農業と科学　令和5年5月

本号の内容

§Melon and cucumber with magnesium
カリウムの欠乏症状と再移動
Former Graduate School of Natural Science and Technology, Okayama University
桝田　正治
No § Soil - No.21
「土は生きている」といわれるのはなぜ？
－土は生き物なのか
前 ジェイカムアグリ株式会社
北海道支店　技術顧問
松中　照夫

　

　

メロンとキュウリのマグネシウム，カリウムの
欠乏症状と再移動

Former Graduate School of Natural Science and Technology, Okayama University
桝田　正治

Introduction.

野菜の生理障害について，筆者は発生部位と生育段階ならびにその発生要因を一つの表にまとめて示した⁷⁾。それから約20年経った現在においても，それらの症状の要因に新しい知見は加えられていない。

　このことは近年，野菜の生理障害があまり大きな問題となるには至っていないことを示唆する。種子繁殖性の野菜では，新品種の生育特性や連作に伴う病害の研究が多く生理学的研究そのものが少なくなったように感じる。栄養繁殖性のサツマイモ，サトイモ，ジャガイモ，ニンニク，イチゴなどはウイルスフリー原種を保存し，それから増殖させ種苗として市販されるが，通常，栽培者が１，２年繁殖していると新しくウイルスに感染してしまい，外見上の症状からは，病的あるいは生理的としてその要因を見分けることが難しくなる。勿論，マグネシウム，カルシウムの欠乏や拮抗阻害ならびに微量要素の欠乏によるものも少なくない。
　Mg欠乏症は微量の亜硝酸ガスやアンモニアガスによって引き起こされる障害にも時には類似すること，さらには光化学オキシダントやハダニの害と酷似するものも多く，その要因をすぐには判断しにくい場合が多い。

　The former gas disorder tends to occur in greenhouse cultivation, especially with the heavy use of organic fertilizers such as oil cake and chicken manure. In addition, the gas disorder is also more likely to occur in open field cultivation of direct-seeded vegetables such as spinach, radish, and komatsuna, because their leaves are in contact with the ground surface. The mechanism of gas generation has already been clarified, and it is necessary to control the acidity of soil pH and the amount of nitrogen fertilizers, especially ammonia-form nitrogen fertilizers, to suppress gasification.

　後者については，図１の①～③に示したように，光化学オキシダント障害，強光や高温障害などがあげられる。これらは一般に知られる写真④のメロンの葉脈間クロロシスとも類似していることがある。このメロン着果節葉に発生する症状とMg欠乏との関連性を本稿では論じようとするものである。光化学オキシダントは工場や自動車などから大気中に排出される窒素酸化物（NOx－ノックスと読む）や揮発性有機化合物が紫外線を受けて生成される物質（オゾン（O₃）やパーオキシ・アセチル・ナイトレート（PAN）など）が動植物の細胞に障害をもたらす。

　The morning glory shown in the photo (1) in Fig. 1 is a typical example of such a disturbance, and was an indicator plant for photochemical smog in the 1970s, which the author also investigated at a farm affiliated with Kyoto University about 50 years ago. At that time, I learned that taros were sensitive to photochemical smog among vegetables. Even recently, when cucumber leaves temporarily encounter intense light in early summer, the veins of the leaves become mottled and whitened on the following two days. This phenomenon is probably caused by the inability of the reactive oxygen species (ROS) scavenging system to instantaneously process the excess light energy, but no evidence has been obtained.

　In the Earls melon shown in Photo (2), high temperatures and temporary intense light also cause overnight discoloration of some of the spaces between the veins of the leaves. Although the earl melon is an extremely high temperature tolerant crop (no damage occurs on the leaves on the opposite side of the strong light even at 43°C), the high temperature combined with strong light causes damage to the leaves.

　Unlike nitrite, ammonia gas, photochemical oxidants, or high light damage, the mite damage shown in photo (3) is characterized by blurred leaf symptoms, and as the disease progresses, many mites can be seen on the underside of the leaves with the naked eye. However, the initial symptoms are similar to those of Mg deficiency and are difficult to distinguish. In particular, it is better to suspect mite damage first rather than physiological disorders in vegetables at the beginning of the hot season.

