In the root zone of the soil-less culture, stress conditions such as low temperature, drought and high salinity can be easily introduced and controlled by applying physical and chemical characteristics of water. These stress conditions in the root zone cause depres-sions in root absorption and leaf photosynthesis and resultantly bring osmotic stress and oxidative stress in the plant body. The osmotic stress and the oxidative stress can induce the respective plant adaptive functions of osmotic adjustment and antioxidation. These plant functions can be expected to bring high quality and value-added vegetables enriched with sugars, functional amino acids, antioxidants etc., if the induced stresses are not so serious that the stress damages are not fatal without the extreme depression in growth. In this paper, two examples of the short term stress application only to roots for production of value-added vegetables are demonstrated. By the one week application of low temperature (5℃) stress only to roots of spinach plants (Spinacia oleracea L.), sugars, ascorbic acid and Fe²⁺ were significantly enriched in leaves. Furthermore, concentrations of harmful substances of NO₃^- and oxalic acid were extremely decreased. The two weeks salt stress treatment to roots of tomato plants (Lycopersicon esculentum Mill.) by applying the Muroto deep seawater at the stage of rapid fruit growth induced the osmotic adjustment and the antioxidation, which brought high quality tomatoes enriched with sugar, minerals, functional amino acids and good flavour without occurrence of extremely small-sized fruits and blossom-end rot. These verify that the short term stress application only to roots in the soil-less culture is reliable for production of high quality and value-added vegetables.

抄録全体を表示

Storage temperature for fruits is usually maintained constant at low level. In recent years, however, there has been much interest in heat stress application that reduces the quality loss of fruit during storage. In this study, dynamic optimization of heat stress application for reducing the water loss and respiration in fruit during storage was investigated using intelligent approaches. Over a temperature range from 15 to 40℃, the control process was divided into l steps (l =6). The dynamic change in the rate of water loss as affected by temperature was first identified using neural networks, and then the optimal combination of the l -step set points for temperature that minimized the rate of water loss (or respiration) was searched for through simulation of the identified model using genetic algorithms. A double heat stress application, such as T_opt={40, 15, 40, 15, 15, 15℃}, was obtained as an optimal value under the range of 15 ≤T≤40℃. The length of one step is 24 hours. With a single heat stress application, the temperature first rises to the highest level (40℃), which is maintained over a period of 24h, and then suddenly drops to the lowest level (15℃). This operation repeats two times in the double heat stress application. In particular, the sudden drop in temperature from the highest level to the lowest level provided lower values of the rate of water loss than maintaining the temperature constantly at the lowest level throughout the control process. These results suggest that the optimal combination of high temperature (heat stress) and low temperature allows to maintaining freshness and improving the quality of fruit during storage.

抄録全体を表示

In order to achieve plant production in a closed ecological life support system (CELSS) in space, environmental control is a key technology because the environment is completely artificial. One advantage of the CELSS in space is that each module's gas composition and total pressure can be regulated at an optimal level. For example, the nitrogen contained in air is not necessary for plant growth, and low oxygen concentration may enhance net photosynthesis by reducing photorespiration. Hypobaric conditions, obtained by reducing nitrogen and oxygen concentrations, could facilitate gas control, reduce construction costs, and simplify maintenance of modules on a lunar base and in plant production systems on Mars. This review summarizes previous papers and evaluates significant effects of total pressure on growth and development of higher plants, especially crops. Previous studies showed that photosynthesis and transpiration of plants were enhanced under low total pressures because gas diffusion rates increase at low total pressures. Spinach and lettuce in vegetative stages can grow normally under 25 to 50 kPa total pressures. Seeds of rice and Arabidopsis thaliana germinated at 25 kPa total pressure. Flowering was normal in Arabidopsis under hypobaric conditions. Seed growth of soybean and Arabidopsis under low total pressures with a low O₂ partial pressure was greater than under the atmospheric pressure with the same O₂ partial pressure. This indicates that O₂ concentrations inside siliques were maintained higher by the higher diffusion rates prevailing under hypobaric conditions. The results indicate that if total and partial pressures are controlled precisely, plants can grow normally in their life cycle from germination to harvest under hypobaric conditions.

