Growth Substances and Ions Absorption (1948)

The results of some experiments concerning the influence of growth substance on ion intake by plants are presented. Is has been found that the rate of ion intake is independent of low concentrations of growth substance. It is suggested that the intake takes place via the living processes. The regulation of the transport of glucose is mentioned as a possible direct function of the growth substance.

The intake of ions by the plant is a consequence of its reaction to the composition of the medium. As a base from which to start further research into this phenomenon, we suggested a working hypothesis founded upon the following concepts: — The ion absorption is a result of the differences in the physico-chemical activity of the ions of the periphery of the root and the ions of the medium. This difference in ion activity causes a flow of ions to move in the direction of the plant, which flow is kept going by transportation and inactivation of the ions taken up by the plant (pump-function).

A complication of the process in question arises from the adsorption of ions from the medium to the surface of the root (surface-function) (Schuffelen and Loosjes, Schuffelen). Energy is needed for the continuation of the pump-function and this is provided by processes taking place in respiration and in accumulation of organic material. It is consequently a function controlled by the living- processes (Hoagland and Steward, Lundegardh). The surface-function is of a more non-living nature and is regulated by the composition of the plasma of the root wall.

This plasma is highly important in connection with the study of the significance of the ion ratio of the medium in relation to plant growth, while the pump-function is related to the ion intake process as a whole. As plant growth substances play an important r61e in living processes it may be expected that the ion intake will also be influenced by auxin concentrations as suggested by Lundegrdh and others. Moreover, the fact that Veldstra considers the growth substances to act as transport (permeability) regulators encouraged us to examine the influence of some growth substances on ion absorption.
(Plant & Soil, 1948)

Zat Pengatur Tumbuh

Growth stimulators are exogenous natural organic compounds, which in very small draughts are able to influence significantly physiological process of plants growth and their development, not showing toxic effect in concentration  used and not being a nutrition source. Their activity is manifested in increased crop capacity, enhanced drought – and frost – resistance of vegetative plants, as well as in better disease resistance of plants (Karmanova et al., 2002).

At present there is an evergrowing trend to use preparations from the products of plant raw materials. In recent years scientists often appeal to study of self-protection mechanisms of plants in nature. Coniferous plants of Pinacea family produce many interesting substances, among which are those that serve as plant growth stimulators and protectors. The Siberian scientists have shown that the extract from the sum of triterpenic acids from Abies greenery effects the morphological plants indications similar to auxin: leaves become dark-green, roots length increases and crop capacity of many cereals and forage crops raises. The sum of triterpenic acids from Abies wood greenery was isolated by them for stimulator obtaining by extraction with organic solvent and further separation of acid and neutral part of extract by aqueous solution of alkali.

Kurva pertumbuhan tanaman

1. Growth Response Curves Liebig (c. 1860, German) (linear)

Y = mX + b,   where:  Y = yield; m = slope – i.e. rate of yield increase, a function of the environment and nutrient; X = amount of nutrient added; b = minimum yield, one would get this yield with no nutrient additions.

2. Mitscherlich (c. 1910, German) (Law of Diminishing Returns)

(1) dy/dx = (A-Y)C.  if integrate equation (1), then get (2) log (A-Y) = log(A) – cX, where:

A = maximum possible yield (theoretical); Y = actual yield.

dy/dx = slope – i.e. rate of yield increase, a function of the environment, the nutrient, and amount of nutrient already present. This value gets smaller as nutrient amount increases.

x = amount of nutrient added; c = constant.

3. Bray (c. 1920, U. Illinois) (soil interactions)

Started with Mitscherlich’s basic equation, developed: log (A-Y) = log(A) – c1B – cX, where:  A = maximum possible yield (theoretical); Y = actual yield.

dy/dx = slope – i.e. rate of yield increase. It is a function of the environment, the nutrient, and amount of nutrient already present. This value gets smaller as nutrient amount increases.

X = amount of nutrient added; c1 = constant that is for B; c = constant.

B = value explaining behavior of ‘immobile’ nutrients (e.g. K, P, Ca, Mg). The c1B term takes into account the reality that nutrients interact with soil and not all nutrients behave identically.

4. Baule (c. 1920, German mathematician, worked with Mitscherlich) (nutrient interactions)

Baule developed idea of “half-way points.” Using the identical relationship as Mitscherlich,

Baule concluded that: Y = A – A(1/2) # Baule Units, where:

A = maximum possible yield (theoretical); Y = actual yield.