Mg deficiency symptoms and component migration in melon defoliation and cucumber

(1) Overview of melon defoliation

　一般にウリ科作物では生育中期以降，特に果実の肥大が進む頃になると近傍の葉の葉脈間にクロロシスを発現することが多い。1980年代には各地でプリンスメロンの葉枯れ症が多発し多くの試験場での研究報告はMg欠乏によるものとした。そんな中で兵庫県農業総合センターの津高¹²⁾は葉枯れ症がK欠乏によって生じていると報じた。筆者の知る限りではK欠乏とした論文は後にも先にもこれが唯一である。

　藤本²⁾はハウスメロンの葉位別Mg含有率を正常株と葉枯れ症株について調査し，図２の結果を得ている。果実は第13節～16節に発生した側枝に着果させ，下位葉から上位葉まで主茎節位の葉分析を行ったもので，13節～16節のMg含有率は正常株では0.3％以上，発生株では0.2％以下となっていることが分かる。この結果から，同氏は葉枯れ症の発現レベルは，葉中Mg含有率で0.2％レベルにあるとし，葉枯れ症は果実の肥大成熟に伴って葉のマグネシウムが果実へ転流し，その結果，葉の葉脈間が黄化し，やがて黄褐色を呈して枯れるが，このタイプのものは成熟の目安とされることもあるほどで収量，品質にほとんど影響しないと述べている。

　筆者４）も自根キュウリの生理障害，褐色小班葉が0.19％以下で発生すること，欠乏症状を呈した葉のMg含有率は正常葉のそれに比べて確かに低いことを認めている。しかし，これらの結果は，葉から果実へマグネシウムが移行することを示すものではない。従来，マグネシウムは移動しやすい成分とされているが^{３，10，13）}，本当に移動しやすい成分なのであろうか？　

(2) Difficulty of component transfer within the cucumber tree

　First, the author compared the changes in the components of hydroponic cucumbers, especially magnesium, with those of other components. The author replaced the culture medium of cucumbers (main branches at 22 nodes and lateral branches at 3 nodes) grown in the standard culture medium with tap water, and investigated the dry matter weight and content rate of leaves and roots at the 5th node over time. Nitrogen and phosphorus decreased significantly in the dry matter content of the roots (61% after 4 days of water treatment), and potassium and magnesium decreased further (74% and 82% after 8 days of treatment).

　一方，葉においても窒素，リン，カリウムは大きく減少した。特に，リンとカリウムの減少率が著しく，それぞれ処理８日後には当初の60％，63％となった。これに対して，カルシウムとマグネシウムは，わずかに減少するに過ぎなかった⁵⁾。勿論，処理期間中に光合成により乾物重は増加する。その時の乾物率から葉における含有量を求め処理開始時を基準に相対比として示したのが図３である。

　In the roots, calcium did not change at all, and the rate of decrease was total N=K>P=Mg>Ca. On the other hand, in leaves, calcium and magnesium did not change at all, and the rate of decrease was P=K>total N>Mg=Ca. The fact that there was no change in magnesium, which is considered to move frequently, indicates that magnesium in cucumber leaves is a less mobile element than nitrogen, phosphorus, and potassium, at least in comparison to nitrogen, phosphorus, and potassium, considering that the nutrient removal from the solution (tap water) was short, only 8 days.

　(3) Magnesium sprayed on individual cucumber leaves does not move even on those leaves.

Next, cucumber plants were picked and double-trimmed, and magnesium was removed from the culture solution when the plants reached approximately 70 cm in height, and then 1% MgSO4, Mg(NO3)2, or MgCl2 solution was applied to one of the double-trimmed plants four times every 2 days. completely suppressed in all treatments (control: it occurs in trees without spraying). The fact that the effect of MgCl2 application did not differ between the front and back sides of the leaves suggests that the Mg applied to the leaves enters the cells through the cuticle, where it is transformed into various forms.

　The sprayed leaves themselves remained green, but the leaves of the upper and lower nodes showed chlorosis (photo omitted). This indicates how difficult it is for the sprayed magnesium to move.

　In order to further understand the difficulty of Mg translocation in individual leaves, we identified one medium-sized leaf that was expected to develop chlorosis and sprayed a 1% MgSO4 solution into it four times every other day by pressing an open-bottomed paper cup against a portion of the leaf. The results are shown in Figure 4.

　Sprayed areas remained green, while unsprayed areas exhibited typical intervein chlorosis. The Mg content in these sites is shown in Table 1.

