Conifers, or cone-bearing trees, evolved to have needles that retain more water and seeds that could hang out until there was enough moisture to take root. It may not seem like it, but needles are leaves. Instead of shedding every fall, though, needles can last three or four years!
Conifers in many ways are more primitive than flowering, broad-leafed trees that evolved more recently. But their needles still offer some nifty advantages over leaves—especially in tough climates or soil conditions:.
Read More. The needles hold several adaptive qualities that allow them to survive growing in areas that challenge most plants, such as places with heavy snowfall or where soils become very dry.
These leaf adaptations make evergreen conifers remarkably resilient in the face of conditions that might kill their deciduous broadleaf cousins. Some of these adaptations serve multiple purposes, like preserving water and protection from the cold. Needle-type leaves have a number of advantages when it comes to preserving water. Although it may seem counter-intuitive, considering the needle shape doesn't seem conducive to the collection of water on leaf surfaces like broad leaves might accumulate.
However, needles have pit-like stomatae -- holes through which trees exchange water and gasses -- that collect water and bring it into the leaf. Furthermore, these needles are covered with a waxy coating, preventing water loss through transpiration. Because evergreen conifers tend to grow in areas where snow falls, needles have adapted to reduce damage from the accumulation of snow.
Because needles are narrow, it's difficult for snow to remain on the leaves, and it falls to the ground.
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We also thank Mr. Wei-Tao Jin for his help on the phylogeny reconstruction. You can also search for this author in PubMed Google Scholar. XQW conceived the study. HD and XQW designed the study. HD performed most of the laboratory experiments and the data analysis.
All authors have read and approved the manuscript. Correspondence to Xiao-Quan Wang. Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Diverse morphologies of Pinaceae leaves. Ads, adaxial side; Abs, abaxial side. SEM micrographs of sclereids from leaves of Pinus krempfii a , Pseudotsuga menziesii b and Nothotsuga longibracteata c.
Red arrows indicate the sclereids. Sclereids of Pinus krempfii shown in Additional file 2 : Figure S2a. Sclereids of Pseudotsuga menziesii shown in Additional file 2 : Figure S2b. Sclereids of Nothotsuga longibracteata shown in Additional file 2 : Figure S2c. Phloroglucinol staining of xylem in the needlelike leaves of Cedrus deodara a , Picea smithiana b , Pinus armandii c and Pinus tabuliformis d. Stomatal conductance and transpiration rate for needlelike and flattened leaves under two gradients of irradiance.
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Du, H. The flattened and needlelike leaves of the pine family Pinaceae share a conserved genetic network for adaxial-abaxial polarity but have diverged for photosynthetic adaptation. BMC Evol Biol 20, Download citation. Received : 02 July Accepted : 21 September Published : 07 October
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