value - the runner bean. What other climber has such vivid flowers and also makes a nutritious addition to Sunday dinner? Scarlet runner bean hails from the mountainous regions of Guatamala, Mexico and Panama so it's travelled a long way on its journey to the gardens and allotments of Britain .... and changed a good deal along the way. The seeds and pods are monstrous compared with the diminutive wild versions and the pods have been bred to reduce the stringy tissue and parchment layer in the pod wall that would make wild pods shatter and release seeds as they dry out. Runner beans are usually grown as annuals (I've just sown what I hope will be an early crop) but they are perennials in the wild and if you can keep the roots frost-free through the winter they'll produce a second year's growth, albeit with inferior pod production. If you are of a curious nature and fancy some amateur plant breeding you could try crossing French beans with runner beans, by carefully removing stamens from French bean flowers with fine tweezers before they shed pollen and then pollinating the flowers with runner bean pollen a day or two later. The cross works with French beans as the female parent, but not the other way about.