　It is clear that the water-soluble Mg in sprayed sites A-1 and B-2 is about 6 times higher than that in unsprayed sites A-2 and B-1, and the content rate of the unsprayed site is the same as that of the whole-leaf unsprayed site, which was established as a control, so at least the sprayed Mg is not mobile in the individual leaves.

　Despite the difference in leaf color between the sprayed and unsprayed sites, there was no difference in the magnesium in the chlorophyll backbone, i.e., 95% methanol-soluble Mg. This suggests that the amount of magnesium constituting chlorophyll is too small to be measured by ordinary instruments.

(4) White and green ring leaves of cucumber are induced by ammonia-form nitrogen.

　接ぎ木キュウリ〈台木はカボチャ〉の白変葉が，1970年代後半から高知，宮崎で多発し十数年にわたり多くの研究者がその原因の究明にかかわった。当初，この症状はMg欠乏によるとする報告が多く発表されたが，これは，いわゆる黄化（クロロシス）ではなく白色壊死（ネクロシス）することから，Mg欠乏だけでは説明できない現象であった。多くは葉縁が緑色に保たれていることから’グリーンリング葉’と称され，激しい時は一夜のうちに褐変，光が当たると白変が形成される。このような葉の発生要因を，高知県園芸試験場の松本ら⁸⁾は，見事に解明したのである。簡単に要約すれば以下のようになる。

　At that time, methyl bromide was used as a soil disinfectant in greenhouse cultivation. Oil cake, an organic fertilizer, was applied to the soil. The oil cake is converted to ammonia-form nitrogen by the action of microorganisms (ammonia-forming bacteria). Ammonia nitrogen is converted to nitrate nitrogen by nitrate-forming bacteria, and under low soil temperatures, the activity of the nitrate-forming bacteria is low (it is generally known that nitrate-forming bacteria are less sensitive to low temperatures than ammonia-forming bacteria), so the concentration of ammonia nitrogen increases. Furthermore, in soils treated with methyl bromide, the activity of nitrate-forming bacteria is weakened and the accumulation of ammonia nitrogen becomes more pronounced. Even if magnesium is present in the soil, its absorption is inhibited by antagonism when ammonia nitrogen is high. The greening of cucumber leaves is caused by an excess of ammonia nitrogen in the soil and inhibition of magnesium absorption.

　Nevertheless, the author still felt that it was necessary to reproduce the symptoms observed in farmers' greenhouses in order to prove the factors that induce white discoloration of cucumber leaves, so he repeated trial and error in hydroponic cultivation of self-rooted cucumber and grafted cucumber. As a result, we found that white discoloration and green ring leaves appeared on cucumbers on pumpkin rootstocks when the concentration of ammonia nitrogen and magnesium in the nutrient solution were increased and decreased, respectively (Figure 5).

　The technical term "interveinal necroticleaves" was first introduced in the revised Glossary of the Horticultural Society of Japan (2004), and green ring leaves were defined as a part of interveinal necroticleaves.

(5) Leaf damage and variation in Mg and K content with fruit set in melons - magnesium is sure to be re-migrated.
　is it?

Generally, when melons approach harvest time, chlorosis appears on the leaves near the fruit. This has long been a good indicator of harvest time. Textbooks state that this symptom is caused by the transfer of magnesium from the leaves to the fruit. I think I also learned this in a college course. In the case of Aalsfevorit, a slight yellowing between the veins of the leaves begins around 40 days after fruit set and becomes more intense around 50 days, when the leaves begin to brown. Is this a symptom of magnesium transfer from the leaves to the fruit?

　To investigate the presence of fruit and the degree of leaf damage, fruit node leaves were collected from each plant at 40, 50, and 60 days after fruit set and analyzed 70 days later6) . As shown in the right side of Figure 6, female flowers are attached to the first node of the lateral branch (cotyledon) extending from the 13th node of the main stem. The leaves in the vicinity are A, B, and C. Their shapes and colors are shown on the left. The upper panel shows the leaf color of a plant that removed fruit 40 days after fruit set (no fruit for 30 days), and the lower panel shows the leaf color of a plant that kept fruit until the end (70 days).

　As can be seen from the photo, when the leaves are picked at 40 days, all the leaves remain green, but if not, the leaves are deformed, with chlorosis between the veins and necrosis at the leaf margins. The symptoms are more pronounced in the fruiting node leaves. The fruiting period was set as long as 70 days in order to clarify the relationship between the fruiting period and the presence or absence of fruit. The magnesium, calcium and potassium contents of these leaves are shown in Table 2.

