INFLUENCE OF SOME ENVIRONMENTAL CONDITIONS ON THE GROWTH OF EXCISED ROOT TIPS OF WHEAT SEEDLINGS IN LIQUID MEDIA

White and Moebius attempted to grow immature ovules, and Tukey and Borger attempted to grow excised placental tissue, without marked success.

“White (1932, 89) and Moebius (1922, 105) have attempted to grow immature ovules and Tukey (1937, 114) and Borger (1926, 92) attempted to grow excised placental tissue without marked success.”

Very young seed primordia are made up entirely of meristematic cells and are easily removed with little danger of contamination and a minimum of trauma.

“Very young seed pri- mordia are made up entirely of meristematic cells and are easily removed with little danger of con- tamination and a minimum of trauma (White, 1932, 89 ; Moebius, 1928, 105; Molliard, 1921, 106).”

Glucose and fructose have been employed in some media, particularly those used for the cultivation of tissues of monocotyledonous plants, but with results which have not been entirely satisfactory.

“Glucose and fructose have been em- ployed in some media, particularly those used for the cultivation of tissues of monocotyledonous plants, but with results which have not been en- tirely satisfactory (Kotte, 1922, 51, 52; Robbins, 1922, 57 ; Robbins and Maneval, 1923, 59 ; Robbins and V. B. White, 1937, 178; Malyschev, 1933, 53, 54; White, 1932, 63, 1940, 172, 173).”

Root tips of wheat have an optimum temperature of about 27°C, and tomato nearer 30°C.

“Root tips of wheat have an optimum temperature of about 27° (White, 1932, 63), tomato nearer 30° (White, 1937, 265).”

Plant tissue cultures have an optimum temperature only slightly above room temperature, about 27°-30° C.

“Since plant tissue cultures are extremely sensitive to temperature fluctuations (White, 1932, 63, 1937, 265, 266) and have an optimum temperature only slightly above room temperature (about 27°-30° C), it is impor- tant that even the room used for routine stock cultures be air-conditioned, with faciilties for cooling in extremely hot weather.”

Plant tissue cultures are extremely sensitive to temperature fluctuations.

“Since plant tissue cultures are extremely sensitive to temperature fluctuations (White, 1932, 63, 1937, 265, 266) and have an optimum temperature only slightly above room temperature (about 27°-30° C), it is impor- tant that even the room used for routine stock cultures be air-conditioned, with faciilties for cooling in extremely hot weather.”

Cultures should never be exposed for long periods to direct light because they are extremely sensitive to high temperature and temperature changes and could easily become overheated.

“They should never be exposed for long periods to direct light as they are extremely sen- sitive to high temperature and to temperature changes and could easily become overheated (White, 1932(White, , 63, 1937, 265) , 265) .”

Water makes up approximately 97 per cent of the mass of all nutrients.

“Since water makes up approximately 97 per cent of the mass of all nutrients, while some other ingredients are required in amounts repre- sented by ten-thousandths of a per cent, the purity of the water used is of prime importance and can- not be overemphasized (White, 1932, 63, 1933, 141).”

Cultures are relatively insensitive to light and can be placed either in darkness or in diffuse light.

“Cultures are apparently for the most part relatively insensitive to light and can be placed either in darkness or in diffuse light (Robbins and Maneval, 1924, 258; White, 1932, 63, 1937, 265; Malyschev, 1932, 53, 54; Gautheret, 1935, 15).”

Such roots are very sensitive to differences in cultural conditions such as temperature, pH, osmotic value, concentration and proportion of nutrient salts, and carbohydrate supply; this sensitivity manifests itself either in change of growth habit or change in growth rate.

“Such roots are, in fact, very sensitive to differences in cultural conditions such as temperature, pH (White, 1932, 63), osmotic value (Bonner and Addicott, 1937, 42), concentra- tion and proportion of nutrient salts (White, 1933, 141, 1937, 143; Bonner and Addicott, 1937, 42), carbohydrate supply (White, 1932, 63, 1940, 172, 173), etc.; this sensitivity manifests itself either in change of growth”

A solution of calcium hypochlorite containing 1 per cent chlorine gives fairly satisfactory seed sterilization if seeds are shaken in it for 15 to 30 minutes, then washed in sterile distilled water.

“A solution of calcium hypochlorite containing 1 per cent chlorine will give fairly satisfactory re- sults (Wilson, 1915, 455;White, 1932, 63) if seeds are shaken therein for 15 to 30 minutes, then washed in sterile distilled water and placed in Petri dishes.”