Plant hormones

Plant Hormone의 정의 Hormone 동물체내의 특정 장소에서 생산되어 다른 특정한 기관에 지속적으로 작용하여 변화를 주는 화학 물질의 총칭 극미량으로 작용이 가능하며, 그 자체가 에너지 대사 등의 기질로 사용되지 않는 조절물질 성장 호르몬은 몸의 성장을 촉진 난포 자극 호르몬과 황체 자극 호르몬은 정자 및 난자의 형성을 자극하고 남성 및 여성 호르몬을 만드는 데 관여 Plant Hormone 식물자신이 만들어 낸 미량으로 작용하는 생리 활성 물질, 정보 전달 물질로 식물에 보편적으로 존재하고, 그 물질의 화학적 본체와 생리작용이 밝혀진 것 공통점 : 특정한 활성상태를 촉발시키고 유지시킴. 차이점 : 분비기관과 표적기관이 명확하지 않고 이동경로가 명확하지 않음.

Plant Hormones 1) 식물 조직에서 생성되는 유기화학 물질 2) 생체의 기능 향상 3) 호르몬 작용 기관 및 조직이 다양 4) 주요 식물호르몬 옥신, 사이토키닌, 지베렐린,에틸렌, 아브시스산

PGR의 종류 Auxin Cytokinin Gibberellin Abscisic Acid Ethylene

1) Auxins Auxins are compounds that positively influence cell enlargement, bud formation and root initiation. They also promote the production of other hormones and in conjunction with cytokinins. Auxins affect cell elongation by altering cell wall plasticity. They stimulate cambium, a subtype of meristem cells, to divide and in stems cause secondary xylem to differentiate. Auxins act to inhibit the growth of buds lower down the stems (apical dominance), and also to promote lateral and adventitious root development and growth. Auxins in seeds regulate specific protein synthesis, as they develop within the flower after pollination, causing the flower to develop a fruit to contain the developing seeds. Auxins are toxic to plants in large concentrations; they are most toxic to dicots and less so to monocots. Because of this property, synthetic auxin herbicides including 2,4-D and 2,4,5-T have been developed and used for weed control. Auxins, especially 1-naphthaleneacetic acid (NAA) and indole-3-butyric acid (IBA), are also commonly applied to stimulate root growth when taking cuttings of plants. The most common auxin found in plants is indole-3-acetic acid (IAA).

옥신: 식물이 씨에서 발아하여 생장하는 데에는 여러 가지 조절물질이 필요한데 특히 줄기의 신장에 관여하는 식물생장호르몬 정단부의 세포 신장 촉진, 줄기 신장 (IAA, indol-3-acetic acid) 옥신은 인돌아세트산(IAA)으로 트립토판이라는 아미노산으로부터 합성되었다. 즉, 트립토판이 없으면 줄기의 생장점에서 옥신이 생기지 않는다.

2) Cytokinins Cytokinins (CKs) are a group of chemicals that influence cell division and shoot formation. They control the growth of stems, roots, and fruits, and convert stems into flowers They also help delay senescence of tissues, are responsible for mediating auxin transport throughout the plant, and affect internodal length and leaf growth. They have a highly synergistic effect in concert with auxins, and the ratios of these two groups of plant hormones affect most major growth periods during a plant's lifetime. Cytokinins counter the apical dominance induced by auxins; they in conjunction with ethylene promote abscission of leaves, flower parts, and fruits.

사이토키닌(CK) 개화 유도 및 어린 조직에 풍부, 세포분열 촉진(zeatin) 식물의 조직을 배양할 때 생장점을 떼어내어 배양하면 미분화된 세포덩어리인 캘러스(callus)를 만드는데 이때 사이토키닌을 처리하면 뿌리, 줄기, 잎으로 분화가 이루어진다.

3) Gibberellins Gibberellins (GAs) include a large range of chemicals that are produced naturally within plants and by fungi. Gibberellins are important in seed germination, affecting enzyme production that mobilizes food production used for growth of new cells. This is done by modulating chromosomal transcription. In grain (rice, wheat, corn, etc.) seeds, a layer of cells called the aleurone layer wraps around the endosperm tissue. Absorption of water by the seed causes production of GA. The GA is transported to the aleurone layer, which responds by producing enzymes that break down stored food reserves within the endosperm, which are utilized by the growing seedling. GAs produce bolting of rosette-forming plants, increasing internodal length. They promote flowering, cellular division, and in seeds growth after germination. GAs also reverse the inhibition of shoot growth and dormancy induced by ABA.

