Effect Of Nutrient Deficiency On Growth And Development Of Avocado Seedling

Avocado (Persea Americana Mill.) is known as a famous tropical and subtropical fruit trees, also a woody oil crops. Avocado is not only nutritious but also valuable in application and economic. As far as we known, research of cultivation,preservation, physiology and fertilizer ratio was reported on avocado, but which of nutritional diagnosis of the seedling was absence. And it is necessary for promote the efficient cultivation of avocado seedlings and the development of avocado industry.This experiment was taken avocado seedlings as a material,treated with different nutrient deficiency treatments. The phenotypic characteristics, related growth indexes and physiological indexes of the photosynthetic physiology were observed by appearance diagnosis, rapid diagnosis of chlorophyll meter and element vector diagnosis. This experiment provides the theoretical basis for the diagnosis and fertilization of avocado, for promote a rapid way for the development of avocado plantation. The results are showed as follow:(1)A11 treatments of nutrient deficiency showed negative effect on the seedlings growth. All of the nutrient deficiency seedlings’ leaves have appeared deficiency symptoms, which perform in under-sized plant, stems of small, and leaves turn into yellow or white, the top of the mature leaves turn into yellow, brown patches and necrosis or the plant grow poorly and development abnormally. For example, in the absence of nitrogen, the mature leaves of the upper part of the leaf become yellow,with burning patches, and the top leaves turn yellow or exsiccation. When the phosphorus element was deficiency, the old leaves have yellow patches or the edge of leaves become curling. When potassium element deficiency, the top of the old leaves turn yellow, and the surface of the top of the blade is out-of-flatness. When the calcium deficiency ,the leaves are small, and leaf vein rube does. When the magnesium element deficiency, young leaves involute and the tip bitter of old leaves involution. When the sulfur deficiency , young leaves curl mildly, and become reddish,and the edge of top mature leaves curl. When the iron deficiency , young leaves turn white and involute, top part of mature leaves with reseda patches. In the absence of boron element, the middle part of the leaves are yellow and curly, and the leaves turn yellow along the veins reticulation. In the absence of -Mo element, young leaves turn into curling and malformation, old leaves have small macula. In the absence of Mn element, the surface of the top mature leaf is not smooth and the veins are prominent.In the absence of -Zn element, the color of the mature leaves become shallow. In the absence of -Cu element, the young leaves and surface of the top mature leaves are out-of-flatness. In the absence of -Cl element, young leaves are not smooth, become pale and malform.(2)The Nutrient deficiency of avocado seedlings growth and physiological indexes were affected. Nutrient deficiency seedlings showed significant decreases in height, ground diameter, effective leaf number, leaf area, leaf fresh weight and leaf dry weight compared with CK. But the nutrient deficiency has a different influence on the growth index of avocado seedlings. In the same treatment time, the combined effects of trace elements were relatively large, such as the lack of Mn and Cu elements. And the lack of elements in S,N on avocado seedlings growth and physiological effect is relatively obvious. But the impact of major elements on avocado seedlings chlorophyll content of SPAD is relatively large. The nutrient deficiency indexes on avocado seedlings, the most major in height is -Mn treatment,which growth rate is only 36% CK. In the deficiency in nitrogen has the greatest effect on the ground diameter, leaf number and chlorophyll, and the diameter, leaf number and chlorophyll decreased by 61.9%, 66.8% compared with CK. Copper deficiency has the greatest effect on leaf area,and leaf area was only 47.4% compared with CK. The effect of calcium deficiency on leaf length, fresh weight and dry weight are the largest, and the diameter, leaf number and chlorophyll decreased by 34.5%,40.4%, with CK, they are significantly lower than that of whole grain treatment.(3)The different treatments on the seedlings were seriously affected photosynthesis. The nutrient deficiency of avocado seedlings’ stomatal conductance,transpiration rate and water use efficiency were decreased, which reduced the net photosynthetic rate, but intercellular CO2 concentration increased. In the absence of various elements, the lack of major elements on the net photosynthetic rate, stomatal conductance, transpiration rate, water use efficiency is more obvious, and the stomatal limitation value is relatively small. The nitrogen deficiency had the greatest influence on photosynthetic parameters, the net photosynthetic rate was 83.6% lower than that of CK, stomatal conductance was reduced by a factor of 61.5%, transpiration rate was reduced by a factor of 66.9%, and water use efficiency was reduced by a factor of 50%.Therefore, the nutrient deficiency of avocado seedlings will hinder the growth of leaves, reduce the leaf photosynthetic performance. In this experiment the lack of -N,-Mn, -K, -P influence on Photosynthetic Characteristics of avocado is most obvious,the net photosynthetic rate,stomatal conductance,transpiration rate and water use efficiency were significantly lower than that of CK.After the vector, analysis of leaf nutrient,we can know that the first factor to limit the deficiency is the lack of elements, and the the second limiting corresponding elements are different.It can be seen that the lack of nutrients will cause some synergistic and antagonistic effects among the elements of the nutrient in the seedling,and it may also affect the content of other nutrients when some elements are missing.Thus the nutrient deficiency will have certain effect on the avocado seedlings’growth and physiological. In the same time, the nutrient deficiency in -Mn,-Cu trace elements,-S amount element,-N major element, will have effect on the avocado seedlings’ growth and physiological obviously, and the avocado seedlings are most sensitive to trace elements, which plays an important role in the growth process. The lack of these nutrients should be avoided in production practice.