Effect Of Water Stress And Salt Stress On The Seed Germination And Seedling Growth Of Peltophorum Dubium

Peltophorum dubium (Spreng.) Taub. is a tree unique to Cattinga, a vegetation in dry areas in Brazil. P. dubium is considered as a rare and drought resistant species. It is the kind of glycophyte subject to salt stress with a narrow salinity threshold, owing to the long-range brine irrigation. Its environment is influenced gradually by salt stress. Therefore, its endurance is paid more and more attention to. The experiment are mainly studying the germination and seeding growth of primed seeds under water stress and salt stress, especially water stress, and the Putrescine's ease function to salt stress. The result indicates:1. During the early phase of seed germination and seedling growth of primed seeds Inhibition process of P. dubium seeds primed in Captan and PEG solutions shows that there is no rule to the radio of seed germination and the speed of it, and the seed in this case could be sensitive to aging treatment. The temperature doesn't affect largely the speed of inhibition, so the method of primed seed is dipped in distilled water for twelve hours.2. P. dubium can retain the radio of seed germination more than 60% at -1.0Mpa, showing it has strong drought resistance, erratically drought stress is the primary reason; Neither priming in Captan nor in PEG and in KNO₃ do no good in P .dubium seed germination under different drought stress, which shows it has adapted ecologically to the not regular drought stress as its inherent ecological adaptation, that is, ecological evolution.3. .NaCl, CaCl₂, KCl, Na₂SO₄ are four different solutions that have different effects on seeding growth of primed seeds., incorporate in stem length, root length, cotyledon weight, stem net weight, root net weight and the radio of the weight of stem and root and so on . As a whole, the trend is that the length of root and stem is reducing gradually with the increased osmosis potential; owing to the inhibition to the root and stem improves with the increased osmosis potential; its length is opposite to its weight .The weight of cotyledon is increasing gradually with the increased thickness in most cases, the result may be selectively adopted to salt iron. The radio of the length and the weight between in cotyledon and in the whole is corresponding to the degree of stress, which is in favor of root system getting into the deeper to alleviate the stress. However, the amount of living and the length in root under no stress is less than that under salt stress. This can indicate its ecologically adaptable capacity is lower to salt stress.4. P. dubium seedling growth was affected by salt stress in solution of NaCl, KC1 CaCl₂, and Na₂SO₄. The paper have found out that CaCl₂ is the highest degree in the stress to seeding growth of primed seeds, the next is NaCl and Na₂SO₄,the lowest one is KCl. Ca²⁺is higher in the naturally growing environment of P. dubium, this may be the primary cause that P. dubium is not fit to salt stress.5. Putrescine can regulate the germination and seeding growth of primed seeds under salt stress, the accommodation is different as the category of salt and the thickness is different.When the osmotic potential was OMPa, the length of root and stem, the dry weight of root and stem was higher than Putrescine was not added to the solution. So without the condition of salt stress on seedling growth was eased when Putrescine was added; To the stress of NaCl,, Putrescine can play an good part in regulating inside-0.6—-1.2MPa.,the function of it could do better in KC1 than in NaCl, its modulation is lower in CaC^ and in Na2SC>4.; As a result, Putrescine can be considered as an important regulator in the germination and seeding growth of primed seeds under salt stress to apply in resuming the population.6. P. dubium has formed a well ecological mechanism to be adaptable to the drought stress by reason of not regular moisture in nature. Not only P. dubium seedling and its seeding growth but also seed capsule can be tolerant to drought stress, the high radio of seed germination and the low speed of it is its express of well adapted to salt stress, but when the people cultivate it, its seed capsule usually is reduced by using oil of vitriol or dipping in the distilled water. When P. dubium is in the early phase of seed germination and seeding growth of primed seeds, it has a certain adaptability to salt stress, but the stress still inhibit the seeding growth as a whole. Therefore, the main reason for being in danger in the population of P. dubium is excessively exploring the resource, destroying living environment, and making gradually the crude soil salting.7. The key technical means of resuming the population of P. dubium is including the disposal of oil of vitriol, dipping in the distilled water, and utilizing Putrescine.