　Magnesium values varied little in the 1.1% to 1.2% range, regardless of whether the fruit was present or not.
カルシウムは若干低下する傾向にある。これに対して，カリウムは果実が長く存在するほど葉での含有率は低下し，70日間果実を残した株は40日目で除いた株の1/2以下となった。西村ら⁹⁾も着果時から経時的に葉分析を行いMg含有率は低下するどころか，むしろ徐々に高まることを明らかにした(図７)。

　Usually, leaves begin to turn yellow around 40 days after fruit set, and this change can also be detected by chlorophyll values (Figure 8). The leaf color is darkest on the 15th day of crossing, and then fades rapidly.

　In the Vegetable Horticulture Laboratory (Prof. Tadao Masuda) before the author was appointed to Okayama University, most of the research themes seemed to be set on melons. The data on magnesium, calcium, and potassium were extracted from the thesis of five years at that time and plotted by component. Figure 9 shows these data.

　As we will see, magnesium and calcium levels tend to increase gradually with fruit size, while potassium levels clearly decrease. Although intervein chlorosis and leaf margin necrosis would have appeared at 50 to 60 days after crossing, the relationship between the phenomena appearing on leaves and the analytical values has not been discussed. Observation of leaves in the vicinity of fruit set shows that intervein chlorosis caused by Mg deficiency in melons gradually intensifies as the harvest period approaches, so the view that leaf magnesium is transferred to the fruit is reasonable in nature and not at all surprising.

　However, there is no evidence to date that magnesium is transferred to fruits. The Encyclopedia of Agricultural Technology in the Rural Electronic Library (National Institute of Agro-Environmental Sciences) also states that magnesium is a mobile component that is transferred from leaves to fruits during fruit enlargement and ripening, and that deficiency symptoms may appear in the leaves around fruits.

Conclusion

　Vegetable nutrient physiology, especially nutrient deficiency, is often studied under two conditions: whether or not the same symptoms occur when one component is removed from the complete culture medium, and whether or not the same symptoms occur when other components are increased without removing the component. As shown in Figure 10, it is difficult to attribute leaf deficiency symptoms to a single component because of the interactive effects of ions on nutrient absorption in the roots.

　植物の根は，アニオン群，カチオン群から養分を選択的に吸収するが，木部液でのイオン総量〈meq〉は，プラスイオンとマイナスイオンで釣り合っている。土中にはNa＋, Cl－, HCO3－などを含め多種の微量要素イオンも存在する。なお，カチオンでは一価が二価よりも吸収されやすいとされ，それらの拮抗作用も知られている（NH4＋は筆者の栽培経験から挿入)。キュウリの白変葉はカボチャ台木で，かつNH4-N過剰下のMg欠乏により生じ，Mg濃度 が少し高いとグリーンリング葉になりやすい。つまり，白変葉は二つの要素により引き起こされる生理障害であり，一夜にして壊死症状を呈することから，筆者はアンモニアが直接関与している可能性が高いと推察している。

　A similar phenomenon is also observed in tomato lintel disease. It is well known that tomato lintel disease is caused by Ca deficiency, but severe gangrene appears at the fruit apex when Ca deficiency under NH4-N excess is present. The chlorophyll decay and potassium retrotranslocation are also likely to cause the damaged leaves at the fruiting node of melons.

　いずれの成分においても果実への再移動に関しては放射性トレーサーを用いてそのエビデンスを得る必要がある。Bukovacら¹⁾は，葉面散布した28Mgは45Caと同様に移動しにくいと記している(ただし，放射性Mgについてはデータ無し)。本稿のキュウリ個葉の散布実験と分析値からマグネシウムは隣の細胞にすら移動しにくいことが確認できた。

　最近，田野井¹¹⁾は，総説「植物のミネラル輸送研究最前線」において，Mg２＋トランスポーター遺伝子（MGT）のファミリーがシロイヌナズナ，イネでそれぞれ9個，トウモロコシで12個報告されているとし，それらのマグネシウムの輸送機構について解説しているが，メロンの葉におけるMGT発現量が散布したマグネシウムによって増大しなければ，もしくは，もともと葉におけるMGT機能が微弱であればマグネシウムはその部位に止まり移動しないのも当然と言える。メロン果実近傍の葉の葉脈間クロロシスはクロロフィルの崩壊によって生じているが，葉緑体でフリーとなったマグネシウムが果実に移動しないのもMGT遺伝子の発現量が関係しているかも知れない。