지베렐린(GA) 줄기, 뿌리 신장촉진 및 발아 촉진(GA3, gibberellic acid) 지베렐린의 작용은 신장촉진작용, 종자발아촉진작용, 개화촉진작용, 착과(着果)의 증가작용, 열매의 생장촉진작용 등이 있다.

4) Abscisic Acid Abscisic acid (ABA) is composed of one chemical compound normally produced in the leaves of plants, originating from chloroplasts, especially when plants are under stress. It acts as an inhibitory chemical compound that affects bud growth, and seed and bud dormancy. It mediates changes within the apical meristem, causing bud dormancy and the alteration of the last set of leaves into protective bud covers. It plays a role in leaf and seed dormancy by inhibiting growth, but, as it is dissipated from seeds or buds, growth begins. In other plants, as ABA levels decrease, growth then commences as gibberellin levels increase. Without ABA, buds and seeds would start to grow during warm periods in winter and be killed when it froze again. It accumulates within seeds during fruit maturation, preventing seed germination within the fruit, or seed germination before winter. ABA's effects are degraded within plant tissues during cold temperatures or by its removal by water washing in out of the tissues, releasing the seeds and buds from dormancy.

아브시스산(ABA) 세포 분열 억제 및 탈리현상 촉진 식물의 성장 중에 일어나는 여러 과정을 억제하는 식물호르몬으로 흔히 ABA라고 줄여서 말하기도 한다. 세스키테르펜의 일종으로 휴면 중의 종자·나무눈·알뿌리 등에 많이 들어 있으며, 보통 발아되면서 함량이 감소한다.

5) Ethylene Ethylene is a gas that forms through the breakdown of methionine, which is in all cells. Ethylene has very limited solubility in water and does not accumulate within the cell but diffuses out of the cell and escapes out of the plant. Ethylene is produced at a faster rate in rapidly growing and dividing cells, especially in darkness. New growth and newly germinated seedlings produce more ethylene than can escape the plant, which leads to elevated amounts of ethylene, inhibiting leaf expansion. As the new shoot is exposed to light, reactions by phytochrome in the plant's cells produce a signal for ethylene production to decrease, allowing leaf expansion. When a growing shoot hits an obstacle while underground, ethylene production greatly increases, preventing cell elongation and causing the stem to swell. Ethylene affects fruit-ripening: Normally, when the seeds are mature, ethylene production increases and builds-up within the fruit, resulting in a climacteric event just before seed dispersal.

에틸렌 과일의 성숙 촉진 에틸렌은 과일이 익는 속도를 증가시키는 것으로 알려져 있으며 농도가 클수록 과일은 보다 빨리 익는다. 바나나의 경우, 바나나 산지에서 덜 익어 푸른 것을 따서 저장, 운송하는데 이 과정에서는 환기를 적절히 해 에틸렌의 농도를 최대로 낮추어 익는 것을 늦추고, 판매 직전에는 에틸렌을 불어 넣어 바나나가 익도록 해서 시장에 내어 놓는다.

Seed Dormancy Plant hormones affect seed germination and dormancy by acting on different parts of the seed. Embryo dormancy is characterized by a high ABA:GA ratio, whereas the seed has a high ABA sensitivity and low GA sensitivity. In order to release the seed from this type of dormancy and initiate seed germination, an alteration in hormone biosynthesis and degradation toward a low ABA/GA ratio, along with a decrease in ABA sensitivity and an increase in GA sensitivity, must occur. ABA controls embryo dormancy, and GA embryo germination. Seed coat dormancy involves the mechanical restriction of the seed coat. This, along with a low embryo growth potential, effectively produces seed dormancy. GA releases this dormancy by increasing the embryo growth potential, and/or weakening the seed coat so the radical of the seedling can break through the seed coat. ABA affects seed coat growth characteristics, including thickness, and effects the GA-mediated embryo growth potential. These conditions and effects occur during the formation of the seed, often in response to environmental conditions.

Hormones and Plant Propagation Synthetic PGRs are commonly used in a number of different techniques involving plant propagation from cuttings, grafting, micropropagation, and tissue culture. The propagation of plants by cuttings of fully developed leaves, stems, or roots is performed by gardeners utilizing auxin as a rooting compound applied to the cut surface; the auxins are taken into the plant and promote root initiation. In grafting, auxin promotes callus tissue formation, which joins the surfaces of the graft together. In micropropagation, different PGRs are used to promote multiplication and then rooting of new plantlets. In the tissue-culturing of plant cells, PGRs are used to produce callus growth, multiplication, and rooting.