Residents of the middle lane do not need to explain and tell what the needles on the trees are. Everyone knows that these are leaves of spruce, pine, larch. They know that even in winter, pines and spruce do not dump their foliage, so they are called evergreens.
The world around: what are the needles in the history of the development of the planet
Already in the Paleozoic era (almost 300 million years ago) huge forests of coniferous vegetation (initial forms) covered the planet. Then the reproduction of these forms of vegetation occurred from seeds lying directly on the leaves (hence the classification of conifers as gymnosperms).
The beginning of the Jurassic period (220 million years ago) after global changes in the planetary climate made it possible to show conifers their beauty and rare adaptability to a temperate climate.
Over the past period (from Jurassic to modern), conifers have lost privileges, but still dominate in some areas with a temperate climate. Thus, in the territory of the former USSR, forests consisted of almost seventy-five percent of coniferous forests (approximately fifty percent of them were larch, twenty-one were pine (ordinary and cedar), and only about two were shade-tolerant conifers (fir and spruce).
What are needles?
Leaf-like (leaf-like) organs of conifers are well adapted to annual environmental changes - to temperature fluctuations (hot in summer, frosty in winter), to changes in the amount of moisture (excess in the spring-summer-autumn period, lack in winter). What are the needles of pines, spruce, fir, pseudo-burr? These are stiff, rather small (compared to angiosperm leaves) tree needles that have a small evaporating surface, but in which photosynthesis reactions nevertheless undergo.
Such a familiar spruce
The tetrahedral spruce needles of the spruce grow individually, spreading throughout the tree branch. They are very elastic with not very noticeable (even to the touch) edges, but each tip is even sharper - a small prickly needle with a sharp-sharp tip.
What are spruce needles in a section (section)? This is the wrong rhombus. The lower corner (downward) is the largest, the middle vein is located in it (the needles are a modified leaf). This design feature makes it possible for needles to be stiff (prickly and durable). And an additional two layers of cells immediately below the epidermis (outer layer) make the needles of spruce even more durable. The length of the needles in different types of firs can be from one to one and a half centimeters.
Each needle is covered with a thick layer of wax coating - this is a cuticle. In fir trees, the cuticle layer is the largest, and the higher the gas contamination in urban conditions (an unfavorable factor for these plants), the thicker the wax coating, in which the exhaust gases dissolve. Spruce thus saves itself, but lives in urban conditions much less than in natural conditions - the cuticle decays, the needles fall.
Pine needles
This plant belongs to the largest group of evergreen conifers. Her long leaves of the first year grow like a spruce - one by one. The second year is interesting in that new shoots (twig-needles) come out of each sinus of the previous year, there can be from two to five (this is inherent in different species). In pine needles fall along with branches.
Pine ordinary - the most common in Europe and Asia - two-coniferous. Banks pine (also found in Europe and Asia) has short needles, slightly more than spruce (from two to four centimeters), and they are equally stiff. The North American bog pine is distinguished by the length of the needles - its soft needles grow up to forty-five centimeters.
The American continent is the birthplace of three-coniferous pines.
Five-conifers grow in both Europe and America. Weymouth pine - the most exotic species among them. Long soft needles are preserved in this plant only at fifteen centimeters of the tips of the drooping branches. Crows are very fond of these needles in winter, peck them like a vitamin supplement.
Our Siberian and Far Eastern cedar is a five-coniferous pine. The length of the needles in it does not exceed five centimeters.
