When K
+ is deficient, root growth is poor because K
+ functions in photosynthate
translocation into roots. Then, due to poor root growth, nutrient absorption
decreases; thus, a negative feedback loop is established (Fig. 1.29). These trends
have been confirmed in the tropical peatlands of Kalimantan in central Indonesia as
well (Matsubara et al. 2002). In this area, soil δ
15 N was !1.0, while that of various
plants was 1.0; this ecosystem also absorbs nitrogenous nutrients through atmospheric nitrogen fixation in the same way as the tropical peatlands of Thailand.
Carbohydrate translocation to roots is highly dependent on leaf position and K
+
-
levels. Carbohydrates are supplied from the lower leaves to the roots in cereal crops
and legume crops (Fig. 1.30) (Yamada et al. 1997, 2002). In root crops and mainstem
plants (such as oil palm), K
+ is important for carbohydrate translocation from leaves
to roots (or underground organisms) because K
+ cotransports carbohydrates into
roots (Fig. 1.31) (Marschner 1995).
In conclusion, high root growth and activity are maintained by K
+
-nutrient
absorption.
Sustr et al. (2019) reviewed the functions of potassium in roots and noted that
potassium is an essential macronutrient that has been partly overshadowed in root
science by nitrogen and phosphorus; they summarized (1) the role of K
+ in root
growth, root system architecture development, cellular functions, and specific plant
responses to K
+ shortages. K
+ transport is crucial for its physiological role; (2) the
links between K
+ transport and cell expansion, membrane trafficking, auxin homeostasis, cell signaling, and phloem transport; and (3) the crucial mechanisms of the
plant stress response that are regulated by K
+
-related mechanisms.
40 cm depth
Very poor root growth even in 40 cm
layer
Supporting roots
(do not need much O 2 )
Lateral roots for
nutrient absorption
(need large amounts of O 2 )
Fig. 1.29 Poor root growth due to the negative feedback loop of K
+ deficiency
46
M. Osaki et al.
+ is deficient, root growth is poor because K
+ functions in photosynthate
translocation into roots. Then, due to poor root growth, nutrient absorption
decreases; thus, a negative feedback loop is established (Fig. 1.29). These trends
have been confirmed in the tropical peatlands of Kalimantan in central Indonesia as
well (Matsubara et al. 2002). In this area, soil δ
15 N was !1.0, while that of various
plants was 1.0; this ecosystem also absorbs nitrogenous nutrients through atmospheric nitrogen fixation in the same way as the tropical peatlands of Thailand.
Carbohydrate translocation to roots is highly dependent on leaf position and K
+
-
levels. Carbohydrates are supplied from the lower leaves to the roots in cereal crops
and legume crops (Fig. 1.30) (Yamada et al. 1997, 2002). In root crops and mainstem
plants (such as oil palm), K
+ is important for carbohydrate translocation from leaves
to roots (or underground organisms) because K
+ cotransports carbohydrates into
roots (Fig. 1.31) (Marschner 1995).
In conclusion, high root growth and activity are maintained by K
+
-nutrient
absorption.
Sustr et al. (2019) reviewed the functions of potassium in roots and noted that
potassium is an essential macronutrient that has been partly overshadowed in root
science by nitrogen and phosphorus; they summarized (1) the role of K
+ in root
growth, root system architecture development, cellular functions, and specific plant
responses to K
+ shortages. K
+ transport is crucial for its physiological role; (2) the
links between K
+ transport and cell expansion, membrane trafficking, auxin homeostasis, cell signaling, and phloem transport; and (3) the crucial mechanisms of the
plant stress response that are regulated by K
+
-related mechanisms.
40 cm depth
Very poor root growth even in 40 cm
layer
Supporting roots
(do not need much O 2 )
Lateral roots for
nutrient absorption
(need large amounts of O 2 )
Fig. 1.29 Poor root growth due to the negative feedback loop of K
+ deficiency
46
M. Osaki et al.