垂枝桃枝条发育形态和内源激素的关系

Relationship Between Morphology and Hormones During Weeping Peach (Prunus persica var.pendula) Shoot Development

以垂枝桃(Prunuspersica var.pendula)为试材,分析了垂枝桃枝条发育过程中生物学形态和内源激素含量的变化。直枝型枝条基角和延伸角极为接近,平均值分别为52.5°和52.0°;而垂枝型枝条基角和延伸角则分别为51.7°和92.9°。说明这两种类型芽萌发后的生长方向一致,直枝型枝条在生长过程中能维持原生长方向,但垂枝型在生长过程中发生向下弯曲。根的基角与枝条的延伸角有相关性,直枝类型和垂枝类型根的基角分别平均为78.3°和42.5°。倒置生长的垂枝桃枝条仍然表现为向重力生长,说明枝条下垂是受重力诱导的。直枝桃枝条中木质素含量高于垂枝桃,在枝条背上下两侧差异尤大。对内源植物激素含量的测定表明,直枝型枝条中的赤霉素含量由基部至梢部递增,在垂枝桃枝条背上侧赤霉素含量高于下侧,与木质素分布状况一致,赤霉素分布的不均衡是导致次生木质部发育不均衡的重要原因。垂枝桃梢端赤霉素含量较直枝桃更高,导致枝条先端生长快于次生木质部发育,使枝条无法支撑自身重量而下垂。外源GA3处理的垂枝桃枝条中IAA/GA3比例与CTK/GA3比例均显著增高,促进了垂枝桃枝条中部细胞分裂与木质部分化,使其表现直立生长。

Morphological and hormonal changes during the shoot development of weeping peach （Prunus persica var. pendula） were studied. The basal crotch and extended angles of shoots for the weeping form were 51.7° and 92. 9°, respectively; as compared to 52. 5° and 52.0° for the standard peach. This shows that the shoots of the two peaches started growth in similar angles, but the branches of the weeping form wep（ down as shoots get longer. The roots of weeping peach also grew downward with a crotch angle of 42. 5°, compared to 78.3° for the standard form. When weeping peach trees were placed upside down, the braches also grew down to the earth, indicating that the growth direction is dictated by gravity. The lignin content in the standard form is higher than in the weeping form which has much more lignin in the upper shoot than in the lower part. This suggests that the mechanical tissue of weeping peach has weaker support ability for its branches. Similar to the lignin distribution, GA3 content measured by ELISA increased from the base to the tip of a weeping branch where the gibberellins content is higher than the tip of a standard branch. This may result in that the tips of weeping branches grow faster than the development of second xylem, so the branches can＇t support their weight and weep downward. Treatment of braches of weeping peach by GA3 changed the GA3 content and distribution,increased IAA/GA3 and CTK/GA3 ratio, and promoted the cell division and development of xylem in branches, resulting in upright growth.