Anatomical Structure Of Main Plants And Its Environmental Adaptations In The Hilly-gullied Loess Platrau Region

Soil erosion is serious in the hilly-gullied Loess Plateau, and environmental factors, such as water, nutrient and light are uneven distribution. Plant leaves are very sensitive to environment, so they have different kinds of anatomical structures to adapt to the special environment in this area. In this study, leaf anatomical structures of 59 species in five erosion environments on slop-gully system on three vegetation zones were analyzed. The objective of this study was to explore characteristics of plant leaves and evaluate environmental adaptabilities of different species. The main results are as follows:1) Most of the dicotyledonous plants had isolateral leaves in the 49 species. Some species had isobilateral leaves, such as, Caragana intermedia, Glycyrrhiza uralensis, Robinia psendoacacia, Astragalus scaberrimus, Oxytropis discolor, Oxytropis gracillima and Artemisia gmelinii were total-palisade type; Heteropappus altaicus, Astragalus melitoloides and Artemisia giraldii were double-palisade type; Artemisia capillaris was ring-palisade type. Artemisia capillaries, Artemisia leucophylla, and Heteropappus altaicus had air chambers around their vascular bundles. Lespedeza davurica had a layer of mucilage cells in its spongy tissue. Glycyrrhiza uralensis, Hippophae rhamnoides and Robinia psendoacacia also had mucilage cells in their vascular bundles of midrib.2) In the ten species of monocotyledonous plants, Bothriochloa ischcemum, Setaria viridis, Phragmites australis, Cleistogenes hancei, Cleistogenes squarrosa and Cleistogenes chinensis were C4 plants, Carex lanceolata, Leymus secalinus, Stipa grandis and Stipa bungeana were C3 plants. There were different thickness of cuticles on upper and lower epidermis. Most of these species had bulliform cells in their upper epidermis, and the locations and sizes of bulliform cells were different among different species. There were three or four big vessels in the big vascular bundles of monocotyledonous plants and they arranged in “V”-shaped. There were always airways under the “V”. There were large air chambers in mesophyll of Carex lanceolata and these air chambers were alternate arrangement with vascular bundles.3) Different species had different adaptabilities to environment. Most of the dicotyledonous plants had big palisade/spongy and tissue structure tense ratio; only two indexes(upper cuticle thickness and vessel diameter) of monocotyledonous plants were different significantly amomg three vegetation zones. Dicotyledonous plants had thin epidemics, thick leaves and large vessels on hilltop. The increase of thickness of palisade tissue and leaves of total-palisade type plantsm, such as Astragalus scaberrimus, Glycyrrhiza uralensis and Artemisia gmelinii, were the biggest in forest steppe zone. The differences of Stipa bungeana among five erosion environments were small.4) The 49 species of dicotyledonous plants were divided into seven categories by Q cluster analysis and the ten species of monocotyledonous plants were divided into four categories.Different plants had diffenent adaptive strategies. Some plants stored water through succulent leaves, such as Cirsium setosum; some plants reduced water loss through thick protective tissues, such as Syringa oblata and Pulsatilla chinensis; some plants increased photosynthesis and water use efficiency through developed palisade tissue and degenerative sponge tissue, such as total-palisade type plants and double-palisade type plants; some plant reduced water loss through linear leaves and stored water though developed water storage parenchyma, such as Artemisia capillaries; some plants adapted to arid environment though developed mucilage cells, such as Lespedeza davurica; some plants stored water through thick leaves, such as Leymus secalinus; some plants reduced water loss though stomatal crypts, such as Stipa bungeana and Stipa grandis; some plants reduced water loss though leaves rolling and stored water by bulliform cells, such as Bothriochloa ischcemum and Setaria viridis; some plants enhanced air exchange though developed air chambers to increase photosynthesis, such as Carex lanceolata.