The shape and the structure of the leaves of conifers, called needles, are different. They are narrow, elongate and either rhomboid, semi-circular or elliptical in cross-section in order to limit transpiration as much as possible.
Between the xylem and the phloem, there is a thin layer, called the cambium, consisting of several layers of thin-walled cells which, during the growth period, rapidly divide to form new wood on the inside and new phloem on the outside.
The primary vein divides the blade into two, generally equal, halves. In some woody plants, however, the halves are not identical, especially at the base, and these are termed asymmetric (elm, hackberry). In other species the leaf may have several veins branching out from the base (maples); such leaves are usually palmately lobed.
The strip of compact summer wood is easily distinguished from the strip of the following year's spring wood so that on a stump we can clearly see the yearly growth, in the form of annual rings, and thus easily determine the age of the felled tree.
The pine leaves live for a shorter time than those of the spruce; and leaves of a spruce growing at low elevations live longer than those growing in harsh conditions.
The process is slow and gradual, and the tree sappears unchanged. Only the amount of needles on the ground beneath i serves as an indication of its shedding rate.
Between the xylem and the phloem, there is a thin layer, called the cambium, consisting of several layers of thin-walled cells which, during the growth period, rapidly divide to form new wood on the inside and new phloem on the outside.
The primary vein divides the blade into two, generally equal, halves. In some woody plants, however, the halves are not identical, especially at the base, and these are termed asymmetric (elm, hackberry). In other species the leaf may have several veins branching out from the base (maples); such leaves are usually palmately lobed.
The strip of compact summer wood is easily distinguished from the strip of the following year's spring wood so that on a stump we can clearly see the yearly growth, in the form of annual rings, and thus easily determine the age of the felled tree.
The pine leaves live for a shorter time than those of the spruce; and leaves of a spruce growing at low elevations live longer than those growing in harsh conditions.
The process is slow and gradual, and the tree sappears unchanged. Only the amount of needles on the ground beneath i serves as an indication of its shedding rate.
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Where appropriate, a traditional style of garden planning can be used in your garden.
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