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1.脯氨酸(Proline)在植物中的分布 植物體內游離的脯氨酸主要分布在光和器官和生殖器官.在其他組織和器官中,脯氨酸的量相對較少.陳托兄在研究不同類型抗鹽植物水平游離脯氨酸的分配時,對三種類型的植物進行了分析:稀鹽植物,泌鹽植物,拒鹽植物.稀鹽植物中游離脯氨酸的含量很低,拒鹽植物游離脯氨酸的量較高,泌鹽植物游離脯氨酸的量介于二者之間.不過他們有一個共同的特征:游離脯氨酸多集中的代謝旺盛的器官和生殖器官,這是因為植物在受到脅迫時會優先?;ふ廡┢鞴?這也是植物在長期進化過程中自然選擇的結果.</p>

2.脯氨酸(Proline)在鹽脅迫下累積的生物學意義 植物在鹽脅迫情況下一般會采取兩種方式來累積脯氨酸:一種是當植物遇到滲透脅迫時,高鹽的脅迫信號通過各級信號途徑傳遞,使得與滲透調節物質相關的基因表達(如脯氨酸合成酶基因),導致脅迫誘導的基因產物(累積),從而維持細胞內水分平衡.一種方式就是將液泡中儲存的脯氨酸運輸到胞質中使細胞中脯氨酸急劇增加來抵抗高鹽環境.

脯氨酸作為一種理想的滲透調節物質有很多特性:脯氨酸的分子量小,是一種極易溶于水的氨基酸;在生理pH范圍內不帶靜電荷;能被細胞膜所保持;幾乎不引起酶解構的變化;生成迅速,并能高累積足以引起調節作用的量.這些特性使脯氨酸在植物抗逆境脅迫中有重要作用: 脯氨酸可以調節細胞的滲透勢:鹽脅迫情況下,植物細胞會因為細胞內水勢降低而容易失水.因此植物能否保持正常生長狀況,關鍵在于能否維持體內的水分平衡.脯氨酸作為一種可溶性較強的氨基酸,在正常的pH內不帶電荷.在滲透脅迫情況下,脯氨酸利用其較強的吸水能力來增強細胞的持水能力,同時脯氨酸和其他一些可溶性物質的累積可以降低細胞的水勢,進而驅使水分進入細胞或降低水分從細胞中流出,為細胞膨脹提供了膨壓. 脯氨酸可以穩定蛋白:

脯氨酸在植物體內不帶電荷,又具有偶極性,它不會插入到蛋白質分子疏水相中引起蛋白質變性.在滲透脅迫情況下,它可以和酶相互作用從而?;さ鞍椎慕峁購凸δ?維持酶的活力.脯氨酸還可以改善細胞膜的水環境,增強膜結構的穩定. 脯氨酸可以作為氮素和碳架,在脅迫解除后為植物提供能源,有助于植物恢復正常生長.此外,脯氨酸在植物受害的過程中,可能作為氨的解毒劑.脯氨酸代謝的過程中產生NADP+(NADP+是戊糖磷酸合成NADPH的必要成分),使NADP+/NADPH比例升高.從這一點可以看出,在鹽脅迫下,脯氨酸累積可以為植物細胞的光合作用和呼吸作用的氧化還原提供NAD和NADP.

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1. Distribution of Proline in plants Free proline in plants are mainly distributed in light and organs and reproductive organs. In other tissues and organs, the quantity of proline are relatively few. Chen's brother in the study of different types of salt resistance of plant level when the distribution of free proline, analyses the three types of plants: dilute salt plant, secrete salt plant, from salt plant. Dilute salt content of free proline in plants is very low, from high salt plant the amount of free proline, secrete salt plant the amount of free proline between the two. But they have one common feature: the metabolism of free proline concentration more exuberant organs and reproductive organs, this is because the plants priority protection when under stress These organs. This is also the result of natural selection over a long period of time. / p>

2. Proline (Proline accumulation under salt stress the biological significance of plants under salt stress condition generally adopt two ways to accumulation of Proline: one kind is when plants meet with osmotic stress, high salt stress signals through various ways, making gene expression related to osmotic regulation substances (such as Proline synthase gene), causes the stress induced gene product (cumulative), so as to maintain water balance in the cell. A way will be stored in the vacuole Proline transport to the dramatic rise in the cytoplasm of the cell Proline to resist high salt environment.

As an ideal osmotic regulator, proline has many characteristics: the molecular weight of proline is small, and it is an amino acid easily soluble in water; No static charge in the physiological pH range; Can be retained by cell membranes; Almost no change in enzyme deconstruction; These characteristics make proline play an important role in plant resistance to stress and stress: Proline can regulate cell osmotic potential: salt stress conditions, plant cells is replaced because of the reduced water in cells. So the plants can maintain normal growth, the key lies in whether to maintain water balance in the body. As a kind of soluble proline stronger amino acids, with no charge within the normal pH. In the case of osmotic stress, proline is using its strong ability of absorbing water to enhance cell water-holding capacity, at the same time, the accumulation of proline and other soluble substances can reduce cell water potential, thus driving water into cells and reduce the water outflow from the cells, provides the cell expansion turgor pressure. Proline can stabilize protein:

Proline in plants in vivo without charge, have dipolar again, it won't be inserted into the hydrophobic phase caused by protein denaturation of protein molecules. In the case of osmotic stress, it can and interaction in order to ensure the structure and function of the protein enzymes, to maintain the vitality of enzyme. Proline can also improve the water environment of the cell membrane, increase the stability of the membrane structure. Proline could be used as nitrogen and carbon frame, provides the energy for plants, after stress relieve helps plants returned to normal growth. In addition, in the process of proline in plants suffer, probably as ammonia antidote. Proline metabolism in the process of producing NADP (NADP It can be seen from this that under salt stress, proline accumulation can provide NAD and NADP for the REDOX of photosynthesis and respiration of plant cells.


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