Baule Unit= the amount of nutrient that when added results in moving Y (yield) one-half  way closer to A (maximum possible yield).

Faktor penentu pertumbuhan tanaman

“Growth is defined as the progressive development of an organism”

Setiap syarat tumbuh dapat membatasi hasil. Aturan minimum dari Liebig berlaku unsur hara, tetapi dapat pula diterapkan bagi syarat tumbuh yang lainnya. Pertumbuhan tanaman dibatasi oleh keberadaan hara yang paling terbatas jumlahnya, tanpa memperhatikan besarnya sediaan hara yang lainnya. Tugas petani adalah mengidentifikasi semua faktor pembatas hasil, dan menghilangkan atau meminimalkannya sehingga usahanya menguntungkan.

Faktor penentu pertumbuhan tanaman dapat dipilahkan menjadi 2 bagian yaitu:  Genetik (dakhili=internal) dan Lingkungan (khariji=eksternal).

Faktor Genetik

Perbaikan genetik dengan munculnya hibrida, varitas atau galur telah menunjukkan adanya peningkatan hasil panen pada tanaman jagung, gandum atau komoditas lainnya.

Tabel. Hasil panen jagung di USA pada tahun 1971-1973

Hibrida tahun

Panen buruk (kg/ha)

Panen baik (kg/ha)

1930

3.709

6.538

1940

4.464

7.544

1950

4.778

7.670

1960

4.902

8.550

1970

5.972

8.990

Tabel. Hasil panen gandum berbagai varitas

Varitas

Panen (kg/ha)

1926 (Marquis)

2.028

1935 (Thatcher)

2.230

1958 (Lee)

2.425

1967 (Chris)

2.735

1971 (Era)

3.623

Tanaman dengan hasil panen tinggi (high yielding) mengambil hara lebih banyak dibandingkan tanaman biasa. Tanaman demikian bersifat menguras hara. Jika ditanam pada tanah yang memiliki ketersediaan hara terbatas, maka hasil panen akan lebih rendah dibandingkan tanaman biasa.

Pada masa lampau dilakukan pemilihan varitas tanaman untuk berbagai tingkat kesuburan tanah yang berbeda. Sekarang hal tersebut tidak dikerjakan lagi, karena pada tanah yang  tidak subur dapat ditambahkan pupuk. Meski demikian tetap dilakukan upaya pemilihan tanaman misalnya: tahan terhadap pH rendah atau keracunan Al, atau terhadap kondisi garaman, atau tahan terhadap kekeringan.

Faktor lingkungan

“Environment is defined as the aggregate of all the external conditions and  influences affecting the life and development of the organism.”

Yang termasuk dalam faktor lingkungan adalah : Temperatur, Lengas, Sinar matahari, Susunan udara, Struktur tanah, Reaksi tanah, Biotik, Penyediaan hara dan Senyawa penghambat pertumbuhan.

  1. Temperatur: Temperatur merupakan ukuran intentitas panas.  Kisaran temperatur secara umum untuk makluk hidup: -35 0C  –  +75 0C; Tanaman pertanian : 25 – 40 0C. Temperatur ini mempengaruhi: fotosintesis, respirasi, permeabilitas dinding sel, penyerapan air dan hara, transpirasi, aktivitas ensim dan koagulasi protein.
  2. Lengas tanah : kadarnya dalam tanah sangat bervariasi: Jenuh air (saturated)– kapasitas lapangan (field capacity) – layu permanen (wilting point). Fungsi lengas antara lain sebagai : pelarut, media transportasi, bahan dasar H2O.
  3. Sinar matahari: aspek yang terkait dengan pertumbuhan adalah: proses fotosintesis, lama penyinaran dan periode tumbuh.
  4. Udara: diperlukan untuk respirasi dan sebagai bahan dasar CO2 dalam proses  fotosintesis.
  5. Struktur tanah : mempengaruhi ruang tumbuh akar dan imbangan udara-lengas.
  6. Reaksi tanah: berkaitan dengan ketersediaan hara, unsur meracun dan kehidupan mikrobia.
  7. Biotik: antagonisme atau sinergisme, jasad pengganggu: hama,  penyakit, gulma
  8. Penyediaan hara: mineral, tekstur, struktur, pH, bahan organik tanah, pemupukan, pengolahan tanah.  Perakaran tanaman dapat  dangkal, dalam, atau menyebar.
  9. Senyawa penghambat pertumbuhan: adanya limbah atau bahan beracun.