　Considering that, in general, about half of the magnesium in mature leaves is present in chloroplasts, some of which is chlorophyll-constituting magnesium, a small amount must be at issue with respect to retrotranslocation. However, it is not reasonable to assume that the free magnesium produced by chlorophyll decay is transferred back to the fruit, based on previous experimental results.28Magnesium has a short half-life of approximately 20 hours, so the tracer method is an essential tool for kinetic analysis, even with experimental limitations.

　Finally, one more question: why does chlorosis occur on the leaves near the fruit as it nears harvest time? If there is no fruit, it would not occur. At this time, some signal must be sent from the fruit to the leaves. What does this signal mean for the melon?

References

１．Bukovac,M.J. and S.H.Wittwer. 1957.
　　Absorption and mobility of foliar applied nutrients.
　　Plant Physio. 32：428－435.

２．藤本順子．2008．
　　園芸作物における栄養障害診断手法の開発と防止対策に関する研究．
　　島根農技研報. 8：1－45．

３．Jacob,A. 1958.
　　Magnesium: The fifth majorplant nutrient. 34-54.
　　Staples Printers Limited，Kingdom.

４．桝田正治．1984．
　　接ぎ木・自根キュウリの高K培地と高NH4-N培地で発生するMg欠乏症の差異．
　　農業及園芸59：1051－1053．

５．桝田正治．1989．
　　キュウリ葉におけるマグネシウムの欠乏症と移動の難易．
　　岡山大学農学報74：7－14．

６．桝田正治・金沢孝美．1993．
　　メロン着果節葉のカチオン含有率と養分欠乏症．
　　園芸学会中四支部大会要旨集32：31p.

７．桝田正治・寺林 敏．2003．
　　生産技術. 図説野菜新書．矢澤 進(編)．97－151．
　　朝倉書店．東京．〈131pに記載〉．

８．松本満夫・上杉郁夫・柳井利夫：1981．
　　施設栽培における接ぎ木キュウリのMg欠乏症（グリーンリング症)．I.
　　MB剤による硝化抑制が養分吸収とグリーンリング症に及ぼす影響．
　　高知農林報．13：1－10.

９．西村安代・福元康文・島崎一彦．2004．
　　アーメロン（Cucumis melo L.）の葉内無機成分に及ぼす着果の影響．
　　生物環境調節，42：137－146．

10．嶋田典司．1976．
　　マグネシウムの生理作用．土壌肥料作物栄養大辞典（第３版)．102－105．
　　養賢堂．東京．

11．田野井慶太朗．2021．
　　マグネシウムの輸送機構．
　　日本土壌肥料学雑誌．92：108－113．

12．津高寿和．1982．
　　プリンスメロンの葉枯れ症の原因と対策．
　　農業及園芸57：1162－1166.

13．山崎 伝．1975．
　　微量要素と多量要素〈第７版〉．175－183．
　　博友社．東京．

　

　

No Soil - No. 21
「土は生きている」といわれるのはなぜ？
－土は生き物なのか

前 ジェイカムアグリ株式会社
北海道支店　技術顧問
松中　照夫

　In this issue, we turn our attention to the soil itself. It is the soil that stably supports agriculture. The soil is the place where food that protects our lives is produced, and at the same time, it nurtures the lives of various living creatures. For this reason, it is often said that "the soil is alive" in awe of it. Why is this so?

1. Is soil a living thing?

　When asked again whether soil is really "alive," that is, whether it is a living thing, not many people would say that soil is a living thing.

　Living organisms in the general concept are multicellular organisms. To be a multicellular organism, it must satisfy the following three requirements: (1) differentiation and growth, (2) reproduction and heredity, and (3) autonomy in response to environmental changes (Okajima, 1989). However, no one would think that soil has parents who grow up, raise their children, and die by inheriting their genetic elements. Soil is alive" is merely a metaphorical expression of soil. We should be careful not to confuse soil with living beings out of respect for it.

　But even if it is a parable, the expression "the soil is alive" does not fail to capture our hearts. Why is that?

