Hand leaf thinning for improvement of fruit coloration and quality is one of the most labor-consuming works in Korean apple cultivation. The study was aimed at investigating whether foliar application of two chelate compounds (Cu-EDTA, Fe-EDTA) could defoliate effectively ‘Hongro’/M.9 apple leaves and enhance fruit coloration and quality. At 30 days before harvest, foliar spray with two chelate compounds defoliated significantly the apple leaves. Chelate treatments did not affect the leaf chlorophyll content. High concentration of chelates decreased drastically photosynthetic rate of true leaves, and then it stayed in low levels, whereas low levels of chelates reduced sharply the photosynthetic rate but it was gradually restored over time. Cu-EDTA regardless of its concentration triggered higher defoliation compared to Fe-EDTA. Consequently, higher defoliation improved light interception of fruits and accumulated more anthocyanin. Particularly, Cu-EDTA could target mainly fruit cluster leaves which affect directly light interception of the fruits, i.e. more selective defoliants compared to Fe-EDTA. However, 3% Cu-EDTA rather defoliated excessively, accompanying with reduction of fruit weight and soluble solids. Therefore, our results suggest that 1% Cu-EDTA which defoliates properly the fruit cluster leaves could improve coloration and quality of ‘Hongro’/M.9 apple fruits.

Cytokinesis is the final event in the cell division. After cytokinesis, one parent cell divided into two symmetric daughter cells. Unlike somatic cell which is symmetrically divided, oocyte meiotic maturation is highly asymmetric division, producing mature ovum and polar body. Class III phosphoinositide 3-kinase (PI3K) has been known as a key molecular component that regulates cell cycle progression, autophagy and endosomal trafficking. However, emerging evidences suggest that class III PI3K and its interactors are involved in midbody abscission during cytokinesis. Here we showed that beclin-1, a key component of PI3K is required to regulate midbody abscission during oocyte asymmetric division. Beclin-1 was widely distributed during meiotic maturation forming small vesicles. However, these vesicles were not colocalized with autophagosomal marker LC3. Instead, beclin-1 was detectable at the midbody ring during cytokinesis. Depletion of beclin-1 showed various defects including the failure of cytokinetic abscission, spindle separation and chromosome decondensation. Similar phenotype was observed when class III PI3K activity was inhibited. Therefore, our results demonstrate that PI3K is essential for cytokinesis but not autophagy during oocyte meiosis.

Toward molecular understanding of flower senescence/abscission, we have identified a mutant, designated as dea1-1D (dealyed abscission1-1D), with delayed flower senescence/abscission syndrome from activation-tagged pools. Phenotypic analysis revealed pleiotropic effects of dea1-1D mutation including delayed flowering as well as smaller serrated leaves. Genetic analysis showed that it is a dominant mutation. Molecular analysis on the flower senescence syndrome indicated that dea1-1D might define novel regulatory branch of flower abscission, controlling expression of ethylene-responsive AP2 transcription factor. On the contrary, triple responses was not affected by dea1-1D mutant. Though the penetrance was not complete, the mutant phenoytpes was shown to be tightly linked with the T-DNA selection marker, BASTA-resistance. We identified the T-DNA insertion site through molecular cloning of the T-DNA flanking genomic DNA and found that a neighboring gene was overexpressed in the dea1-1D mutant. Together with gene expression analysis, we will discuss possible function of DEA1 during flower senescence and abscission.

Organ abscission is a programmed cell separation process that results in the detachment of an entire organ from a plant. Our goal is to understand the signaling pathway that regulates this physiological process. The receptor-like protein kinase, HAESA (HAE), and its paralog, HAESA-like 2 (HSL2), are both expressed in the floral abscission zones in Arabidopsis thaliana. Loss-of-function analyses of either gene do not show any phenotypical change, but the hae hsl2 double mutant shows an abscission-defect phenotype. Examination of the abscission zone by light and scanning electron microscopy showed that the abscission zone in the hae hsl2 appears structurally normal. The force required to remove the petals in wild type and hae hsl2 flowers was measured using a petal breakstrength meter. The force required to remove petals from the hae hsl2flowers at all stages of development was similar to that of wild type flowers that have not yet begun to abscise their petals. Taken together, these data support the role of HAE and HSL2 in the activation of cell separation, rather than differentiation of the abscission zone. Ethylene is also known to promote abscission; therefore we tested the ethylene-induced triple response and the effect of exogenous treatment on floral organ in the hae hsl2, revealing that HAE and HSL2 act independently of ethylene. This implies that the HAE is critical for floral abscission in concert with the action of HSL2.

아프리카 벼에 있어서 벼알과 소피경 사이에 형성되는 이층조직의 특이성에 따라, '부분이층', '불규칙이층' 및 '완전이층'의 품종을 각각 2품종씩 공시하여 유수형성 이후 유수와 영화의 신장에 따른 이층조직의 형성 및 발달과정을 해부형태학적으로 관찰하였다. 또한 출수후 수확기까지 등숙과정에 있어서 탈립성정도의 변화와 이층조직과의 관계에 대하여 검토하였다. 아프리카 벼의 유수와 영화는 출수전 15일 이후 급격한 신장을 보여 출수전 5일 경에는 출수기와 거의 동일한 길이로 신장되었다. 출수전 15일 경에는 작은 유조직세포로 구성된 이층조직의 형성부위를 인정할 수 있었는데, 부분이층의 외영쪽에는 이층조직의 형성부위를 인정할 수 없었고, 불규칙이층의 외영쪽에는 부분적으로 집단화되어 있는 소형의 유조직세포들을 관찰할 수 있었다. 출수전 10일경 이층조직 주변의 세포들은 세포벽이 식후하고 목화되어 1-2층의 유조직세포로된 이층조직을 더욱 뚜렷하게 구분할 수 있었는데, '부분이층'의 외영쪽에는 후벽조직속에 1-2개의 유조직세포가 혼재되어 있었고, '불규칙이층'의 외영쪽에는 불규칙하게 집단화된 유조직세포를 관찰할 수 있었다. 아프리카 벼에 있어서는 출수후 2주째 벼알의 등숙이 수확기와 거의 비슷하게 진전되었는데, 이때 이층구조의 붕괴현상 관찰할 수 있었으며, 또한 벼알과 소피경 사이의 인장강도도 수확기와 동일하게 저하하였다.

담배의 엽탈락, 품질 및 수량에 미치는 석회와 붕사의 영향을 알고자 시험한 결과를 요약하면 다음과 같다. 1. 엽탈락 이식후 40～80일에 많이 발생되며 불위엽에서 상위엽으로 진행된다. 2. 석회의 시용은 엽탈락을 조장하나 붕사는 엽탈락을 현저히 감소시켰다. 3. 석회의 시용은 전당, Lignin, 붕소함량을 감소시키며 붕사시용은 붕소와 Lignin 함량을 증가시킨다. 4. 붕사의 1년시용으로 엽탈락의 완전방지는 어려웠다. 5. 석회와 붕사의 시용량은 각각 120kg/10a,1.2kg/10a가 엽탈락방지와 품질, 수량성으로 보아 적정시용량으로 인정되었다.