抄録全体を表示

When placed in rooms, plants refresh the indoor environment, relax people's minds, and promote comfort. In anticipation of these effects, plants are becoming more commonly placed in indoor environments such as homes and offices. These effects are known as “green amenity”, and constitute a field in this journal, Science and High Technology in Agriculture. I have been conducting researches on green amenity for over 15 years, and received a prize from the Japanese Society of Environment Control in Biology in 2000 for “Researches on green amenity”.
Green amenity includes the following four effects: thermal regulation and comfort improvement, psychological effects, alleviation and healing of visual fatigue, and air purification. We are conducting experiments and researches on each of these effects. In addition, due to the increasing attention on horticultural therapy, which is primarily used for elderly people, we are also conducting experiments and researches on the psychological effects of horticultural therapy as an applied field of green amenity. In addition, guidelines that meet the increasing demand for comfort at offices are becoming necessary.
Herein, I outline our recent researches on the psychological effects of green amenity as well as their evaluation methods, specifically with regard to the following analyses:1) attachment developing from looking after plants, 2) effects of liking and growing plants on human psychology, 3) effects of growing plants from seedlings and bulbs on the psychology of elderly people, and 4) effects of ornamental foliage plants on the psychology of office workers.

抄録全体を表示

施肥量の違いがミズナの生育と硝酸イオン濃度に及ぼす影響を，同じアブラナ科で硝酸イオン濃度が高い葉菜類の一つであるコマツナを比較対象として検討した．施肥処理は大塚A処方0.5単位を標準区（S区）とし，1/4S区，1/2S区，S 区，2S区，3S区および4S区の計6区とした．ミズナの生育は4S区に比べ2S区～3S区が良好だった．一方，コマツナは施肥量の増加とともに生育量も増加する傾向がみられた．ミズナの硝酸イオン濃度はいずれの調査日においても施肥量の増加とともに高くなる傾向がみられ，硝酸イオン濃度に及ぼす施肥量の閾値はわからなかった．一方，コマツナの閾値は2S区～3S区に存在すると考えられた．さらに，播種後40日目に最も高くなったのはミズナとコマツナともに4S区で，一般的な値のそれぞれ約6倍と約2倍になった．SPAD値はミズナがコマツナより低かったが，ともに1/2S区以下とS区以上を境界としてSPAD値に差が認められた．以上の結果から，ミズナの生育と硝酸イオン濃度に及ぼす施肥量の影響はコマツナとは異なることが明らかとなった．さらに，ミズナの硝酸イオン濃度はコマツナに比べ施肥量により急激に高くなる可能性があり，コマツナよりも窒素施用量に注意が必要であると推察された．

抄録全体を表示

サンダーソニアのクローン増殖を目的として，生殖成長器官である花茎の頂端分裂組織からの形態形成に及ぼすサイトカイニンの影響を検討した．NAAとサイトカイニン（BAP，TDZ，あるいはCPPU）を組み合わせて添加した培地で培養した結果，NAA 0.0μMとTDZ3.2μM，NAA3.2μMとTDZ 1.0μM，NAA3.2μMとTDZ3.2μM，NAA3.2μMとCPPU 3.2μMを組み合わせた4培地区において，供試したすべての花茎の頂端分裂組織から多芽体が形成された．多芽体のなかには多数の微細な不定芽によって構成されているものがあり，それを分割することで，多芽体が増殖した．多芽体からはシュートの伸長がみられるとともに，伸長したシュートの基部には子球の形成が観察されたことから，サンダーソニアの花茎の頂端分裂組織をこれらの培地区で培養することによって，サンダーソニアのクローン増殖が可能となると判断された．

抄録全体を表示

ジニア（Zinnia elegance L. ‘Profusion cherry’）を対象として昼夜間温度差（DIF）環境下（+10 DIF（明期25°C/ 暗期15°C），0 DIF (20°C/20°C)，-10 DIF (15°C/25°C)）における下胚軸伸長成長量を画像解析を用いて定量的に解析を行ない，明暗期温度が与える影響について検討した。その結果，ジニアの一日の伸長成長量は，実験開始2日目で-10 DIF区で0.29 mm，0 DIF区で0.13 mm，+10 DIF区で0.05 mm，3日目ではそれぞれ0.27 mm，0.17 mm，0.09 mmとなり，DIF値が増加するにしたがって減少し，DIFに反応しない品目であることが明らかとなった。そこで，明暗期毎の伸長成長量を調べたところ，明期伸長成長量は2日目では-10 DIF，0 DIF，+10 DIFで0.07 mm，0.04 mm，0.04 mm，3日目ではそれぞれ0.08 mm，0.06mm，0.07mmとなり，DIF値に対してほとんど変化がないのに対して，暗期伸長成長量は2日目で0.19 mm，0.09 mm，0.01 mm，3日目で0.16 mm，0.10 mm，0.03 mmとなり，DIF値が増加するにしたがって顕著に減少することが判明した。DIF条件下における暗期温度はDIF値が増加するにしたがって減少するので（本研究の場合は，DIF値が-10 DIFの場合の暗期温度は25°Cであるのに対して，+10 DIFでは15°Cである），暗期温度の低減が暗期伸長成長量の減少の要因となっていると推察され，ジニアの伸長成長量調節のための基礎的な知見が得られたと考える。

抄録全体を表示