2. soil has properties similar to the autonomy of living things

　Soil has a property that gives a sense of the autonomy that living things have over their environment, i.e., the ability to maintain their own state of health in the face of external stimuli. This is the buffering power of soil.

　Let's take a look at the buffering capacity of soil specifically. Hydrochloric acid and sodium hydroxide are dropped onto the soil as an acidic substance and an alkaline substance, respectively. This means that the soil is stimulated from the outside. As shown in Figure 1, in the case of pure water (H₂O), the pH changes greatly to the acidic side and to the alkaline side with only a small amount of drop.

　一方，土Aと土Bのどちらも，純水より変化の幅が小さい。つまり，土は純水より緩衝力が大きいのがわかる。ただし，有機物の少ない土Aは，有機物の多い土Bよりも変化の幅が大きく，したがって緩衝力は小さい。土の有機物は，酸性の原因である水素イオン（H+）やアルカリ性の原因である水酸イオン（OH－）を静電気的に保持する能力を持つ（土の静電気的なイオン保持能については，昨年の２月号の第９回を参照)。このため，有機物がそれらのイオンを保持して動きを抑え，外界からの刺激をやわらげることができる。土Bのほうが土Aよりも緩衝力が大きいのは，土の有機物含量の違いに基づく。このような土が持つ緩衝力は，生き物の自律性とよく似ている。

　However, the buffering capacity of the soil is not the only reason why the soil is said to be "alive. The activities of living creatures living in the soil are often invisible to our eyes, and appear to us as if they were performed by the soil itself. This is another major factor that makes us feel that the soil is alive.

3. proof of life of living creatures - soil respiration

　The fact that compost fed to the soil becomes nutrients for crops, and that leaves that fall on the soil in the fall and kitchen scraps disappear eventually if they are buried in the soil, are all the result of decomposition of organic matter by soil organisms.

　When soil organisms decompose organic matter such as compost, fallen leaves, and garbage, carbon dioxide (CO₂) is released as one of the decomposition products. This is called "soil respiration" because it resembles animal respiration. It is as if the soil is breathing. However, this is only a proof of the activities of living creatures living in the soil, not that the soil itself is breathing.

4. organic matter decomposition is a cooperative play among soil organisms

　Using the fallen leaves mentioned above as an example, let us take a look at the beautiful interplay between soil organisms as they decompose organic matter (Fig. 2).

　Fallen leaves (plant remains) on the soil surface do not change significantly when they remain dry. However, once they are wetted by rain, bacteria (bacteria) and fungi (filamentous fungi) attach to them and soften the plant remains to some extent.

　Then, large soil animals such as earthworms, borers, and sowbugs appear and feed on the plant remains, pulverizing them and dragging them and their remains into the soil. Medium-sized soil animals, such as mites and stoneflies, then take charge, feeding on the dragged organic matter and taking nutrients into their bodies, and excreting the unwanted material as feces.

　Bacteria and fungi feed on the excreted feces and the remains of plants that have been dragged into the soil, eventually transforming them into carbon dioxide, water, and inorganic substances. The inorganic matter produced by this process is absorbed by the roots as nutrients for the plants growing there. Thus, a cycle of nutrients is established. Of course, the same mechanism applies to animal remains as it does to plants.

　The various material changes that occur in the soil include changes involving soil organisms. Therefore, when we talk about material changes in the soil, if we blur the distinction between the function of the soil and the function of living creatures in the soil, we confuse the two.

5. distinguish between the workings of the soil and the workings of living things.

　The expression "the action of the soil" does not mean that the soil has a "will (purposiveness)" like a living creature and that the soil itself actively works by its own will. The expression "the soil supplies nutrients to the crop" is also inappropriate, because the soil itself does not intentionally supply nutrients to the crop. When the crop selects and absorbs the nutrients it needs, such as cations, from among the various nutrient ions dissolved in the water (soil solution) in the soil, the balance of the electro-neutral principle (equal charge of cations and anions) is upset. Various reactions take place in the soil to restore the imbalance, and cations are released into the soil solution to maintain the electroneutrality principle.

　This is the phenomenon described as "the soil supplying nutrients to the crop. This reaction is also governed by a certain principle (in this case, the principle of electro-neutrality in solution), and there is no room for the free will of the creature.

　I would like to understand the true meaning of the parable "the soil is alive" after distinguishing the function of the soil and the creatures in the soil.